Endoscopy Practice and Safety
Peter B. Cotton ed.
4. Endoscopic equipment
Gregory G. Ginsberg
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 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 . 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 However, fiber-optic image guides have largely been replaced by copper wire that transmits digital information, from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.
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) . 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.
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.
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 180230°.
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.
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.
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×) . Endoscope imaging is detailed in the following chapter (Aabakken).
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/airwater 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.
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 (5.112.8 mm), working length (9251100 mm), and instrument channel size (2.06.0 mm) and number (12). Specialty features may also include oblique viewing, ultra thin design, and video zoom capability. List prices range from
$13 700 to $24 900.
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 (5.011.7 mm), working length (2180800 mm), and instrument channel size (1.03.5 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.
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 (1030250 mm), insertion tube diameter (7.412.6 mm), and channel size (2.04.8 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.
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 (1870900 mm), insertion tube diameter (2.83.4 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 .
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 (9751325 mm), insertion tube diameter (7.913.7 mm), instrument channel size (2.23.7 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). 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.
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 (1330700 mm), insertion tube diameter (11.113.7 mm), instrument channel size (2.84.2 mm), and number (12). 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 .
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 (630790 mm), insertion tube diameter (12.213.3 mm), and instrument channel size (3.24.2 mm). List prices range from $5250 to $15 100. A disposable, sheathed sigmoidoscope is also commercially available .
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 . 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 30120 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 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 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
. 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 23× 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 .
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 . 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 . Heat energy is regulated and determined by generator voltage and waveform, current density, and application time . Bipolar hot biopsy forceps have also been developed. Bipolar forceps have insulated biopsy cups except for the cup edges,
which are the electrodes . Tissue injury is deeper with monopolar hot biopsy forceps than with bipolar forceps .
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 . 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
Yang et al. prospectively measured cost and operational performance of disposable and reusable forceps in 200 biopsy sessions . Reusable costs factored in acquisition and reprocessing. They found that malfunction of reusable forceps increased with
number of uses. At up to 1520 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 . 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 . 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 . 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 .
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.
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 68 Fr [28,29]. A cytology balloon for non-endoscopic esophageal cytological screening and surveillance for infectious and neoplastic diseases
has been described .
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 . 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 . 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 . EUS-guided fine-needle aspiration is covered in the Endoscopic Ultrasound section.
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 . In monopolar snares the current flows from the snare to a distant return electrode (grounding pad), generating local thermal
energy for cutting and coagulation . 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 .
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
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 . 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.
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 . 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 . Over-tubes of both standard length that bypass the upper esophageal sphincter and longer 4560 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 .
Injection devices include injection needles, spray catheters, and ERCP catheters.
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),
Injection needles consist of an outer sheath (plastic, Teflon, or stainless steel coil) and an inner hollow core needle (2125G) (Fig. 11). 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 2.32.8 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 are used when performing chromoendoscopy. Chromoendoscopy employs a chromic agent to enhance the detection
or discrimination of dysplastic epithelia . 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 .
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.
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
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 . Non-contact thermal devices include laser fibers and argon plasma beam coagulators .
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 . 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 transmit collimated, highly energized light energy, emitting a focused monochromatic beam . 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 . 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 plasmatissue 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 .
The operative distance of the probe from the target tissue is 28 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
. 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 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 8691% 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, MalloryWeiss 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 34 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 . 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 . The latter application should be limited to use in highly selected instances.
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 .
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 . 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 .
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.
Plastic transparent caps that affix to and overhang the tip of the endoscope may be used to enhance colonic visualization
and to facilitate EMR . 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). 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 . Cap-assisted EMR may also be used for completion resection of flat or sessile lesions not amenable to other mucosectomy
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.
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 . 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 . 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 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 . 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 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 . 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.
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
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
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