Synopsis  

Gastrointestinal endoscopy applies technology to further the diagnosis and management of disorders of the digestive tract. This chapter provides a broad overview of the wide variety of endoscopes and accessories now available from multiple manufacturers.

 Gastrointestinal endoscopes   

Gastrointestinal endoscopes are highly evolved and sophisticated flexible instruments with a broad range of diagnostic and therapeutic applications. Endoscopes incorporate advanced video, computer, material, and engineering technologies [1–4]. The development of modern flexible gastrointestinal endoscopes followed the development of fiber optics and subsequently the charge-coupled device (CCD). Modern endoscopes continue to use fiber optic light guides to transmit light to the endoscope tip. However, fiber-optic image guides have largely been replaced by copper wire that transmits digital information, from a CCD at the endoscope tip to a video processor for display. A variety of endoscope models from several manufacturers are commercially available. Procedure-specific endoscopes are designed to enhance endoscopic diagnosis and therapy.

Endoscope design   

Flexible endoscopes are composed of three sections: the control section, the insertion tube, and the connector section (Fig. 1). Particular features of any given endoscope are modified to best accomplish the intended use. Endoscopes developed for specific procedures may be used for other applications as clinically indicated (e.g. a thin caliber colonoscope may be used for small bowel enteroscopy) [5]. While there are variations among endoscope manufacturers, there is general uniformity to endoscope design. Endoscope specifications do vary in any given category of endoscope (e.g. colonoscope vs. duodenoscope). Variables include insertion tube length, diameter, and stiffness; instrument channel size and number; and configuration of the distal end of the insertion tube. The control section is modified for specific purposes such as a second instrument channel or an elevator lever control for the duodenoscope. These features affect the endoscope's ergonomics, depth of insertion, and the accessories that can be used adjunctively.

Control section   

The control section is held in the operator's left hand (Fig. 1). It has two stacked angulation control knobs which direct up/down and left/right deflection of the endoscope tip. These control knobs can be locked in position. Specialty small caliber endoscopes such as the choledochoscope have only one knob, limited to up/down deflection capability. There are air/water and suction valves on the upper front portion of the control section. There are remote switches to modify or capture the video image. The entry port to the instrument channel(s) is (are) located on the lower front portion of the control section. Fiber optic instruments have an eyepiece located at the top of the control section for direct image viewing. Specialty components may include such things as variable stiffness and video magnification controls.

Insertion tube   

The insertion tube is attached to the control section, and is the portion of the endoscope that is inserted into the patient (Fig. 2). The length, diameter, and degree of stiffness of the insertion tube vary among models. The insertion tube contains one or two instrument channel(s), one or two light guide bundles (incoherent fiber optic), an air channel, a water channel, either an image guide bundle (coherent fiber optic) or a CCD chip with wire connections, and angulation wires. The angulation wires deflect the bending section of the insertion tube. Maximum deflection is 180–230°[6].

The endoscope tip contains (1) an opening(s) to the accessories/suction channel; (2) an air/water nozzle for air insufflation, positioned to wash the lens of debris; (3) light guide illumination system; (4) objective lens system. Instrument models are designed with forward-, side-, or oblique-viewing optics. Insertion tube lengths range from 63 to 2800 cm, with diameters ranging from 2.8 to 13.7 mm. Instrument channel diameters vary from 0.75 to 4.8 mm. Dedicated ERCP and EUS scopes have use-specific modifications at the distal tip.

Connector section   

The connector section of the endoscope has a light guide, an air-pipe, and electrical contacts compatible with the processor/light source. This section also has side connectors for a water container, suction, CO₂, insertion tube venting, and an S (safety)-cord connecting mount, which grounds the endoscope, reducing the electrical shock hazard to the operator. Some models include a separate lavage port.

Imaging   

Endoscopic imaging is achieved through either fiber optic or electronic (video) systems. Fiber optic endoscopes utilize a coherent bundle of glass fibers to transmit an image from the tip of the endoscope to the eyepiece. Some specialty endoscopes are only available in a fiber optic format. A video-adaptor or add-on camera can be used to convert a fiber optic image to video format. Video-endoscopes have a black and white solid state image sensor called a CCD mounted at the tip of endoscope that allows an image to be transmitted via an electronic signal to a video processor for display on one or more video monitors. This signal is converted to a color image by one of two systems.

• Color CCD has a multicolor mosaic filter affixed to the surface of the CCD with illumination by a steady white light.
  
• RGB sequential imaging has a rotating multicolor wheel filter (red-green-blue) located between the light source and the light guide, yielding a visual strobe effect. The standard magnification is 7× with a 20-inch monitor. Specialty endoscopes offer image magnification capabilities (70×–150×) [7]. Endoscope imaging is detailed in the following chapter (Aabakken).
  

Light source/processors   

The fiber optic light source is a relatively simple component with or without an air/water pump. High-intensity light bulbs (e.g. halogen) are commonly used as fiber optic light sources. The front panel is equipped with controls and a receptacle for the connector section.

The video-endoscope processor is more complex and expensive than the fiber optic light source as it contains all the circuitry to process the video signal. Some model designs have separate video processors and light source/air–water pump components, while others have combined the components into one chassis. The front panel of a video processor allows for image adjustment, air/water pump control, and a receptacle for the endoscope connector section. A variety of illumination bulb types are used in video processors, including xenon, halogen, and metal halide.

Endoscope equipment compatibility   

Fiber optic endoscope equipment from various manufacturers and generations may be compatible and used interchangeably with specially designed adaptors. Compatibility and interchangeability are less feasible with video-endoscopy. The video processor has to be compatible with the endoscope attached to it. For example an RGB sequential endoscope is not compatible with a processor designed for a color chip endoscope. Also, within the same optical family or manufacturer, endoscope generations may or may not be compatible with video processors from newer or older generations. Finally, even when the same color system is used, video-endoscopes are not compatible with video processors from different manufacturers.

Endoscope categories   

Esophagogastroduodenoscope (gastroscope)   

The esophagogastroduodenoscope or gastroscope is a forward-viewing instrument used primarily for evaluating the esophagus, stomach, and duodenum. Standard feature variables include insertion tube diameter (5.1–12.8 mm), working length (925–1100 mm), and instrument channel size (2.0–6.0 mm) and number (1–2). Specialty features may also include oblique viewing, ultra thin design, and video zoom capability. List prices range from $13 700 to $24 900.

Enteroscope   

The enteroscope is similar in design to the gastroscope but is fashioned with a longer insertion tube, allowing for deep intubation of the duodenum and proximal jejunum. Standard feature variables include insertion tube diameter (5.0–11.7 mm), working length (2180–800 mm), and instrument channel size (1.0–3.5 mm). An over-tube may be used to retard gastric looping and enhance insertion depth [5,8]. List prices range from $23 800 to $33 275.

Duodenoscope   

The duodenoscope is a side-viewing (90° to the longitudinal access of the insertion tube) instrument designed primarily for ERCP (Fig. 3). Duodenoscopes are equipped with an elevator lever that enhances fine movement of devices passed through the endoscope accessory channel. The elevator lever is positioned at the opening of the accessory channel and is maneuvered by a cable operated from the control section. Standard feature variables include insertion tube length (1030–250 mm), insertion tube diameter (7.4–12.6 mm), and channel size (2.0–4.8 mm). Larger channel instruments allow the passage of larger diameter accessories and even a choledochoscope (see below). List prices range from $19 400 to $30 100.

Choledochoscope   

A choledochoscope is a thin caliber endoscope that is passed through the instrument channel of a duodenoscope and inserted intraductally for direct imaging of the biliary and pancreatic ducts (Fig. 4a,&b). Standard feature variables include insertion tube length (1870–900 mm), insertion tube diameter (2.8–3.4 mm), and instrument channel size (0.75– 1.2 mm).

Choledochoscopes are commercially available only in fiber optic format at the time of this writing; however, video choledochoscopes and pancreaticoscopes are under development and have been evaluated as prototypes. List prices range from $18 900 to $22 700. The fragility of these instruments has limited their commercial viability [9].

Echoendoscopes   

The echoendoscope is a hybrid instrument that combines flexible endoscopy with high-resolution ultrasound imaging. Ultrasound imaging elements are affixed to the tip of modified endoscopes to allow close proximity ultrasound imaging of the luminal digestive tract and adjacent organs. Standard feature variables include insertion tube length (975–1325 mm), insertion tube diameter (7.9–13.7 mm), instrument channel size (2.2–3.7 mm), and orientation of the optical (forward or oblique) and ultrasound (longitudinal or radial) images. Radial scanning echoendoscopes have a sector scanning ultrasound transducer affixed to the tip of the endoscope providing 270–°360° imaging (Fig. 5).

Longitudinal imaging is acquired via linear-arrayed piezoelectric ultrasound transducers. The linear array format allows for ultrasound-guided fine-needle biopsy tissue sampling (Fig. 6)[10]. List prices range from $33 800 to $71 500. Catheter ultrasound probes, both radial scanning and linear array, are commercially available. These high-frequency devices may be passed through the accessory channel of the endoscope for high-resolution imaging, albeit with limited depth of penetration.

Colonoscope   

The colonoscope is a forward-viewing instrument designed to evaluate the entire colon and the distal terminal ileum. Standard feature variables include insertion tube length (1330–700 mm), insertion tube diameter (11.1–13.7 mm), instrument channel size (2.8–4.2 mm), and number (1–2). List prices range from $11 500 to $25 750. One manufacturer has developed a modification of the standard colonoscope incorporating a control capable of varying the stiffness of the distal portion of the insertion tube [11].

Sigmoidoscope   

The sigmoidoscope is a forward-viewing instrument (a shorter version of a colonoscope) used to evaluate the rectum and sigmoid colon. The flexible sigmoidoscope was developed for screening average risk patients for colorectal polyps. Standard feature variables include insertion tube length (630–790 mm), insertion tube diameter (12.2–13.3 mm), and instrument channel size (3.2–4.2 mm). List prices range from $5250 to $15 100. A disposable, sheathed sigmoidoscope is also commercially available [12].

Wireless capsule endoscopy   

The wireless endoscopy system has three components: a capsule 'endoscope', an external receiving antenna with attached portable hard drive, and a personal computer workstation for review and interpretation of images [13]. The capsule endoscope is a disposable plastic capsule (Fig. 7) which weighs 3.7 g and measures 11 mm in diameter × 26 mm in length. The contents include a metal oxide silicon (CMOS) chip camera, a short focal length lens, four white light-emitting diode (LED) illumination sources, two silver oxide batteries, and a UHF band radio telemetry transmitter.

The capsule is activated after removal from a magnetic holder. The wireless capsule endoscope provides image accrual and transmission at a frequency of two frames per second until the battery expires after 7 (± 1) h. The capsule is passively propelled through the intestine by peristalsis. The patient wears a shoulder-supported belt pack holding a power supply containing five ('D cell'-sized) nickel-metal 1.2 V batteries, and a small 305 GB hard drive for archiving received images. Data are downloaded from the belt pack recorder to a customized PC workstation. Images are then reviewed at an adjustable rapid scan mode that can display between 1 and 25 frames per second. Interpretation requires 30–120 min. An anticipated software enhancement is intended to provide automated screening for potentially significant findings based on algorithms for image assessment.

 Gastrointestinal endoscopic accessories   

Endoscopic accessories are used for tissue sampling, ablation, marking, and resection; object retrieval; image enhancement; injection; hemostasis; enteral access; dilation; and stenting. This section provides an overview of accessory devices used in endoscopy. Specific applications of these accessories are detailed in their respective sections.

Tissue sampling   

Tissue sampling is used to acquire specimens for histological and cytological inspection. Tissue sampling may be directed or random. The principles of tissue sampling and devices used are fairly uniform throughout the digestive tract. Tissue sampling can be performed with forceps biopsy, brush cytology, fine-needle aspiration, and snare resection. Snare resection will be covered elsewhere, with polypectomy.

Biopsy forceps   

Biopsy forceps are used to sample mucosa and mucosal-based lesions. Endoscopic biopsy forceps consist of a flexible, metal-coil outer sheath that houses a steel cable connecting a two-piece plastic handle to opposed metal biopsy cups. Some biopsy forceps sheaths are coated with a synthetic polymer to improve passage through the endoscope accessory channel.

Single-bite cold-biopsy forceps   

Single-bite cold-biopsy forceps allow sampling of only a single specimen at a time. Double-bite cold-biopsy forceps (most commonly employed) are equipped with a needle-spike between the opposing biopsy cups (Fig. 8). The needle-spike serves several purposes. First, the spike can be used to impale the tissue of interest, thus stabilizing the forceps cups for selected tissue sampling. Second, needle version forceps obtain deeper biopsies than non-needle versions [14]. Lastly, the spike secures the first specimen on the device while a second specimen is obtained. Without the spike, attempts at multiple tissue sampling with single-bite forceps may result in the loss of specimens and crush artifact.

Biopsy cup jaws   

Biopsy cup jaws may be standard oval or elongated, fenestrated or non-fenestrated, and smooth or serrated. Large-capacity cup, or 'jumbo' biopsy, forceps obtain a larger volume of tissue than standard capacity forceps, but may require a large channel endoscope for their use. Large-capacity biopsy forceps require a biopsy channel of at least 3.6 mm and yield 2–3× the surface area, but not generally deeper specimens. The use of jumbo biopsy forceps has been advocated by some for surveillance in Barrett's esophagus and for excisional biopsy polypectomy of diminutive colonic polyps [15].

Multi-bite forceps   

Multi-bite forceps have been developed that can obtain four or more specimens on a single pass. In a prospective, partially blinded, randomized trial of multi-bite forceps vs. conventional forceps, the multi-bite forceps compared equivalently for diagnostic quality [16]. The multi-bite forceps have the potential to save time when a large number of specimens must be obtained, such as in surveillance of patients with ulcerative colitis.

Other specialty forceps   

Other specialty forceps include a variety of innovations for challenging circumstances.''Swing-jaw' forceps feature a rocking cup assembly action intended to direct the jaws of the forceps toward the tissue of interest. 'Rotatable' forceps are designed to do just that, with variable degrees of control. 'Angled' forceps assume a 90° orientation to the long access of the scope once extended from the accessory channel.

Monopolar hot biopsy forceps   

Monopolar hot biopsy forceps were developed for simultaneous tissue biopsy and coagulation. Thermal energy is generated when current, passed through an insulated shaft, is introduced to the tissue at the blunted edges of the forceps jaws [17]. Heat energy is regulated and determined by generator voltage and waveform, current density, and application time [18]. Bipolar hot biopsy forceps have also been developed. Bipolar forceps have insulated biopsy cups except for the cup edges, which are the electrodes [18]. Tissue injury is deeper with monopolar hot biopsy forceps than with bipolar forceps [17].

Hot biopsy became popular for biopsy resection of diminutive colonic polyps. The rationale for coagulative tissue sampling is to destroy neoplastic tissue, thereby preventing residual or recurrent adenoma and the development of carcinoma. However, there is insufficient data to indicate that excisional hot biopsy forceps removal reduces the incidence of colorectal cancer or even complete eradication of all neoplastic tissue [17,19,20]. Furthermore, complications of hot biopsy forceps include hemorrhage, perforation, and postcoagulation (trans-mural burn) syndrome [17]. Based on these observations, routine application of hot biopsy is not recommended.

Reusable vs. disposable biopsy   

The relative virtues of reusable vs. disposable biopsy forceps can be debated. Arguments focus on cost, operational performance, and infection control. In two prospective, randomized, pathologist-blinded trials, there were no perceived differences in quality of specimen for histological diagnosis between a variety of commercially available reusable and disposable biopsy forceps [21,22].

Yang et al. prospectively measured cost and operational performance of disposable and reusable forceps in 200 biopsy sessions [23]. Reusable costs factored in acquisition and reprocessing. They found that malfunction of reusable forceps increased with number of uses. At up to 15–20 uses, reusable and disposable forceps costs are similar, when the cost of disposable forceps is around $40.00. When reusable forceps can be used more than 20 times, they are less expensive.

However, in their study the performance of reusable forceps deteriorated significantly in this range. Deprez et al., in a much larger study (7740 sessions) using similar design and the lowest available purchase price for disposable forceps at the time ($26.90), reported that total purchase and reprocessing costs for reusable forceps were 25% of those of disposable devices [24]. Further, an average of 315 biopsy sessions were performed with a reusable forceps, extending their mean life to 3 years.

Conversely, in a third study, disposable forceps outperformed their reusable counterparts and offered a cost advantage [25]. These authors also reported a concern over residual proteinacious material observed in reusable forceps, raising an infection control risk. This charge was countered, however, in a study by Kozarek et al. who performed an ex vivo evaluation of cleaning, and an in vivo evaluation of function, performance, and durability of reusable forceps [26]. Their analysis concluded that reusable biopsy forceps are confidently sterilized when accepted cleaning and sterilization protocols are followed. Sterilized reusable biopsy forceps were used a mean 91 times, rendering the potential for significant cost saving, again, depending on acquisition and reprocessing costs. All published cases of transmission of infection associated with reusable biopsy forceps have been attributed to breaches in accepted standards of device reprocessing [27].

The functional performance of reusable biopsy forceps will ultimately deteriorate with increased number of uses. The durability can be extended with care in use and reprocessing. Cost comparisons depend mainly on the cost of disposable devices. Users should also factor in the cost of medical waste disposal and environmental impact associated with disposal of single use devices.

Cytology brushes   

A variety of commercially available cytology brushes are used for tissue sampling, especially in the esophagus and pancreatico-biliary ductal systems. Designs include variable brush sizes and stiffness, wire guided and non-wire guided, single and multilumen, and with or without a flexible guide tip. Outer sheaths for brushes used in ERCP are 6–8 Fr [28,29]. A cytology balloon for non-endoscopic esophageal cytological screening and surveillance for infectious and neoplastic diseases has been described [30].

Needle aspiration   

Hollow bore needles may be used for aspiration cytological tissue sampling. ERCP aspiration needles consist of a retractable 7.5 mm 22 gauge needle attached to a ball-tipped catheter [31]. The needle is advanced into the target tissue under fluoroscopy and aspiration is applied. Howell et al. developed a technique for sampling biliary stricture by endoscopic FNA [32]. Needle aspiration of submucosal lesions under direct endoscopic guidance can be performed; however, this technique and the devices to support it are currently undergoing refinement [33]. EUS-guided fine-needle aspiration is covered in the Endoscopic Ultrasound section.

Polypectomy snares   

Polypectomy snares are used for resection of sessile and pedunculated epithelial lesions throughout the digestive tract (Fig. 9). Snares are used in standard and advanced (often considered under the rubric of endoscopic mucosal resection ([EMR)]) polypectomy techniques. Polypectomy snares are available in a variety of shapes, sizes, and materials. Specialty snares are designed with special features for specific performance properties.

Snares may be designed and marketed as disposable or reusable. Reusable snares must be designed so they may be disassembled for cleaning and sterilization and then reassembled, plus have properties that enable them to retain their configuration and performance through multiple use and cleaning cycles. These constraints, plus the availability of cheap materials and production costs, have promoted broad acceptance of disposable snares for endoscopic polypectomy.

Polypectomy snares consist of an attached or continuous wire loop housed within a flexible synthetic polymer sheath. This portion of the device is passed through the accessory channel of the endoscope. Sheaths are typically 7.0 Fr in diameter, for a minimal channel size of 2.8 mm, and up to 230 cm or more in length. The wire and sheath are affixed to a moving-parts plastic handle at the operator end of the device. The handle controls opening (extension) and closing (retraction) of the wire loop from and within the outer sheath. The snare wire couples to an electrical connector within the handle. The handle has a receptacle for connection to an active cord, thus allowing completion of an electrosurgical circuit.

While bipolar snares have been developed, most snares employ monopolar current. Bipolar snares are designed with each half of the snare loop functioning as an electrode such that current flows across the polyp [34]. In monopolar snares the current flows from the snare to a distant return electrode (grounding pad), generating local thermal energy for cutting and coagulation [18]. There are no comparative trials of bipolar vs. monopolar snares.

Braided stainless steel wire is the most commonly used material for polypectomy snares, owing to its strength, conduction properties, and configurational memory. The snare wire typically is 0.30 - 0.47 mm in diameter. Nitinol wire snares may have superior configurational memory but lack sufficient stiffness, tending to leave them floppier than desired. Monofilament wire snares promote transection over coagulation and are largely limited to use in cold-snare polypectomy of small polyps in patients without coagulation disorders [35].

The standard shape of the snare loop is oval or elliptical. Alternative configurations include round, crescent, or hexagonal. A variety of snares are available through device manufacturers and can be viewed in their product catalogues. Selection of snare configuration is based on personal preference. Experienced endoscopists may choose specific snare shapes for removal of individual lesions based on the lesion's location, orientation, size, and configuration. The standard size and shape snare suffices for the vast majority of instances. There are no comparisons of snare shapes to support superiority of one or more snare configurations over others.

While there is some variability among the manufacturers, standard size snare loops are typically 2.0– –2.5 cm in diameter. Loop lengths vary based on configuration and manufacturer. Mini-snares have loop diameters of 1.0 –1.5 cm, and are handy for completion resection of residual adenoma following mucosectomy of a sessile lesion and for resection of diminutive polyps [36]. Jumbo snares have loop dimensions of up to 3  × 6 cm and are used to transect large pedunculated polyps not accommodated by standard snares.

Other specialty snares have been developed to enhance success when circumstances prove challenging to characteristics of ordinary snares. While specialty snares may offer advantages in specific instances, most experienced endoscopists do quite well with standard-loop snares along with the occasional use of mini- and jumbo snares. Nonetheless a familiarity with, and limited stock of, specialty snares may ensure success when faced with the occasional defiant polyp. Duck-bill® and multiangled (Wilson-Cook Medical Inc., Winston-Salem, NC) snares are intended for lesions difficult to access based on their wall location with respect to the tip of the colonoscope. Rotatable snares can be adjusted so that the snare loop opens in an orientation favorable to polyp entrapment.

Needle- or anchor-tipped snares have a short, pointed barb at the tip of the snare. The modified tip is intended to aid in stabilizing the snare for polyp capture. By impaling the barbed tip into the bowel wall just beyond the lesion, the snare tip can be fixed in place while the loop is being flexed to open over and around the polyp.

A variety of snares have been developed and marketed for removal of sessile polyps. These iterations include barbed, spiral, and 'hairy' snares. Each is designed to grip the edges of low profile sessile lesions. There are no studies to indicate superiority of modified over standard snares for resection of sessile colon polyps.

Retrieval devices   

An assortment of retrieval devices has been developed for extraction of resected specimens and foreign objects from the luminal digestive tract. These include a variety of graspers, baskets, and nets [37]. Specimen retrieval is critical for histopathological interpretation. The Roth net (US Endoscopy, Mentor, OH) enables the secure retrieval of multiple specimens, thereby reducing the need for repeated withdrawal and reinsertion of the endoscope (Fig. 10). The secure handling of the specimen makes this device ideal for retrieval of specimens from the upper digestive tract, wherein unintentional dislodgement in the airway must be avoided.

Many tissue sampling and retrieval devices may be applied to the management of ingested foreign objects. These include: retrieval net, grasping forceps ('Alligator' or 'Rat-tooth'), three-pronged grasper, Dormia basket, polypectomy snare, variceal band-ligation hood, and protector hood [38]. Over-tubes of both standard length that bypass the upper esophageal sphincter and longer 45–60 cm tubes that extend into the stomach should be available. Over-tubes can protect the esophageal mucosa when retrieving sharp objects, allow multiple passes of the endoscope, and protect the airway during retrieval.

Alternatively, a latex protector hood that can be attached to the end of the endoscope can protect the airway and the mucosa when an object is grasped and pulled tightly against the scope during withdrawal. Knowledge of the type of object and its location prior to endoscopy may permit an ex vivo or practice 'dry run'," allowing proper equipment selection and improved outcome [39].

Injection devices   

Injection devices include injection needles, spray catheters, and ERCP catheters.

Injection needles   

Injection needles are devices passed through the accessory channel of the endoscope to enable injection of a solution into tissue. Injection needles are used for injection-assisted polypectomy, hemostasis (variceal, non-variceal, and hemorrhoidal), and tattooing.

Injection needles consist of an outer sheath (plastic, Teflon, or stainless steel coil) and an inner hollow core needle (21–25G) (Fig. 11)[40]. The needle tip is typically beveled. Needle tip length should be sufficient to routinely penetrate into the submucosa and not so long as to routinely penetrate through the colon serosa. They are available in colonoscopic lengths and typically have an outside diameter 2.3–2.8 mm. A metal and plastic luer lock handle controls needle extension and retraction to fixed or variable lengths. Some versions allow the needle to be preferentially locked when in the extended position. Most commercially available injection needles are single-use disposable.

Metal coil-sheathed needles may offer advantages over their plastic-sheathed counterparts in that they are less likely to kink and are more apt to remain fully functional when articulated. This allows use even when there is excessive looping of the colonoscope or when operating with a retroflexed colonoscope position. Metal coil sheaths are also less likely to allow unintended needle puncture through the sheath with the associated risk of scope injury. However, there are no published trials comparing various injection catheters for colonoscopic applications.

An injection needle has also been incorporated into a multipolar electrocautery device. This device allows combination injection and contact-thermal hemostatic therapy for non-variceal bleeding.

Spray catheters   

Spray catheters are used when performing chromoendoscopy. Chromoendoscopy employs a chromic agent to enhance the detection or discrimination of dysplastic epithelia [41]. Chromic agents may be vital stains or contrast agents. Vital stains are selectively taken up by epithelial cell cytoplasm, whereas contrast agents coat the epithelial surface enhancing the contour relief pattern. Contrast agents are commonly employed when performing high-resolution and high-magnification endoscopy [41].

Spray catheters are disposable, flexible, hollow plastic sheaths, with a plastic luer lock handle, and a metal spray nozzle tip (Fig. 12). Alternatives to dedicated spray catheters are injection needles, ERCP catheters, and simple injection through the accessory port itself. Spray catheters generally allow the most controlled, precise, and tidy application for chromoendoscopy.

ERCP catheters   

A plethora of specially designed catheters are commercially available for cannulation and injection of contrast into the pancreatico-biliary systems. These are single, double, or triple lumen plastic catheters that are passed through the accessory channel of the duodenoscope. In addition to facilitating radiocontrast dye injection, the catheter lumina accept guidewires for access and device exchange. Specialty devices are equipped with adjunctive apparatti to perform specific actions. Sphincterotomes have an electrosurgical wire for transecting the papillary sphincters. Stone retrieval balloon and pneumatic dilating catheters have inflatable balloons specific to their intended purposes. The array of ERCP devices can be further interrogated in the ERCP section.

Hemostatic and ablation devices   

Contact and non-contact thermal devices   

Thermal devices are used for coagulative hemostasis and ablation. Contact thermal devices include the heater probe and multipolar electrocautery (MPEC) probes [42]. Non-contact thermal devices include laser fibers and argon plasma beam coagulators [42].

Heater probe   

The heater probe (Olympus America, Melville, NY) consists of a Teflon-coated hollow aluminum cylinder with an inner-heating coil at the tip of a flexible shaft. A thermocoupling device at the tip of the probe allows maintenance of a predetermined and constant temperature once the pulse has been initiated for a predetermined duration of activation. The mechanism of tissue coagulation is heat transfer. Water for irrigation and cleansing the target tissue passes through a central port. A foot pedal controls coagulation and irrigation. MPEC probes deliver thermal energy by completion of an electrical circuit between two or more electrodes on a probe at the tip of a flexible shaft [43]. The electrodes may be arrayed linearly or in a spiral fashion (Fig. 13).

The circuit is completed locally and ceases with loss of conductivity as tissue desiccates, limiting maximum temperature (100 °C) and depth and breadth of tissue injury. There is a central port for irrigation of water. Foot pedal control is standard. A variety of MPEC probes in colonoscopic lengths are available from endoscope device manufacturers with similar specifications but varied characteristics. One device combines an injection needle with the MPEC probe. Both the heater and MPEC probes can be used tangentially and en face.

Laser fibers   

Laser fibers transmit collimated, highly energized light energy, emitting a focused monochromatic beam [44]. They are flexible glass fibers with coated shafts. The laser light delivered from a focal distance of ~10 mm from the tissue results in coagulation or vaporization. Cylindrical diffuser laser fibers are used in photodynamic therapy (PDT) (Fig. 14a).

These flexible glass fibers are modified with a variable length tip that promotes uniform scattering of laser light energy circumferentially along the long axis of the diffuser tip. PDT utilizes non-thermal laser energy to interact with a photosensitizing agent present in target tissue. A further modification of the cylindrical diffusion catheter used for PDT in the esophagus incorporates an inflatable centering balloon (Fig. 14b).

Argon plasma beam coagulator   

The argon plasma beam coagulator is a non-contact electrocoagulation device [45]. Monopolar current is conducted to the target tissue through an ionized argon gas (argon plasma) (Fig. 15). As it is monopolar current, a grounding pad is required to complete the circuit. Electrical energy flows through the plasma from the probe tip to the target tissue. Coagulation occurs at the plasma–tissue surface interface. As the target tissue desiccates, the plasma stream shifts to adjacent, non-desiccated tissue. The probes consist of a flexible Teflon tube as a shaft, with a tungsten electrode contained in a ceramic nozzle at its distal tip [46].

The operative distance of the probe from the target tissue is 2–8 mm. While mode-specific probes are available, the arch of energized argon plasma to the tissue enables en face or tangential coagulation/ablation with the standard probe. An argon plasma beam coagulation unit (ERBE USA, Marietta, GA; ConMed Electrosurgery, Englewood, CO) includes a high-frequency electrosurgical generator, source of argon gas, gas flow meter, flexible delivery catheter, grounding pad, and foot switch to activate both gas and energy.

Contact and non-contact thermal devices are used for hemostasis of bleeding from ulcers, postpolypectomy, angiodysplasia, and diverticulosis. Contact and non-contact thermal devices are also used to ablate residual adenomatous-appearing mucosa at the margins of snare resection of sessile polyps and for ablation of lesions unamenable to endoscopic or surgical resection [47–49]. Non-contact thermal devices have been used to ablate obstructing cancers to achieve recannulation of the lumen, and for hemostasis of inoperable cancers.

Mechanical hemostatic devices   

Mechanical hemostatic devices include bands, clips, and detachable loops.

Band ligation   

Band ligation devices consist of a transparent, hollow-chamber, friction-fit adapter affixed to the tip of the endoscope, preloaded elastic band(s), and a release mechanism. The target tissue is suctioned into the hollow chamber of the friction-fit adapter (Fig. 16). A trigger mechanism deploys an elastic band, ligating the target tissue. Tissue ligation results in hemostasis with subsequent necrosis and sloughing [50,51]. Single and multiple band ligators are available. Variceal band ligation is effective in the control of active hemorrhage in 86–91% of cases [52,53].

Subsequent sessions result in eradication of esophageal varices and decreased rebleeding. Band ligating devices have been used for non-esophageal varices, including gastric, intestinal, and colonic varices, but data are limited. Case reports and small series have described the use of endoscopic band ligation for treatment of bleeding angiectasias, Mallory–Weiss tears, polypectomy sites, Dieulafoy lesions, and duodenal ulcers. Multi-band ligators, all with transparent outer cylinders, carrying 3, 4, 5, 6, or 10 bands, are now available.

There are three commercially available devices on the market: Saeed Multi-Band Ligators (Wilson-Cook Medical, Inc., Winston-Salem, NC)), Speedband Multiple Band Ligator (Microvasive, Boston Scientific Corp., Natick, MA), and a new system from Bard (CR Bard, Inc., Billerica, MA). All of these devices have easy to assemble components and vary only slightly in their form and function.

Metallic clip application via flexible endoscopes   

Metallic clip application via flexible endoscopes has had considerable appeal for a variety of indications. The most evolved experience has been with the HX series of endoscopic clip fixing devices (Olympus Corp., Tokyo, Japan). This device was first conceived for hemostasis of non-variceal bleeding sources. Another commercially available clipping device is the Triclip (Wilson-Cook Medical, Inc., Winston-Salem, NC).

Endoscopic clip application has been used effectively for hemostasis of immediate and delayed bleeding from polypectomy and hot biopsy forceps sites; diverticular, arteriovenous malformations, and variceal bleeding; and prophylaxis of postpolypectomy bleeding pre- and post snare resection. Such mechanical hemostasis allows localized, directed, and specific therapy, while minimizing tissue injury at the treatment site.

Other applications have included lesion marking (bleeding or tumor site), fixation of endoscopically placed decompression tubes, and primary closure of resection sites and perforations. The clip-fixing device has evolved from its first inception to a relatively easy to use, reliable, and now rotatable delivery device (Fig. 17)[54,55].

A single use, preloaded iteration has become available. The clips themselves are configured of a multiangled stainless steel ribbon. Clips are available in a limited variety of lengths and configurations. Clips typically slough off in 3–4 weeks and pass uneventfully in the stool.

In practice, the clip is loaded onto the hooking cable and withdrawn into the outer plastic tube sheath. This procedure is unnecessary when using the preloaded ready-to-use versions. The delivery device insertion tube is then passed through the endoscope working channel. With the target lesion in view, deployment is initiated by exposing the clip from within the tube sheath. Withdrawing the cable within the tube sheath slides the pipe clip up the clip itself, fully opening the clip. With the rotatable version, a rotator-disc located on the control section may be used to turn the clip to the desired orientation. The insertion tube is then advanced so the teeth of the clip engage the target tissue, whereupon further sliding of the pipe clip closes the clip and completes deployment, detaching the clip from the clip connector.

Becoming facile with loading and deployment of endoscopic clips requires practice and regular use. Clips deploy with equal reliability in the en face, as well as in retroflexed scope positions. Some models are equipped with the rotating wheel that works surprisingly well. The clip can be rotated to the desired orientation the majority of times. The rotator feature and improved durability are clear advantages over earlier clip designs. An unlimited number of clips can be placed during a single session. Mechanical cleaning followed by gas sterilization can reprocess the reusable-model delivery device.

Endoscopic mucosal clips are highly effective for prophylactic hemostasis of polypectomy and mucosectomy sites and for primary or secondary hemostasis of postpolypectomy bleeding [56,57]. Endoscopic hemoclips promote durable hemostasis and do not incur additive tissue injury as is the case with thermal or injection techniques. Among 72 cases of colonoscopic immediate postpolypectomy (n = 45), delayed postpolypectomy (n = 18), and postbiopsy (n = 9) bleeding, effective and durable clip hemostasis was achieved in all but one case [58]. There were no episodes of recurrent bleeding or need for surgery related to bleeding.

Marking with clips   

Marking with clips is effective for lesions benefiting from precise localization preoperatively, including tumors and bleeding sites (e.g. diverticulum). Clips can readily be palpated or located with fluoroscopy at the time of surgery. Clips may be used for the fixation of colonic decompression tubes to prevent tube migration. Lastly, endoscopic mucosal clips have been used to achieve transient tissue remodeling to oppose surrounding tissue at a resection site or luminal defect [59]. The latter application should be limited to use in highly selected instances.

Detachable loops   

Detachable loops have been developed for the prevention and management of bleeding from polypectomy sites. Such bleeding is reported to occur in 2% of all polypectomies. Bleeding occurs more frequently with the removal of large polyps with thick stalks and in patients who have underlying coagulopathies or those taking anticoagulation therapy or non-steroidal anti-inflammatory drugs. The detachable loop snare ligature was developed for primary or secondary prophylactic therapy for postpolypectomy bleeding, or as primary or secondary treatment of active or recent postpolypectomy hemorrhage [60–63].

The detachable snare or '"endoloop'" (Olympus HX-20Q, Olympus Corp., Tokyo) is composed of an operating apparatus (MH-489) and an attachable loop of nylon thread (MH-477) (Fig. 18). The operating apparatus consists of a Teflon sheath 2.5 mm in diameter and 1950 mm in working length, a stainless steel coil sheath 1.9 mm in diameter, a hook wire, and the handle. The nylon loop is non-conductive and consists of a heat-treated circular or elliptically shaped nylon thread and a silicon-rubber stopper that maintains the tightness of the loop.

The optimal application of this device for prevention and management of polypectomy bleeding is yet to be determined. When used for primary prophylaxis, the flexibility of the loop makes it difficult to encircle the large polyps, wherein its use would be most desirable. Entanglement of the subsequent electrocautery snare with the previously placed nylon loop may be a source of frustration. Unintentional transection of the polyp stalk with the detachable loop snare, resulting in a frank hemorrhage, is a risk in the hand of an inexperienced assistant. When used as secondary prophylaxis against postpolypectomy bleeding, the loop is placed over the residual pedicle immediately postpolypectomy. This, too, can be challenging in all but the most prominent of residual stalks.

Matsushita et al. summarized their experience. They reported primary prophylactic use of a detachable snare for colonoscopic polypectomy of 20 large polyps in 18 patients and secondary prophylactic placement following conventional polypectomy of five polyps in five patients [64]. Four of the 20 polyps were semipedunculated and the loop slipped off after polypectomy in 3 of the 4. Among the 16 pedunculated polyps, bleeding occurred in 4 cases because of transection by the loop of the stalk before polypectomy in one, slipping-off of the loop in one, and insufficient tightening of the loop in two.

Among the five patients in whom the loop placement was attempted following conventional polypectomy, the residual stalk could not be ligated in three of the five lesions because of flattening. These authors concluded that the detachable snare is difficult to apply and subject to operator-dependent error. For the treatment of active bleeding from a polypectomy site again the loop was only effective when there was a sufficient pedicle to allow ensnarement. Iishi et al. report a more favorable experience [65].

Primary loop ligation for treatment of postpolypectomy hemorrhage is most apt to occur in the immediate postpolypectomy setting before the stalk has had a chance to flatten. In most instances when postpolypectomy hemorrhage is delayed, there is active hemorrhage or adherent clot obscuring view. Initial attempts at hemostasis with injection of epinephrine or alcohol solution may achieve partial hemostasis and improve visualization. If a sufficient residual stalk is present, loops may well be applied; however, alternatives include additional electrocautery, placement of endoscopic hemostatic clips, or even the placement of a variceal rubber band ligator.

Transparent cap   

Plastic transparent caps that affix to and overhang the tip of the endoscope may be used to enhance colonic visualization and to facilitate EMR [66]. These caps are modifications of devices initially used for endoscopic band ligation therapy. The caps consist of a hollow cylinder of fixed or flexible plastic and a snug-fitting adaptor that slides over and is affixed to the tip of the endoscope (Fig. 19)[67]. Those devised for cap-assisted EMR may have a built-in rim to house a predeployed, specially designed snare. A commonly used cap size is 16 mm in outer diameter with 2 mm wall thickness, and 15 mm in length. However, they are available in a variety of sizes and configurations, including straight or oblique-angled opening, depending on the intended purpose and endoscope being used (Olympus America Inc., Melville, NY).

For cap-assisted EMR, submucosal injection of saline or other sterile solution is performed to 'lift' the mucosal-based lesion on a submucosal cushion. The scope tip with the attached cap is then placed over the lesion. By applying suction, the cap cylinder becomes a vacuum chamber, drawing the target tissue into a pseudo-polyp within. The predeployed snare is then closed and standard electrocautery excision is performed. This technique has been described for lesions throughout the digestive tract and is safe and effective in experienced hands [68]. Cap-assisted EMR may also be used for completion resection of flat or sessile lesions not amenable to other mucosectomy techniques [69].

The transparent cap may also be used to enhance mucosal imaging during colonoscope withdrawal. Using this technique, the semilunar folds can be flattened out for improved inspection. In two series, use of the cap did not interfere with colonoscope insertion or terminal ileal intubation, and enabled identification of small polyps not seen on standard colonoscopy [70,71]. Caps are also used in some applications of magnification endoscopy.

Dilation devices   

Dilatation of strictures is indicated when there is functional impairment or a need to access beyond the stricture for diagnosis or therapy. A variety of devices are available for dilation of digestive tract strictures. Many dilators have indication-specific characteristics; others are relatively generic in design.

Dilation devices can be organized into two categories: fixed-diameter push-type dilators and radial expanding balloon dilators. Fixed-–diameter push-type dilators exert axial as well as radial forces as they are advanced through a stenosis [72]. Balloon dilators exert radial forces when expanded within a stenosis.

Dilators can be delivered to strictures in a number of ways based on the dilator design and operator technique, including with or without endoscopic, fluoroscopic, and/or wire guidance. Fixed-diameter and balloon dilator designs include 'through-the-scope' ('TTS') and 'non-TTS' types. The endoscope accessory channel must accommodate TTS dilators. Most push-type dilators are non-TTS devices, except those used for pancreatico-biliary applications.

Guidewires may be used to facilitate delivery of dilating devices to strictures throughout the gastrointestinal tract and can be passed via endoscopy with or without fluoroscopy. Wire-guided TTS dilators are passed over a guidewire and through the endoscope accessory channel. Non-TTS wire-guided dilators are passed over a guidewire following initial endoscopic guidewire placement and subsequent endoscope removal. A variety of specialty wires with flexible coil tips, stiff shafts, and external measurement markers are available.

Push-type fixed-diameter dilators   

Push-type fixed-diameter dilators come in a variety of designs, calibers, and lengths. They are sold individually and in sets of varying calibers. Most fixed-diameter dilators are marketed as reprocessable multi-use devices.

Hurst and Maloney dilators   

Hurst and Maloney (Medovations, Milwaukee, WI) dilators, also referred to as 'bougies', are fixed-diameter push-type dilators that do not accommodate a guidewire [73–75]. They are internally weighted with mercury or tungsten for gravity assistance when passed with the patient in the upright position. Hurst dilators have a blunt rounded tip, while Maloney dilators have an elongated tapered tip. Patients may be instructed to use these devices for self-dilation.

Savary-type dilators   

Savary-type dilators are flexible taper-tipped polyvinyl chloride cylinders with a central channel for passage over a guidewire. Savary-Gilliard® (Wilson-Cook Medical, Inc, Winston-Salem, NC) dilators have a long tapered tip and a radiopaque marking at the base of the taper designating the point of maximal dilating caliber.

American Dilation System dilators   

American Dilation System® (CRBard, Inc, Billerica, MA) dilators have a shorter taper tip and total radiopacity throughout their length.

TTS fixed diameter dilators   

TTS fixed diameter dilators are tapered, guidewire-compatible plastic cylinders, developed for ERCP-mediated dilation of pancreatico-biliary strictures. They are passed over a guidewire through the accessory channel of the endoscope. They are equipped with a radiopaque band just proximal to the taper to indicate the point of maximal dilation.

Threaded-tip stent retrievers   

Threaded-tip stent retrievers have also been used to dilate very tight pancreatico-biliary and esophageal strictures that otherwise allow only passage of a guidewire [76–78]. The wire-guided screw-tipped device is used to auger through high-grade stenoses. A modified device is now commercially available as a dilator (Wilson-Cook Medical, Inc., Winston-Salem, NC).

Radial expanding balloon dilators   

Radial expanding balloon dilators are available in an array of designs, lengths, and calibers for various purposes. Balloon dilators are made of low-compliance, non-latex materials that allow uniform and reproducible expansion to their specified diameter at maximum inflation. One platform of balloon dilator is designed to expand to specific incremental calibers at sequentially higher pressures. Dilating balloons are expanded by pressure injection of liquid (e.g. water, radiopaque contrast), except for those designed for use in achalasia where air is used instead of fluid. The hydraulic pressure of the balloon may be monitored manometrically to gauge radial expansion force. Inflation with full-strength or dilute radiopaque contrast enhances fluoroscopic observation. Most dilating balloons are marketed as single-use items.

TTS dilators   

TTS balloon dilators can be used in any accessible region of the gastrointestinal tract including the pancreatico-biliary tree. Non-TTS balloon dilators are wire-guided and primarily intended for use in the esophagus and distal colon.

Achalasia balloon dilators   

Achalasia balloon dilators are large diameter (30, 35, and 40 mm), non-TTS, wire-guided radial expansion balloon dilators that are designed for achalasia but have also been used in other disease states [79–81]. A variety of designs used historically have been supplanted by the current non-radiopaque graded-size polyethylene balloons. They are positioned across the esophagogastric junction using fluoroscopic and/or endoscopic guidance. Insufflation with air is monitored manometrically. Some commercially available achalasia dilators are marketed for reuse.

 Conclusion   

Several manufacturers have developed a variety of endoscope models. Procedure-specific endoscopes are designed to enhance endoscopic diagnosis and therapy. An extensive array of accessory devices have been developed and adopted for diagnostic and therapeutic endoscopy. These innovations and adaptations have enabled the expansion of minimally invasive endoscopic therapies for benign and neoplastic diseases of the digestive tract. Countless lives have been saved, surgical procedures avoided, and societal benefits accrued, as a result of the development and dissemination of endoscope and endoscopic accessories and the techniques they enable. We are indebted to the legions of physician endoscopists and their industry counterparts who contributed to endoscope and device development and evaluation. Continuous creative innovation will see to the further advancement of these tools.

 Outstanding issues and future trends   

Modern endoscopy has brought forth many advances in direct imaging. The evolution of fiber optic to digital imaging has enabled further image quality enhancement and miniaturization. Efforts are underway to develop optical biopsy techniques that would allow accurate and reliable tissue discrimination without the need for tissue sampling. This might better enable identification of dysplastic tissue, otherwise indiscriminate by standard white-light endoscopy. Examples include light immunofluoresence spectroscopy, optical coherence tomography, and narrow-band imaging.

Scope designs are underway that will allow better function of accessories. Examples include attachments to duodenoscopes for fixing guidewires in place and holsters to seat ERCP catheters. Dedicated operating endoscopes will be developed as endoluminal and extraluminal endoscopic therapies emerge. Scope handle ergonomics are apt to evolve to include remote controlled, self-propelling, and power-steered endoscopes. Lastly, miniaturization will permit further reduction in instrument diameters.

Tissue sampling and resection devices continue to evolve and improve. Devices to allow large area en bloc mucosal resection are being displayed. Full-thickness resection devices are sure to be developed in our professional lifetimes. Plicating devices developed for endoluminal antireflux therapies are apt to have broad applications in hemostasis, resection, and bariatric procedures.

We expect to see further application of advanced computing techniques (such as neural networks) incorporated into '"intelligent'" endoscopes. Eventually the capsule concept may incorporate automatic therapeutic devices.

Continuing ingenuity and collaboration between physicians and engineers will certainly provide important new tools in the future.

 References  

 1 Sivak, MV. Endoscopic technology: is this as good as it gets? 1999; 50: 718–21.

 2 Barlow, DE. (2000). Flexible endoscopic technology: the video image endoscope. In: Gastroenterologic endoscopy, 2^nd edn (ed. Sivak MV) , pp. 29–49. W.B. Saunders, Philadelphia.–

 3 Kawahara, I & Ichikawa, H. (2000). Flexible endoscopic technology: the fiberoptic endoscope. In: Gastroenterologic Endoscopy, 2^nd edn , pp. 16–28. W.B. Saunders, Philadelphia., , –

 4 Schuman, BM & Kowalski, TE. (2002). The history of the endoscope. In: Gastrointestinal disease: an endoscopic approach, 2^nd edn (ed. Marino AJ, Benjamin SB&), pp. 1–13. Slack, Thorofare, NJ. –

 5 Eisen, MD, Dominitz, JA & Faigel, DO. Enteroscopy. Gastrointest Endosc 2001; 53: 871–3. PubMed

 6 Chen, YK & Powis, ME. The structure and function of the video image endoscope. In: Gastrointestinal disease: an endoscopic approach, 2^nd edn , pp. 16–23. Slack, Thorofare, NJ. ,  & , &, –

 7 Nelson, DB, Block, KP & Bosco, JJ. High resolution and high magnification endoscopy. Gastrointest Endosc 2000; 52: 864–6. PubMed

 8 Chak, A, Koehler, MK & Sundaram, SN. Diagnostic and therapeutic impact of push enteroscopy: analysis of factors associated with positive findings. Gastrointest Endosc 1998; 47 (1): 18–22. PubMed

 9 Nelson, DB, Bosco, JJ & Curtis, WD. Technology status evaluation report: duodenoscope-assisted cholangiopancreatography. Gastrointest Endosc 1999; 50: 943–5.

10 Carr-Locke, DL, Branch, MS & Byrne, WJ. Tissue sampling during endosonography. Gastrointest Endosc 1998; 47: 576–8. PubMed

11 Ginsberg, GG. Variable stiffness colonoscope. Gastrointest Endosc 2003; 58: 579–84. PubMed

12 Nelson, DB, Bosco, JJ & Curtis, WD et al. Technology status evaluation: sheathed endoscopes. Gastrointest Endosc 1999; 49: 862–4. PubMed

13 Ginsberg, GG, Barkun, AN, Bosco, JJ, Isenberg, GA, Nguyen, CC, Petersen, BT, , , ,  & ,  et al. Wireless capsule endoscopy. Gastrointest Endosc 2002; 56: 621–4. PubMed

14 Bernstein, DE, Barkin, JS, Reiner, DK, Lubin, J, Phillips, RS & Grauer, L. Standard biopsy forceps versus large-capacity forceps with and without needle. Gastrointest Endosc 1995; 41: 573–6. PubMed

15 Levine, DS. et al. Safety of a systematic endoscopic biopsy protocol in patients with Barrett's esophagus. Am J Gastroenterol 2000; 95: 1152–7. PubMed

16 Fantin, AC, Neuweiler, J, Binek, JS, Suter, WR & Meyenberger, C. Diagnostic quality of biopsy forceps specimens: comparison between a conventional biopsy forceps and multibite forceps. Gastrointest Endosc 2001; 54: 600–4. PubMed CrossRef

17 Gilbert, DA, DiMarino, AJ & Jensen, DM et al. Status evaluation: hot biopsy forceps. Gastrointest Endosc 1992; 38: 753–6. PubMed

18 Carr-Locke, DL, Al-Kawas, FH & Branch, MS et al. Technology assessment status evaluation: bipolar and multipolar accessories. Gastroenterol Nurs 1998; 21: 187–9. PubMed

19 Vanagunas, A, Pothen, J & Nimcsh, V. Adequacy of 'hot biopsy' for the treatment of diminutive polyps: a randomized trial. Am J Gastroenterol 1989; 84: 383–5. PubMed

20 Peluso, F & Golodner, F. Follow-up of hot biopsy forceps treatment of diminutive colonic polyps. Gastrointest Endosc 1991; 37: 604–6. PubMed

21 Yang, R, Naritoku, W & Laine, L. Prospective, randomized comparison of disposable and reusable forceps in gastrointestinal endoscopy. Gastrointest Endosc 1994; 40: 671–4. PubMed

22 Woods, KL, Anand, BS & Cole, RA et al. Influence of endoscopic biopsy forceps characteristics on tissue specimens: results of a prospective randomized study. Gastrointest Endosc 1999; 49: 177–83. PubMed

23 Yang, R, Ng, S, Nichol, M & Laine, L. A cost and performance evaluation of disposable and reusable biopsy forceps in GI endoscopy. Gastrointest Endosc 2000; 51: 266–70. PubMed

24 Deprez, PH, Horsmans, Y, Van Hassel, M, Hoang, P, Piessevaux, H & Geubel, A. Disposable versus reusable biopsy forceps: a prospective cost evaluation. Gastrointest Endosc 2000; 51: 262–5. PubMed

25 Rizzo, J, Bernstein, D & Gress, F. A performance, safety and cost comparison of reusable and disposable endoscopic biopsy forceps: a prospective, randomized trial. Gastrointest Endosc 2000; 51: 257–61. PubMed

26 Kozarek, RA, Attia, FM & Sumida, SE et al. Reusable biopsy forceps: a prospective evaluation of cleaning, function, adequacy of tissue specimen, and durability. Gastrointest Endosc 2001; 53: 747–50. PubMed CrossRef

27 Bronowicki, J-P, Venard, V, Botté, C, Monhoven, N, Gastin, I & Choné, L et al. Patient-to-patient transmission of hepatitis C virus during colonoscopy. N Engl J Med 1997; 337: 237–40. PubMed

28 De Bellis, M. et al. Tissue sampling at ERCP in suspected malignant biliary strictures (Part 1). Gastrointest Endosc 2002; 56: 552–61. PubMed CrossRef

29 De Bellis, M. et al. Tissue sampling at ERCP in suspected malignant biliary strictures (Part 2). Gastrointest Endosc 2002; 56: 720–30. PubMed CrossRef

30 Casco, C. et al. A new device for abrasive cytology sampling during upper gastrointestinal endoscopy: experience in infectious and neoplastic diseases. Endoscopy 1999; 31: 348–51. PubMed

31 Biliary and pancreatic sampling devices during ERCP. Gastrointest Endosc 1996; 43:775–8.

32 Howell, DA. et al. Endoscopic needle aspiration biopsy at ERCP in the diagnosis of biliary strictures. Gastrointest Endosc 1992; 38: 531–5. PubMed

33 Hwang, JH & Kimmey, MB. The incidental upper gastrointestinal subepithelial mass. Gastroenterology 2004: 126: 301–7. PubMed CrossRef

34 Forde, KA, Treat, MR & Tsai, JL. Initial clinical experience with a bipolar snare for colon polypectomy. Surg Endosc 1993; 7: 427–8. PubMed CrossRef

35 Tappero, G, Gaia, E & De Giuli, P et al. Cold snare excision off small colorectal polyps. Gastrointest Endosc 1992; 38: 310–13. PubMed

36 McAfee, JH & Katon, RM. Tiny snares prove safe and effective for removal of diminutive polyps. Gastrointest Endosc 1994; 40: 301–13. PubMed

37 Nelson, DB, Bosco, JJ & Curtis, WD et al. ASGE technology status evaluation report: endoscopic retrieval devices. Gastrointest Endosc 1999; 50: 932–4. PubMed

38 Ginsberg, GG. Management of ingested foreign bodies and food bolus impactions. Gastrointest Endosc 1995; 41: 33–8. PubMed

39 Faigel, DO, Stotland, BR, Kochman, ML, Hoops, T, Judge, T & Kroser, J, et al'. Device choice and experience level in endoscopic foreign object retrieval: an in vivo study. Gastrointest Endosc 1997; 45: 490–2. PubMed

40 Nelson, DB, Bosco, JJ & Curtis, WD et al. Injection needles. Gastrointest Endosc 1999; 50: 928–31. PubMed

41 Brooker, JC, Saunders, BP, Shah, SG, Thapar, CJ, Thomas, HJ & Atkin, WS et al. Total colonic dye-spray increases the detection of diminutive adenomas during routine colonoscopy: a randomized controlled trial. Gastrointest Endosc 2002; 56: 333–8. PubMed

42 Nelson, DB, Barkun, AN & Block, KP et al. Endoscopic hemostatic devices. Gastrointest Endosc 2001; 54: 833–40. PubMed

43 Laine, L. Bipolar/multipolar electrocoagulation. Gastrointest Endosc 1990; 36 (Suppl.): S38–S41. PubMed

44 Carr-Locke, DL, Conn, MI, Faigel, DO, Laing, K, Leung, JW & Mills, MR et al. Developments in laser technology. Gastrointest Endosc 1998; 48: 711–16. PubMed

45 Ginsberg, GG, Barkun, AN & Bosco, JJ et al. The argon plasma coagulator. Gastrointest Endosc 2002; 55: 807–10. PubMed

46 Cipolletta, L, Bianco, MA, Rotondano, G, Piscopo, R, Prisco, A & Garofano, ML. Prospective comparison of argon plasma coagulator and heater probe in the endoscopic treatment of major peptic ulcer bleeding. Gastrointest Endosc 1998; 48: 191–5. PubMed

47 Zlatanic, J, Waye, JD, Kim, PS, Baiocco, PJ & Gleim, GW. Large sessile colonic adenomas: use of argon plasma coagulator to supplement piecemeal snare polypectomy. Gastrointest Endosc 1999; 49: 731–5. PubMed

48 Brooker, JC, Saunders, BP, Shah, SG, Thapar, CJ, Suzuki, N & Williams, CB. Treatment with argon plasma coagulation reduces recurrence after piecemeal resection of large sessile colonic polyps: a randomized trial and recommendations. Gastrointest Endosc 2002; 55: 371–5. PubMed

49 Low, DE & Kozarek, RA. Snare debridement prior to Nd:YAG photoablation improves treatment efficiency of broad-based adenomas of the colorectum. Gastrointest Endosc 1989; 35: 288–91. PubMed

50 El-Newihi, HM & Achord, JL. Emerging role of endoscopic variceal band ligation in the treatment of esophageal varices. Dig Dis 1996; 14: 201–8. PubMed

51 Slosberg, EA & Keeffe, EB. Sclerotherapy versus banding in the treatment of variceal bleeding. Clin Liver Dis 1997; 1: 77–84. PubMed

52 Laine, L & Cook, D. Endoscopic ligation compared with sclerotherapy for treatment of esophageal variceal bleeding: a meta-analysis. Ann Intern Med 1995; 123: 280–7. PubMed

53 Stiegmann, GV, Goff, JS, Sun, JH, Hruza, D & Reveille, RM. Endoscopic ligation of esophageal varices. Am J Surg 1990; 159: 21–5. PubMed

54 Hachisu, T. Evaluation of endoscopic hemostasis using an improved clipping apparatus. Surg Endosc 1988; 2: 13–17. PubMed CrossRef

55 Hachisu, T, Yamada, H, Satoh, S & Kouzu, T, . Endoscopic clipping with a new rotatable clip-device and a long clip. Digestive Endoscopy 1996; 8: 127–33.

56 Cipolletta, L, Bianco, MA, Rotonano Gcatalano, M, Prisco, A & De Simone, T. Endoclip-assisted resection of large pedunculated colon polyps. Gastrointest Endosc 1999; 50: 405–6. PubMed

57 Uno, Y, Satoh, K & Tuji, K et al. Endoscopic ligation by means of clip and detachable snare for management of colonic postpolypectomy hemorrhage. Gastrointest Endosc 1999; 49: 113–15. PubMed

58 Parra-Blanco, A, Kaminaga, N & Kojima, T et al. Hemoclipping for postpolypectomy and postbiopsy bleeding. Gastrointest Endosc 2000; 51: 37–41. PubMed

59 Yoshikane, H, Hidano, H & Sakakibara, A et al. Endoscopic repair by clipping of iatrogenic colonic perforation. Gastrointest Endosc 1997; 46: 464–6. PubMed

60 Pontecorvo, C & Pesce, G. The 'safety snare': a ligature placing snare to prevent hemorrhage after transection of large pedunculated polyps. Endoscopy 1986; 18: 55–6. PubMed

61 Hachisu, T. A new detachable snare for hemostasis in the removal of large polyps or other elevated lesions. Surg Endosc 1991; 5: 70–4. PubMed CrossRef

62 Uno, Y, Satoh, K, Tuji, K, Wada, T, Fukuda, S, Saito, H & Munakata, A. Endoscopic ligation by means of clip and detachable snare for management of colonic post polypectomy hemorrhage. Gastrointest Endosc 1999; 41: 113–15.

63 Rey, JF, Marek, DA, Cotton, P & , . Endoloop in the prevention of post polypectomy bleeding: preliminary results. Gastrointest Endosc 1997; 46: 387–9. PubMed

64 Matsushita, M, Hajiro, K & Takakuwa, H et al. Ineffective use of detachable snare for colonoscopic polypectomy of large polyps. Gastrointest Endosc 1998; 47: 496–9. PubMed

65 Iishi, H, Tatsuta, M, Narahara, H, Iseki, K & Sakai, N. Endoscopic resection of large pedunculated colorectal polyps using detachable snare. Gastrointest Endosc 1996; 44: 594–7. PubMed

66 Tada, M, Inoue, H, Yabata, E, Okabe, S & Endo, M. Feasibility of the transparent cap-fitted colonoscope for screening and mucosal resection. Dis Colon Rectum 1997; 40: 618–21. PubMed

67 Nelson, DB, Block, KP & Bosco, JJ et al. Technology status report evaluation: endoscopic mucosal resection. Gastrointest Endosc 2000; 52: 860–3. PubMed

68 Tada, M, Inoue, H, Yabata, E, Okabe, S & Endo, M. Colonic mucosal resection using a transparent cap-fitted endoscope. Gastrointest Endosc 1996; 44: 63–5. PubMed

69 Oshitani, N, Hamasaki, N, Sawa, Y, Hara, J, Nakamura, S & Matsumoto, T et al. Endoscopic resection of small rectal carcinoid tumors using an aspiration method with a transparent overcap. J Int Med Res 2000; 28: 241–6. PubMed

70 Matsushita, M, Hajiro, K, Okazaki, K, Takakuwa, H & Tominaga, M. Efficacy of total colonoscopy with a transparent cap in comparison with colonoscopy without the cap. Endoscopy 1998; 30: 444–7. PubMed

71 Dafnis, GM. Technical considerations and patient comfort in total colonoscopy with and without a transparent cap: initial experiences from a pilot study. Endoscopy 2000; 32: 381–4. PubMed CrossRef

72 Abele, JE. The physics of esophageal dilatation. Hepatogastroenterology 1992; 39: 486–9. PubMed

73 Patterson, DJ, Graham, DY, Smith, JL, Schwartz, JT, Lanza, FL & Cain, GD. Natural history of benign esophageal stricture treated by dilatation. Gastroenterology 1983; 85: 346–50. PubMed

74 Cox, JG, Winter, RK, Maslin, SC, Dakkak, M, Jones, R, Buckton, GK, , , ,  & ,  et al. Balloon or bougie for dilatation of benign esophageal stricture? Dig Dis Sci 1994; 39: 776–81. PubMed

75 Wesdorf, IC, Bartelsman, JF, den Hartog Jager, FC, Huibregtse, K & Tytgat, GN. Results of conservative treatment of benign esophageal strictures: a follow-up study in 100 patients. Gastroenterology 1982; 82: 487–93. PubMed

76 Faigel, DO, Ginsberg, GG & Kochman, ML. Innovative use of the Soehendra stent retriever for biliary stricture recanalization [Letter]. Gastrointest Endosc 1996; 44: 635. PubMed

77 Ziebert, JJ & Disario, JA. Dilation of refractory pancreatic duct strictures: the turn of the screw. Gastrointest Endosc 1999; 49: 632–5. PubMed

78 Parasher, VK. A novel approach to facilitate dilation of complex non-traversable esophageal strictures by efficient wire exchange using a stent pusher. Gastrointest Endosc 2000; 51: 730–1. PubMed CrossRef

79 Vaezi, MF & Richter, JE. Current therapies for achalasia: comparison and efficacy. J Clin Gastroenterol 1998; 27: 21–35. PubMed CrossRef

80 Vaezi, MF & Richter, JE. Practice guidelines: diagnosis and management of achalasia. —Am J Gastroenterol 1999; 12: 3406–12.

81 Virgilio, C, Cosentino, S, Favara, C, Russo, V & Russo, A. Endoscopic treatment of postoperative colonic strictures using an achalasia dilator: short-term and long-term results. Endoscopy 1995; 27: 219–22. PubMed

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