Table of Contents
Dedication
Title page
Copyright page
List of Video Clips
Preface
About the companion website
SECTION 1: Pre-procedure
CHAPTER 1: The Endoscopy Unit, Colonoscope, and Accessories
Introduction
The procedure rooms
The non-procedure areas
The colonoscope
Endoscopic accessories
Summary
CHAPTER 2: The Role of the Endoscopy Assistant during Colonoscopy
Introduction
Certification and training
Pre-colonoscopy tasks
Intra-colonoscopy tasks
Post-procedure tasks
CHAPTER 3: Indications and Contraindications for Colonoscopy
Introduction
Specific indications
Pediatric colonoscopy
Summary
CHAPTER 4: Preparation for Colonoscopy
Introduction
Management of standing medications
Colon cleansing
Informed consent
Summary
SECTION 2: Basic Procedure
CHAPTER 5: Sedation for Colonoscopy
Introduction
Levels of sedation
Pharmacology of drugs
Approaches to sedation for colonoscopy
Pre-colonoscopy management
Post-colonoscopy management
Equipment for sedation
Staffing and colonoscopic sedation
Summary
CHAPTER 6: Colonoscopy Technique: The Ins and Outs
Introduction
Preparation for scope insertion
Proper technique for holding the scope
Colonic intubation: segment by segment
Withdrawal phase of colonoscopy
Special techniques to increase visualization
Summary
CHAPTER 7: Colonoscopic Findings
Colorectal cancer
Colorectal polyps
Anal carcinoma
Diverticulosis
Hemorrhoids
Ischemic colitis
Solitary rectal ulcer
Radiation colopathy and proctopathy
Diversion colitis
Inflammatory bowel disease
Endoscopy of ileal pouches
Vascular ectasias
Graft-versus-host disease
Infectious colitis
Dieulafoy lesions
Microscopic, lymphocytic, and collageneous colitis
CHAPTER 8: Diagnostic Biopsy
Introduction
Equipment for biopsy
How to use biopsy forceps
What to do with the biopsy
When to take a biopsy
Biopsy in special settings
Summary
SECTION 3: Operative Procedures
CHAPTER 9: Thermal Techniques: Electrosurgery, Argon Plasma Coagulation, and Laser
Introduction
Electrosurgery
Instruments used for electrosurgery
Common uses of electrocautery
General precautions for electrosurgery
Argon plasma coagulation
Laser
Summary
CHAPTER 10: Basic Principles and Techniques of Polypectomy
Introduction
Polyp appearance, location, and prevalence
Polyp histopathology
Detecting polyps
General principles of polypectomy
Polypectomy: small polyps
Polypectomy: Pedunculated polyps
Summary
CHAPTER 11: Difficult Polypectomy
Introduction
Options when encountering difficult polyps
Characteristics of the polyp
Characteristics of the procedure
Clinical status of the patient
The resources of the endoscopy facility
Expertise available locally
The characteristics of the colonoscopist
Colonoscopic resection of the difficult polyp: Preparation
Colonoscopic resection of the difficult polyp: Technique
Special situations and techniques
Summary
CHAPTER 12: Management of Malignant Polyps
Introduction
Can I recognize a malignant polyp by its gross appearance?
If I think it may be malignant, should I still undertake polypectomy?
Resection of a polyp that might be malignant
Marking the site
The unsuspected malignant polyp
Decision-making after resection of a malignant polyp
If biopsy of a polyp reveals malignancy, is there a role for colonoscopic resection?
Summary
CHAPTER 13: Therapeutic Colonoscopy
Introduction
Relief of colonic obstruction
Treatment of pseudo-obstruction
Intralesional drug injection
Closure of perforation or fistula
Non-thermal treatment of bleeding sites
Removal of foreign body
Summary
CHAPTER 14: Complications of Colonoscopy
Introduction
Cardiopulmonary complications
Perforation
Postpolypectomy coagulation syndrome
Hemorrhage
Rare complications of colonoscopy
Complications related to the bowel preparation
Immediate post-procedural abdominal pain due to intraluminal gas
Summary
SECTION 4: Current and Future Considerations
CHAPTER 15: Quality in Colonoscopy
Introduction
Specific quality metrics in colonoscopy
Endoscope reprocessing and infection control
The endoscopy report and flow sheet
Summary
CHAPTER 16: Teaching and Training in Colonoscopy
Introduction and background
Costs of training: safety and economic issues
Principles for successful hands-on colonoscopy training
Continuing education
Other learning tools
Measuring competence
Summary
CHAPTER 17: Computed Tomographic Colonography (“Virtual” Colonoscopy)
Introduction
The CTC procedure
CTC performance
Indications
Barium enema
Summary
CHAPTER 18: Advanced Imaging Techniques
Introduction
Chromoendoscopy
Water method of colonoscopy
New technologies
Summary
CHAPTER 19: The Future of Colonoscopy
Introduction
Toward a therapeutic procedure
Toward a better catharsis
Toward less or no anesthesia
Toward simpler tissue sampling
Toward decreasing the polyp miss rate
Toward decreasing incomplete resection
Toward “resect and discard”
Toward better identification of resectable malignant polyps
Toward tube-less colonoscopy
Toward transmural surgery
Toward other novel therapies
Summary
Supplemental Images
Index
The authors would like to dedicate the book to Marguerite (JDW), Suzanne (JA) and Liz, Jessica and Fern (PHR).
This edition first published 2013 © 2013 by John Wiley & Sons, Ltd.
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Library of Congress Cataloging-in-Publication Data
Waye, Jerome D., 1932–
Practical colonoscopy / Jerome D. Waye, James Aisenberg, Peter H. Rubin ; With the assistance of Shannon Morales.
p. ; cm.
Includes bibliographical references and index.
ISBN 978-0-470-67058-3 (hardback : alk. paper)
I. Aisenberg, James. II. Rubin, Peter H. III. Title.
[DNLM: 1. Colonoscopy–methods. 2. Colonic Diseases–diagnosis. 3. Colonic Diseases–surgery. WI 520]
616.3'407545–dc23
2012044841
A catalogue record for this book is available from the British Library.
Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books.
Cover image: Micrograph © iStockphoto/beholdingEye; all other images courtesy of the authors.
Cover design by Meaden Creative
List of Video Clips
All videos are accompanied by audio commentary.
Video Clip 7.1 Melanosis coli with polyp
An adenoma is hidden behind the ileocecal valve in the setting of melanosis coli.
Video Clip 7.2 Squamous papillomas in the rectum
Multiple diminutive papules are seen near the dentate line during careful retroflex examination.
Video Clip 7.3 Diverticular colitis
Prominent polypoid red folds seen in a patient with sigmoid colon diverticular disease.
Video Clip 7.4 Segmental colonic ischemia
A segment of sigmoid colon is involved with moderate to severe ischemia.
Video Clip 7.5 Solitary rectal ulcer syndrome
Endoscopic findings of solitary rectal ulcer syndrome include ulceration, erythema, edema, and exudate.
Video Clip 7.6 Radiation proctopathy
Angioectasias in the rectum treated with argon plasma coagulation therapy.
Video Clip 7.7 Cobble-stoning in chronic ulcerative colitis
Severe edema, erythema, and ulceration in a patient with active ulcerative colitis.
Video Clip 7.8 Small carcinoma in chronic ulcerative colitis
Small carcinoma detected during surveillance in chronic ulcerative colitis. Extensive mucosal scarring is also seen.
Video Clip 7.9 Large carcinoma in chronic colitis
Large carcinoma in colitis, mucosal bridging is seen and snare biopsy technique is used.
Video Clip 7.10 Dysplasia in ulcerative colitis
The spray catheter is used for chromoendoscopy, which reveals a dysplastic plaque.
Video Clip 7.11 Nodular carcinoma arising in ulcerative colitis
Small, nodular carcinoma detected during surveillance in patient with chronic ulcerative colitis.
Video Clip 7.12 Chromoendoscopy in colitis surveillance
Areas of flat dysplasia are detected during chromoendoscopy in colitis surveillance.
Video Clip 7.13 Sessile dysplasia in chronic ulcerative colitis
Large area of villiform, sessile dysplasia is seen in chronic ulcerative colitis.
Video Clip 7.14 Giant inflammatory polyp
Giant inflammatory polyp identified in chronic colitis.
Video Clip 7.15 Dysplastic polyp in ulcerative colitis
Identification and snare resection of flat, dysplastic polyp in chronic ulcerative colitis.
Video Clip 7.16 Bleeding angioectasia
Detection and cauterization of ascending colon, bleeding angioectasia.
Video Clip 7.17 Pinworms
Live pinworms seen during colonoscopy.
Video Clip 7.18 Ascaris
Live Ascaris worm seen during colonoscopy.
Video Clip 7.19 Flat adenoma in microscopic colitis
Large flat adenoma seen in ascending colon in a patient with microscopic colitis. The colitis has caused edema and a mosaic pattern, which is atypical for this disease.
Video Clip 10.1 Sessile serrated adenoma/polyp
Multiple examples of identification and resection of sessile serrated adenomas/polyps are provided.
Video Clip 10.2 Resection of sessile serrated polyp
Sessile serrated adenoma/polyp identified and resected with saline lift followed by piecemeal snare polypectomy.
Video Clip 10.3 Giant lipoma
Giant, pedunculated lipoma with erythema related to trauma.
Video Clip 10.4 Ileal carcinoid
Intubation of the ileum reveals a 1.5-cm submucosal carcinoid.
Video Clip 11.1 Detachable loop and pedunculated polypectomy
The detachable loop is used to promote hemostasis before resection of this large, pedunculated polyp.
Video Clip 11.2 Piecemeal polypectomy, argon plasma coagulation, and net retrieval of fragments
The sequence of saline injection, piecemeal polypectomy, and argon plasma coagulation and net retrieval of polyp fragments is used to eradicate this 3-cm adenoma.
Video Clip 11.3 Piecemeal resection of sessile adenoma
Large sessile adenoma removed piecemeal following saline lift.
Video Clip 11.4 Saline-assisted polypectomy
Multiple injection sites are used to elevate the polyp with methylene blue and saline.
Video Clip 11.5 The non-lifting sign
This polyp does not lift with saline injection, suggesting the presence of malignancy.
Video Clip 11.6 Giant villous adenoma
This enormous sigmoid adenoma occupied the entire lumen and is debulked. Water immersion is used to examine the defect for signs of residual polyp, which are ablated with the argon plasma coagulator.
Video Clip 11.7 Cecal retroflexion with polypectomy
A large, right-colon polyp is hidden behind a fold and identified and removed in retroflexion.
Video Clip 11.8 Flat right colon polyp
A flat right-colon polyp is seen and resected in retroflexion.
Video Clip 12.1 Familial adenomatous polyposis
Innumerable adenomas seen in a patient with familial adenomatous polyposis.
Video Clip 12.2 The Non-Lifting Sign
3 cm malignant polyp in ascending colon which exhibits the non-lifting sign upon sub-mucosal saline injection.
Video Clip 12.3 Malignant sessile polyp
A 2-cm sessile malignant polyp removed with saline injection and snare polypectomy.
Video Clip 13.1 Dilation of strictured anastomosis
Strictured ileocolic anastomosis dilated with a through-the-scope balloon.
Video Clip 13.2 Foreign body in sigmoid
A chicken bone is identified embedded in the colon wall, and is removed with the snare.
Video Clip 14.1 Giant rectal polyp with bleeding
Snare resection of giant rectal polyp complicated by post-polypectomy hemorrhage, managed colonoscopically.
Video Clip 14.2 Immediate postpolypectomy bleeding: sessile polyp
Arterial bleeding seen following snare polypectomy. Clip placement used to achieve hemostasis.
Video Clip 14.3 Immediate postpolypectomy bleeding: pedunculated polyp
Bleeding from pedicle of polyp is controlled with compression and with clip placement.
Video Clip 14.4 Delayed postpolypectomy bleeding
Unprepped colonoscopy used for identification and treatment of bleeding site several days following ascending colon polypectomy.
Video Clip 18.1 Narrow band imaging
Narrow band imaging is used extensively to enhance visualization during resection of this minimally elevated adenoma.
Preface
Approximately 15 million colonoscopies are conducted annually in the USA. This widespread uptake, mirrored in other nations, reflects the power of colonoscopy as a diagnostic and therapeutic tool. Most notably, it is the leading means of preventing death from colorectal cancer, the second leading cause of cancer-related deaths in the USA, and is a first-line test in the management of gastrointestinal bleeding and colitis.
Colonoscopy continues to evolve, owing to enhancements in scope design, image processing, and data management that are offshoots of the modern technology revolution. Novel insights into colonic diseases from contemporary molecular and cell biology are also rapidly advancing the field.
Despite its attributes, colonoscopy remains imperfect. It is a costly, inconvenient, and unpopular procedure that carries some risk. In the USA, at least 50% of adults for whom screening colonoscopy for colon cancer is recommended never receive it, whereas others undergo colonoscopy more frequently than is recommended in expert guidelines. And “interval” colorectal cancer—i.e. cancer detected within 3 years of a “clearing” colonoscopy—is reported in some analyses to occur in as many as 1 in 150 individuals.
Recent studies have underscored the inconvenient truth that colonoscopy quality (safety and effectiveness) varies considerably among practitioners. Accordingly, leaders in the field are promoting quality enhancement measures such as mid-career provider education, implementation of validated quality benchmarks, continuous peer review, and implementation of financial incentives such as pay-for-performance.
Practical Colonoscopy is written with this context in mind. Our goal is to create a succinct, easily readable volume, enhanced by drawings, photos, and videos, which communicates the “nuts and bolts” of high-quality colonoscopy practice. Drawing from our collective experience of over 100 years in the private practice of colonoscopy and gastroenterology, we share the principles and “pearls” we have found most useful. We integrate ideas presented in the recently published, comprehensive, second edition of Colonoscopy: Principles and Practice. We share insights derived from our teaching and research as Professors of Medicine at The Mount Sinai Medical Center in New York. Finally, we present our expectations for forthcoming developments in colonoscopy. Of course, our ultimate hope is that readers will gain an enhanced ability to prevent and treat colonic diseases.
Practical Colonoscopy provides an overview of colonoscopy, while focusing on the practical aspects of quality, indications, and technique. Our objective during the planning and writing of this book was to bring new, practical information to trainees, mid-career colonoscopists, endoscopy assistants, nurses, pathologists, anesthesiologists, and to the motivated lay person who is curious about the science and art of our craft.
The authors wish to acknowledge the use and adaptation of images from Colonoscopy: Principles and Practice, edited by Jerome D. Waye, Douglas K. Rex, Christopher B. Williams. 2nd edition. Blackwell Publishing Ltd; 2009. We thank our medical and surgical colleagues, from whom we have learned so much, and especially the endoscopy staff at the Gastrointestinal Endoscopy Unit at The Mount Sinai Hospital in New York, the staff in our office endoscopy units, our practice partners, patients, and students. Ms. Rebecca Sweeney and Ms. Jennifer Kolb (Icahn School of Medicine at Mount Sinai, Class of 2014) provided invaluable assistance with preparation of the manuscript and videos. We are also grateful to our expert collaborators at Wiley-Blackwell, in particular Ms. Elisabeth Dodds, Mr. Oliver Walter, and Ms. Rebecca Huxley. We thank Jane Fallows and Roger Hulley who have expertly redrawn all line drawings; and Aileen Castell for the help she provided during the production stage. Dr. Shannon Morales, then a 4th-year medical student, was a full collaborator in every aspect of the book, and maintained order in the input submitted at the weekly meetings of the three authors during the many months of drafts, discussions, and eventual agreements. We owe Shannon a special degree of gratitude.
Jerome D. Waye, MD
James Aisenberg, MD
Peter H. Rubin, MD
New York, NY
May 2013
About the companion website
Companion website
This book is accompanied by a website:
www.wiley.com/go/waye/practicalcolonoscopy
The website includes:
SECTION 1
Pre-procedure
CHAPTER 1
The Endoscopy Unit, Colonoscope, and Accessories
Colonoscopy is performed in the hospital, the ambulatory surgical center, or the physician office. Endoscopy units range in size from 1 to 10 or more procedure rooms, and in staffing from one or two to over 50 persons. Regardless of size, staffing, and location, the endoscopy unit must promote safe, efficient, cost-effective, high-quality patient care. A pleasant, comfortable endoscopy facility promotes staff productivity and alleviates patient anxiety. The modern gastrointestinal endoscopy unit is constructed specifically for endoscopic procedures. Specific design concerns include: smooth patient flow; patient privacy; patient safety; spacious procedure rooms; adequate preparation and recovery space; and a pleasant, reassuring environment. The materials must be durable and sanitary, yet aesthetically attractive.
In broad terms, the facility is divided into the administrative area—which is used for patient intake, scheduling, billing, and record maintenance—and the clinical area—which contains the dressing rooms, the pre-procedure area, the procedure rooms, a clean equipment storage area, a cleaning and disinfection zone, and a recovery room. Amenities such as physician–patient consultation rooms, a procedure reporting area, and staff lounge and dressing rooms enhance the quality of the unit.
When building a facility, careful planning and close collaboration between the endoscopists and an architect who possesses expertise in endoscopy unit design is encouraged. The unit design should conform to the practice styles of the endoscopists and the procedure mix and demographics of the practice. Unit construction requires patience (it may take a year to design and construct a new unit), attention to detail, experience, foresight, and cost-sensitivity. As modern endoscopy units are increasingly digitized, specialized expertise in information technology, cabling, and connectivity is essential.
If the facility is built as an ambulatory surgical center or within a hospital, many of the specifics, such as the size of the rooms and corridors, will be regulated. Office-based endoscopy in many states must now meet the criteria of one of the national accrediting organizations. In general, a circular flow of patients works well: the patient moves from the waiting and intake area to the pre-procedure assessment/changing area, to the procedure room, to the recovery/dressing area, and then back to the intake area, where billing and/or new appointment scheduling is completed. The interdependent areas (e.g. procedure and recovery, procedure and scope washing) should be located close to each other. The number of procedure rooms should be projected from the procedure volume of the practice, and will drive the number of overall square feet and all other architectural decisions. The procedure rooms contain the complex, expensive equipment and are the most heavily staffed rooms in the unit. Therefore, the entire facility must be designed to keep the procedure rooms busy with active procedures, rather than also having to serve as recovery rooms.
In the USA, licensing laws generally mandate that the procedure room have a net area of at least 19 m2. This excludes areas occupied by built-ins, such as cabinets or equipment towers, but not area occupied by movable equipment, such as an endoscopic equipment tower. The room must accommodate the equipment and the patient stretcher, and still allow free movement and clear sight lines for the physician, assistant, anesthesiologist and other participants. Because of the amount of equipment required for endoscopy, vertical arrangement of components on towers or carts or in built-in cabinets is generally desirable.
In a modern video-endoscopy room, the central architectural design point is the “physician tower,” which holds the endoscopic light source and image processor. The endoscope is plugged into the processor, and the endoscopist stands immediately in front of the tower. The patient stretcher must be within easy reach of the endoscopist. The distance from the front of the tower to the edge of the patient stretcher should be between 66 and 81 cm, as determined by the length of the scope’s universal cord (Fig 1.1). It is most efficient for the assistant to stand on the opposite side of the stretcher from the endoscopist (Fig 1.2); this location promotes easy access to the patient (e.g. to give abdominal pressure and to monitor respirations), the endoscopist (e.g. to provide a snare for polypectomy), and the other equipment (e.g. the cautery device).
Fig 1.1 Basic clearances in the procedure room.
Fig 1.2 Position of monitors for the colonoscopist and assistant.
Once the positions of the tower and stretcher are established, then the other equipment is located. One video monitor is situated directly across from the endoscopist, establishing a comfortable, clear sight line. The monitor should be mounted at least 1.8 m above the floor. A second endoscopy video monitor is positioned behind the endoscopist for the assistant. The assistant should have clear visual access to the patient, the monitor, and the cardiopulmonary monitoring equipment.
An endoscopic reporting system is often integrated into the room design. This allows nurses and physicians to chart immediately, increasing both accuracy and efficiency. The equipment and electrical cabling must be laid out with forethought: it is unsafe and unkempt to have wires running across the floor. Often an overhead cabling conduit will keep the room tidy but a series of floating ceiling booms will also (expensively) solve the problem. The ancillary equipment should be carefully positioned and handy for the endoscopy assistant. Lighting must be purposeful: the patient’s face and chest should be visible, allowing the assistant to monitor the patient’s color and respiratory pattern, but the ambient lighting should be minimal, to encourage the team to focus on the endoscopic image. The room must be well ventilated with continuous air exchange and adequately soundproofed, and the temperature must be controlled by an independent thermostat.
The waiting and recovery areas also merit careful planning. The total number of required seats in the waiting area depends on the projected case volume of the unit, as well as the procedure and recovery room turnover time. Each patient brings one or more companions; thus, for each patient, at least two seats are required in the waiting area. In general, at least six waiting spaces should be provided for every busy procedure room—two for the patient in recovery, two for the patient in the procedure, and two for the pre-procedure patient. The gastrointestinal endoscopy patient waiting area must be aesthetically pleasant, comfortable, and served by adequate, private bathroom facilities.
The patient changing and pre-procedure areas should be private, secure, and convenient to the procedure area. Depending on the workflow, this area may contain seating for a physician or staff member to perform the pre-procedure interview and obtain informed consent. In some units, the patient walks to the procedure room; in others, the patient lies on a stretcher in the pre-procedure room and intravenous access is obtained in this area.
The recovery bed capacity is a notorious bottleneck in endoscopy units. If colonoscopy takes 45 minutes and recovery takes 45 minutes, one recovery bed will be required per procedure room. In general, this ratio is desirable. The recovery room must permit close patient monitoring and be adequately served by restroom facilities. In some units, patients recover in individual rooms, whereas in others, patients recover in separate “bays” within a larger recovery room.
The administrative area should accommodate all reception, scheduling, filing and record-keeping, and billing/insurance functions. The reception area should promote face-to-face interactions between patients and staff, but also accommodate private conversations regarding sensitive matters. Adequate, well-marked toilet facilities must be nearby. Many waiting rooms include artwork, wi-fi access, telephones, television monitors, water coolers, reading materials, or music. Computer- and telephone-equipped staff workstations should be available. Staff foot traffic should move unimpeded. Cabinets for patient record storage should be adequate, although the transition to electronic records may diminish this requirement. Depending on the characteristics of the practice, an on-site billing area may be included.
The modern video colonoscope combines state-of-the-art electronic imaging technology and sophisticated mechanical engineering. Its fragile components—glass illumination fibers, angulation cables, and suction and air/water channels—are packed within a water-tight tube that is 130–168 cm in length but only 9–13 mm in diameter. The column must be strong enough to permit the endoscopist to push it through the 1.8-m-long colon, flexible enough to bend around the sharp turns, and elastic enough to return to a straight shape when the scope is pulled back. It must transmit the hand actions of the endoscopist from the proximal shaft down to the tip. The scope must be sturdy enough to withstand the repetitive and diverse stresses that occur during thousands of procedures and cleaning cycles, yet delicate enough to provide impeccable tip control and visualization.
The scope is divided into several sections (Fig 1.3). The long connector tube that runs from the scope head to the light source is called the “universal cord.” The universal cord is plugged into the light source, which also has connections to the video processor, the suction, and the air/water supplies. The head of the instrument contains endoscopist-operated switches and valves that control many scope functions. The “insertion tube” is the long, straight tube that intubates the colon. At the distal end of the insertion tube is a 10-cm bending section, which is controlled by the angulation wires using two control wheels. The variable stiffness control, if present, is located at the junction where the control section meets the insertion tube. The distal scope tip contains the channel openings, the air–water nozzle that allows insufflation and lens cleaning, the objective lens, and the light guide lens. The charge-coupled device (CCD) is a small chip (camera) that is located just behind the objective lens and that electronically captures the images and transmits them through electrical wires to the video processor (Fig 1.4). The control section contains: the angulation dials and locks for up/down and right/left tip deflection; the air–water and suction valves; and the remote switches that control photography, illumination light type (e.g. white light versus narrow band), and zoom.
Fig 1.3 The design and parts of a typical video colonoscope.
Fig 1.4 The distal tip of a colonoscope.
Although the control section has the greatest visible complexity, the insertion tube is a marvel of modern engineering (Fig 1.5). The insertion tube must carry: three hollow tubes (channels) for suction/biopsy, air and water (to wash the lens), and water (for the forward-directed jet); four angulation cables, positioned at 3, 6, 9 and 12 o’clock, which connect the right/left and up/down controls to the distal bending section of the instrument; the variable-stiffness cable; the fine electrical wires that carry the signals from the CCD to the image processor; the fiber-optic bundles—containing thousands of hairlike, 30-μm-wide, glass fibers—which transmit the light from the xenon lamp to the distal end of the instrument; the outer casings of metal that provide the scope with its mechanical properties; and the polymeric outer casing, which is smooth, durable, biocompatible, and watertight. The insertion tube must responsively transmit torque from the external shaft of the instrument, through the bends in the colon, to the instrument’s tip. Mechanically, this is accomplished by oppositely spiraled flat metal bands that run the length of the instrument. These bands are arranged so that a twist of the scope in one direction will tighten one set of bands and maintain torque integrity, whereas a twist in the opposite direction will tighten the other spiral bands. The stiffness of the insertion tube is determined principally by the formulation of the outer polymeric layer and an outer wire mesh.
Fig 1.5 Internal cutaway view of a colonoscope shaft.
The distal 40 cm of the insertion tube is more flexible than the proximal portion. This allows the distal segment to snake around the convolutions of the colon without the proximal portion forming loops. Some instruments have a variable stiffness capability activated by a ring on the proximal end of the insertion tube. Rotation of the ring pulls a wire and adds rigidity to the insertion tube. The tip deflection capability of most colonoscopes is 180° up/down and 160° right/left. The angle of view of most scopes is 140°, although one manufacturer has recently introduced a scope that has a 170° viewing angle. Most modern video colonoscopes contain “high-resolution” optics that can distinguish two lines or points that are located only fractions of a millimeter apart. The image resolution increases as the scope tip moves closer to the mucosal surface, until a critical distance is reached (<1 cm) when focus is no longer achieved and the image degrades. Modern instruments also offer “high-definition” image sensors, which can feed to densely pixilated monitors.
Mucosal imaging can be further enhanced with magnification or with alteration of the light that is delivered to the mucosal surface. The electronic magnification feature on most commercially available scopes simply enlarges the image, sacrificing the outer portion of the image, without increasing resolution. True optical zoom technology increases resolution, but is not widely commercialized. The white light typically used for illumination can also be selectively filtered. In narrow band imaging (NBI), filters transmit wavelengths of light that are highly absorbed by hemoglobin, thus producing a brownish color to the surface with intensity related to mucosal blood flow. Some manufacturers use image-processing technology to “bring out” characteristics and contrasts in the image after it has been acquired.
The endoscopy unit must stock a variety of accessories, including snares, forceps, retrieval devices, clips, and injector needles. The unit must stock an adequate inventory and a variety of devices needed to solve the commonly encountered colonoscopic predicaments. Many accessories are available in disposable and reusable versions. The disposable variety increases the up-front cost, but saves labor (no reprocessing and reassembly required) and ensures case-to-case sterility. Reusable devices must be sturdy enough for repeated use and sterilization cycles. Reusable snares require disassembly for cleaning. Most accessories are available from a variety of manufacturers, with small differences in engineering and cost.
The polypectomy snare consists of a thin wire loop attached by a long connector wire to the control handle. The wire is enclosed within a 7-French plastic sheath, which is passed through the working channel of the scope. The wire loop is opened and closed by the endoscopy assistant, using the control handle. The snare handle connects to an electrosurgical unit, and the connector wire conducts electrical current to the loop. Although bipolar snares have been developed (one wire positive and the other negative), most snares are monopolar, requiring a remote return electrode (grounding pad) to complete the electrical circuit.
The wire loop is typically fashioned from braided stainless steel wire, which combines favorable strength, configurational memory, and electrical conductance. Stiffer monofilament wires promote transection over coagulation. The loop configuration is usually oval or elliptical, although “D” and hexagonal shapes are available (Fig 1.6). Rotatable snares and combination injector/snares are available but are not essential. Some colonoscopists believe that tiny wire protrusions (barbs) on the wire snare loop facilitate flat polyp capture. The large loop snares are 5 × 3 cm, whereas the “mini-loop” is 3 × 1 cm. As most polyps are less than 1 cm in diameter, the smaller loop is adequate for most polypectomies.
Fig 1.6 Polypectomy snares. Snares differ in loop diameter, shape, and filament diameter. After it is embedded in the mucosa, the pointed tip can act as a fulcrum.
A resected polyp can usually be retrieved from the lumen by suctioning it through the working channel into a specimen trap, or by grasping it within the snare loop and pulling out the scope. Most metal grasper-type retrieval devices can only capture one or two fragments of a resected polyp. The synthetic fiber mesh baskets (such as the “Roth Net” or “Spider Net”) function like a butterfly net, and can collect multiple pieces of tissue during one pass; they are useful for retrieving multiple fragments of a large polyp after a piecemeal resection in the proximal colon (Fig 1.7a,b).
Fig 1.7 (a) Use of retrieval net. The net is placed above the fragments and closed. (b) Fragments are captured, and the assembly is withdrawn out of the colon.
Several types of specimen traps are available (Figs 1.8 and 1.9). The single bucket type is best for obtaining a fluid/stool for microbiology; it is adequate for polyp entrapment, but can overflow, causing the polyp to travel into the main suction canister (Fig 1.10). The single chamber, filter type cannot overflow, but cannot collect fluid for microbiology (Fig 1.11). The four chamber type allows polyps from several locations to be caught within one device, but can cause confusion if the site of each polyp is not carefully recorded (Fig 1.8).
Fig 1.8 Polyp retrieval trap. A compartmented trap permits capture of polyp from different areas of the colon. Even samples taken by biopsy forceps will be caught within the small grid that collects polyps.
Fig 1.9 Using simple mesh to retrieve polyp specimens. A mesh pad can be inserted between the suction port on the scope and the suction tubing. This will function as a filter, trapping a resected specimen when it is suctioned through the system.
Fig 1.10 The canister-type traps can overflow. This can cause a polyp to be lost (c).
Fig 1.11 Simple filter-type specimen trap. Unlike the canister-type traps, this device cannot overflow with fluid, causing specimen to be lost. However, fluid/stool cannot be captured for microbiological analysis.
Biopsy forceps are discussed in Chapter 8.
During colonoscopy, there are multiple indications for tissue injection, including elevation of sessile polyps, hemostasis, and tattooing. Injection is accomplished using disposable metal injection needles. These needles have a stiff outer sheath of 2.3–2.8 mm diameter, with a smaller inner channel for fluid passage. The tip of the needle is beveled and the needle size is 21–25 G. The needles are retractable, and must be passed through the working channel in the retracted position in order to avoid an expensive puncture injury to the scope. The needles can be locked in their extended position during introduction of the tip into target tissue. Fluid is pushed from a syringe connected to the sheath. In general, if the tiny needle punctures the full thickness of the colon wall, there is no untoward effect.
When fluid is pushed through a spray catheter, it is dispersed through multiple fine apertures in the metal nozzle at the catheter’s tip, producing a fine mist in a 360° arc. The technique is useful for chromoendoscopy, because it can cover the mucosal surface efficiently and relatively evenly. Spray catheters may be disposable or reusable.
Clipping devices contain two stainless steel, detachable, tweezer-like prongs that are attached by a long delivery catheter to an external control handle. Clips can be used to close a polypectomy site, seal a perforation, mark a lesion (they are radiopaque, and are palpable by a surgeon), clamp a bleeding vessel, or anchor a decompression tube. Numerous clips can be placed on a lesion. Clips can be deployed with the colonoscope in the retroflexed position. Most clip applicators are for single use. Some are applied and fired without the ability to reposition the device, whereas others may be repeatedly opened and closed. Some devices are rotatable, which may help achieve a favorable orientation. The outer plastic sheath is the same diameter as a snare sheath. Once fired, the clip remains attached to the target tissue for 2–4 weeks, after which it sloughs.
These plastic, non-conductive loops close like a noose around a polyp pedicle and strangulate the large blood vessels that course through the stalk. Their main use is for prevention of bleeding when removing a large pedunculated polyp, but they can also be applied to a bleeding pedicle after polypectomy. Once positioned, the loop is tightened, and then locked shut with a plastic collar controlled by an external handle. In practice, these ligatures have a limited role, partly because the loop has little tensile strength and can become enmeshed in the head of a polyp during attempts to encircle the stalk.
Thermal devices are discussed in Chapter 9.
Affixed to the tip of the colonoscope and extending several millimeters beyond the faceplate, these clear plastic cylinders are designed to enhance visualization of the valleys between the haustral folds (Fig 1.12). Several reports suggest that they may increase detection of small polyps, with no decrease in the maneuverability of the scope. A special cap may be used during endoscopic mucosal resection, in a method analogous to variceal banding. Here the mucosal target is suctioned into the cap, and then a snare seated in a small ridge at the tip of the device is closed around the tissue.
Fig 1.12 Plastic transparent cap. This may be attached to the end of an endoscope and enhance observation behind folds as the instrument is withdrawn through the colon. (From Colonoscopy: Principles and Practice, 2nd edition.)
Overtubes slide over the scope after it has been straightened in the sigmoid and restrict loop formation and facilitate advancement of the instrument. Overtubes should not be used to straighten a loop, as it may damage the colon wall. Overtubes must be placed on the colonoscope before it is inserted into the colon, effectively shortening the instrument until they are deployed. Originally, overtubes were inserted under fluoroscopic control to ensure that the scope was straight, but “feel” may also be relied upon to deploy this device. With enhancements in scope engineering, overtubes are not commonly used today.
The modern endoscopy suite should promote safety, efficiency, hygiene, and comfort. Electronic procedure reporting represents an important advance. Careful attention to practice characteristics during the planning phase is essential. The scope is a platform for numerous diagnostic and therapeutic procedures. Improvements in optics and mechanical engineering have enhanced all clinical functions, and further improvements are forthcoming. Multiple accessories are available that support colonoscopic practice.
Further reading
1. Barlow DE. The video colonoscope. In: Waye JD, Rex DK, Williams CB, editors. Colonoscopy: Principles and Practice. 2nd ed. Chichester: Wiley-Blackwell; 2009.
2. Croffie J, Carpenter S, Chuttani R, et al. ASGE Technology Status Evaluation Report: disposable endoscopic accessories. Gastrointest Endosc 2005;62:477–9.
3. Kaltenbach T, Watson R, Shah J, et al. Colonoscopy with clipping is useful in the diagnosis and treatment of diverticular bleeding. Clin Gastroenterol Hepatol 2012;10:131–7. Epub 2011 Nov 2.
4. Luigiano C, Ferrara F, Ghersi S, et al. Endoclip-assisted resection of large pedunculated colorectal polyps: technical aspects and outcome. Dig Dis Sci 2010;55:1726–31. Epub 2009 Aug 6.
5. Marasco JA, Marasco RF. Designing the ambulatory endoscopy center. Gastrointest Endosc Clin N Am 2002;12:185–204, v.
6. Pike IM. Outpatient endoscopy possibilities for the office. Gastrointest Endosc Clin N Am 2002;12:245–58.
7. Schembre DB, Ross AS, Gluck MN, Brandabur JJ, McCormick SE, Lin OS. Spiral overtube-assisted colonoscopy after incomplete colonoscopy in the redundant colon. Gastrointest Endosc 2011;73:515–9.
8. Technology Assessment Committe, Barkun A, Liu J, et al. Update on endoscopic tissue sampling devices. Gastrointest Endosc 2006;63:741–5.
9. Technology Assessment Committee, Chuttani R, Barkun A, et al. Endoscopic clip application devices. Gastrointest Endosc 2006;63:746–50.
10. de Wijkerslooth TR, Stoop EM, Bossuyt PM, et al. Adenoma detection with cap-assisted colonoscopy versus regular colonoscopy: a randomised controlled trial. Gut 2012;61:1426–34. Epub 2011 Dec 20.
11. Waye JD, Rex DK, Williams CB, editors. Colonoscopy: Principles and Practice. 2nd ed. Chichester: Wiley-Blackwell; 2009.
CHAPTER 2
The Role of the Endoscopy Assistant during Colonoscopy
A well-trained endoscopy assistant is crucial to a successful colonoscopy. By providing an additional set of eyes and hands, anticipating the next step in the procedure, and understanding the preferences of the endoscopist, the assistant enhances the efficiency and thoroughness of the procedure, and the safety and comfort of the patient. Perhaps most importantly, the assistant creates an atmosphere that is reassuring to the patient, family, and endoscopist.
Different professional societies provide varying recommendations. The certification of endoscopy assistants reflects the requirements of the hospital, ambulatory endoscopy center, or medical office employing the assistant. In addition, the assistant’s training reflects the requirements of national accrediting agencies. Regardless of certification and educational level, proper training of endoscopic assistants is essential. Training may be acquired through didactic courses, written materials, formal testing, or an apprenticeship with observation of procedures. The skills required of an endoscopy assistant are highly specialized and not taught in most general nursing or medical technician educational programs. One reasonable approach is to provide a new recruit with a minimum of a 2-week training period to study didactic materials and observe procedures. After this, a graduated introduction into participation during the procedures is begun, with experienced personnel available to observe, to mentor, and to step in when challenging situations arise. Continuing education programs and competency evaluation should be required of all endoscopic assistants, regardless of seniority.
The endoscopy assistant should wear personal protective equipment. This universally includes gloves, which should be well-fitting, as well as surgical scrubs or a gown. In some cases, a protective mask and/or protective eyewear may be appropriate.