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Editors: Jerome Waye, Christopher Williams & Douglas Rex

1. Colonoscopy overview

Jerome D. Waye, Douglas K. Rex & Christopher B. Williams

The development of flexible colonoscopy followed the introduction of the flexible gastroscope by a few years. The ability to look into the colon extended the view from the rigid sigmoidoscope throughout the entire large bowel.

In the beginning, it was thought that colonoscopy would not be possible by pushing an instrument through the length of the colon from an external position outside the anus. Original attempts at colonic intubation were aided by pulling backward on a swallowed long string that passed through the entire intestinal tract to which a gastroscope was tied. Attempts were also made at positioning the flexible colonoscope through a rigid sigmoidoscope, but none of the methods were accepted.

Dr Bergin Overholt made a latex cast of the sigmoid colon using a rapidly solidifying latex enema in order to understand the convoluted course of the sigmoid colon, and did the first colonoscopy.

Improvements in technology and technical skill advanced the capability of examining further and further into the large bowel, with the early attempts aided by fluoroscopic examination of the abdomen during instrumentation procedures.

A better understanding of intraluminal anatomy led to the discontinuation of reliance on fluoroscopy, and with advances in technique, colonoscopy rapidly became the preferred imaging modality for the large bowel, displacing almost completely the barium enema.

The indications for colonoscopy are myriad, while screening and cancer prevention are becoming the most frequent indication for this examination.

Prior to the development of flexible endoscopy, when a gastroenterologist visualized a polyp on rigid sigmoidoscopy, they would call a surgeon to remove the polyp. Gastroenterologists were not trained in the removal of polyps, although surgeons, even in their residency training, were adept at polypectomy. It was natural therefore for a surgeon to develop techniques of polypectomy through the flexible colonoscope.

The first application of colonoscopic polypectomy was introduced by Dr Hiromi Shinya in New York City using a home-made wire passed through a thin plastic catheter. An assistant hand-held the connection between the active cord of an electrosurgical unit and a hemostat clamped on the wire after the polyp was encircled. Over the next few years, rapid developments occurred so that polypectomy is now a standard therapeutic application in the large bowel.

Almost all polyps can be removed, and submucosal injections of various solutions have made resection of large polyps easier and safer. There is little controversy about the indications for and against the need for surgery when a polyp contains invasive cancer, and these concepts have become well accepted over the past several years. The role for colonoscopy in lower GI bleeding and in inflammatory bowel disease has evolved largely due to the work of investigators in these fields who have written these chapters.

Colonoscopy is now a discipline that is neither a medical or surgical tool, but addresses a broad range of medicine including internal medicine, gastroenterology, surgery, pathology, radiology, pediatrics, and molecular biology. The future will see other developments in instrumentation, techniques, and applications. The chapters reproduced in this e-book are representative of the textbook Colonoscopy: Principles and Practice published by Blackwell Publishing, Ltd, in 2004 with 54 chapters edited by Jerome D. Waye, Douglas K. Rex, and Christopher B. Williams.

Copyright © Blackwell Publishing, 2004

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Classification of indications
  Diagnostic vs. therapeutic
  High-risk vs. low-risk
  High-yield vs. low-yield
Alternatives to colonoscopy
Specific indications
   Colonoscopic treatment of bleeding
  Abdominal pain and constipation
  Chronic diarrhea
  Abnormal radiographs or sigmoidoscopy
  Established ulcerative colitis
   Surveillance in ulcerative colitis
  Established Crohn's disease
  Surveillance after colonoscopic polypectomy
  Surveillance after cancer resection
   Timing of surveillance
   Rectal cancer
  Screening average risk subjects
  Miscellaneous indications
Contraindications to colonoscopy
  Absolute contraindications
  Relative contraindications
  Higher risk subjects
  Average-risk subjects
Rationale for screening
  Fecal occult blood test (FOBT)
  Flexible sigmoidoscopy
   Limitations of screening by flexible sigmoidoscopy
  Combined flexible sigmoidoscopy and FOBT
  Radiographic colon imaging with barium, CT, or MRI
  The potential for genetic testing
The case for screening with colonoscopy
  Arguments against screening with colonoscopy
  Arguments for screening with colonoscopy
   Does screening colonoscopy reduce mortality?
  Patient acceptance of colonoscopy screening
  Potential harm from colonoscopy
  Resources for screening colonoscopy
Costs of screening for colon cancer
Screening colonoscopy: areas of uncertainty
  Reducing overall mortality?
  Timing of colonoscopy screening
   When to repeat screening?
  Will screening colonoscopy be superseded?
Factors suggesting difficulty in polypectomy
  Polyp size
  Malignant potential
   More than one-third of the circumference
   Polyps crossing two haustral septae
   Polyps involving the appendiceal orifice
  Bleeding risk
Practice issues for difficult polyps
  Risks and consent
  Ambulatory or in-patient polypectomy
  Which colonoscope for difficult polyps?
  Sometimes a thinner endoscope is helpful
  Which snare?
   Types of snares
   Use of the mini snare
  Submucosal injection for polypectomy (SIP)
   Injection fluid
   Injection site
   Polyps behind folds
   Injection volume
   The non-lifting sign
   Tumor tracking
  Cap assisted polypectomy
Polyp resection technique
  Stop at the line
  Piecemeal polypectomy
  Positioning the polyp
  Clamshell polyps
  Flat polyps
  Residual fragments of adenoma after polypectomy
Judging and marking the location of lesion
  Location by depth of insertion
  Endoscopic landmarks
  Marker injections into the colon wall
   Indocyanine green
   India ink
  Intraoperative colonoscopy
  Radiological methods of localization
   Barium enema
   Magnetic imaging
The extremely difficult colonoscopy
  Definition of malignancy and polyps
  Assessment of polyps
Risk factors for malignant polyps
  Polyp size and villous component
   Polyp size
  Flat lesions
   Are flat lesions missed in the West?
Initial endoscopic evaluation and treatment of polyps
  Visual assessment
  Difficulties after resection
  Localization of polyps, tattooing
Surgery or endoscopic follow-up?
  Pedunculated adenomas
   Factors suggesting no need for surgery
   Factors favoring surgery after polypectomy
   What is a safe margin?
  Sessile adenomas
Role of the clinician
  Follow-up protocols
  Balancing the risk of surgery
  Rectal lesions
  Patients with family history
  The spectrum of nonpolypoid lesions and their morphogenesis
  Endoscopic criteria
  Pathological criteria
The epidemiology of flat and depressed lesions in the West
  United Kingdom
  North America
The biological and clinical significance of flat lesions
  Flat lesions or really just small polyps?
   Nomenclature issue
   USA national polyp study
   Flat lesions are different
  Association of flat lesions with advanced pathology
  Depressed lesions are more important than simple flat lesions
  'De novo' colorectal cancer and the relationship between early cancer and F & D lesions
  Differences in genetic and biological markers between flat and polypoid lesions
  Colorectal carcinogenesis and F & D lesions
   A different genetic pathway?
The challenge of endoscopic detection of F & D lesions
Conclusion and clinical approach
Resuscitation and initial evaluation
  History and physical examination
  Medication history
Diagnostic evaluation
  Gastric lavage/aspiration
Bowel preparation
Endoscopes and other equipment
  Hemostatic accessories
  Tissue marking
  Coagulation probes
Study results
  Patients admitted for hematochezia
Specific lesions
  Diverticular hemorrhage
   Comparing surgery with colonoscopic treatment
  Internal hemorrhoids
   Treatment of severe hemorrhoidal bleeding
  Ischemic colitis
   Clinical presentation
   Diagnosing ischemic colitis
   Treatment for ischemic colitis
  Solitary rectal ulcer syndrome
   Colonoscopic therapy
  Postpolypectomy hemorrhage (delayed)
   Incidence of postpolypectomy hemorrhage
   Colonoscopy findings
   Treatment for postpolypectomy hemorrhage
  Colonic angiomas
   Bicap or heater probe study in treatment of bleeding angiomas
   Findings at colonoscopy
   Techniques for hemostasis
Characteristic endoscopic findings in inflammatory bowel disease
  Crohn's disease
  Aphthous ulcer
   Ulcers and cobblestoning
   Strictures and fistulae
   Vascular pattern
   Upper GI involvement
  Ulcerative colitis
   Endoscopic appearances
  Differentiation between Crohn's disease, ulcerative colitis, and indeterminate colitis(Fig. 12)
Endoscopic assessment of extent and severity of inflammatory bowel disease
Endoscopic monitoring of therapeutic efficacy and its value in clinical trials
Perioperative endoscopy in Crohn's disease
Endoscopic features of the ileoanal pouch and pouchitis
Endoscopic treatment of Crohn's disease complications
Conclusion: the role of endoscopy in IBD(Fig. 14)
Indications for colonoscopy
When diagnostic colonoscopy is not indicated
Preparation of the patient for colonoscopy
  Antibiotic prophylaxis
  Bowel preparation
   Purge methods
   Lavage methods
  Technique of colonoscopy
  Risks and complications of colonoscopy
Indications for colonoscopy
  Rectal bleeding in children
  Chronic diarrhea
  Inflammatory bowel disease, colitis, and cancer
  Therapeutic colonoscopy
Suggested reading
Aids to advancing a colonoscope
  Internal spines
  Mother-and-baby colonoscope systems
  Thread-guided pull endoscopy ('rope-way' colonoscopy and enteroscopy)
Friction reduction
  Lubricating the endoscope
  Vibrating the shaft of the endoscope
  Everting toposcopic endoscopy
Novel propulsion systems
  Balloons to grip the wall—Earthworm
   Potential damage to the colon wall
  Suction crawler—Limpet or starfish
  Serpentine robot—Snake
  Many legs—Millipede
  Few legs—Lizard and ant
  Water jet—Octopus
  Wheels and belts
Wireless capsule colonoscopy
Future needs in other areas related to colonoscopy
  Bowel preparation
  Instrument disinfection
  New imaging methods
The future of therapeutic colonoscopy

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