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Colonoscopy


Goals/Objectives

  • Basic Principles

  • Anatomy

  • Physiologic Considerations

  • Technical Considerations

Diagnostic Colonoscopy

Jean Marc Canard
Jean-Christophe Létard
Ian Penman

From Canard JM, et al: Gastrointestinal Endoscopy in Practice, 1st edition (Churchill Livingstone 2011)

Key Points

  • High quality colonic preparation is essential.

  • Good technique is the key to allowing a rapid, complete examination of the colon.

  • The colonoscope should be advanced under visual control.

  • The colonoscope should be shortened frequently to ensure a short, straight endoscope.

  • Abdominal palpation and patient position changes are useful adjuncts.

  • Confirmation that the cecum has been reached should be made by identifying the ileocecal valve, appendix or entering the ileum and visualizing the small bowel.

  • Withdrawing the colonoscope should take a minimum of 6 minutes.

  • Retroflex gently in the rectum to avoid missing distal lesions.

  • Audit of colonoscopy outcomes should be performed regularly.

Introduction

Optical colonoscopy is the gold standard method for examining the colon, is widely available, and offers the potential for biopsy and/or therapy during the same procedure. It is commonly performed for the evaluation of patients with lower GI symptoms and for screening/surveillance in people at risk of colorectal cancer. While colonoscopy has been an established technique for over 30 years, it can be technically difficult and is associated with a small but real risk of major complications. For these reasons, a good, careful technique, combined with a sound knowledge of polypectomy procedures is essential.

Anatomy

The colon is an elastic tube that extends from the rectum to the ileocecal valve and whose normal mucosa is pale pink in color. The submucosal vascular network is visible, as are the rather large submucosal veins.

The colon comprises mobile segments ( Figure 39-1-1 ) (cecum, transverse colon, sigmoid colon) whose length depends on the size of the mesocolon, which attaches these segments to the posterior abdominal wall and the fixed segments (ascending colon, hepatic flexure, descending colon, rectum). The splenic flexure is partially attached by the phrenocolic ligament, the length and rigidity of which enable it to descend and become rounded on insertion of a colonoscope.

F igure 39-1-1, Mobile colonic segments: cecum; transverse colon; sigmoid colon.

However, there are numerous anatomic variations resulting from the absence of mesorectal stickiness during gestation, which in turn induces variable mobility in the ascending and descending colon. In some cases, the cecum is incompletely rotated (cecum recurvatum).

The rectum is 12–15 cm long beginning from the anal margin. It is the shape of an elongated ampulla and is segmented by three or four mucosal folds (valves of Houston). The sigmoid varies in length, depending on the length of its mesocolon. The colonic lumen and haustrations in the descending or sigmoid colon are generally circular ( Figure 39-1-2 ). The splenic flexure exhibits a blue area that is attributable to the impression of the spleen. The lumen of the transverse colon is triangular ( Figure 39-1-3 ).

F igure 39-1-2, Circular haustrations in the descending and sigmoid colon.

F igure 39-1-3, Triangular haustrations in the transverse colon.

The indentation of the liver at the hepatic flexure can be recognized by its bluish color but note that this may also be visible from the descending colon or in the middle of the transverse colon. The hepatic flexure is easily confused with the cecal pole (one of the lips of the ileocecal valve may be confused with the thickened fold viewed tangentially above a flexure). The only reliable reference points are the terminal ileum, ileocecal valve and the appendicular orifice.

The internal aspect of the cecal pole, which typically exhibits a “crow’s foot” shape, is the point of convergence of the three longitudinal bands of colonic muscle that extend to the appendicular orifice, which generally takes the form of a very narrow slit. An operated appendix looks the same, except that the stump has been buried and may resemble a polyp (can be biopsied but not resected).

The ileocecal valve is 5 cm above the cecal pole, on the medial wall of the right colon, usually on the left side of the colonoscopic field of vision. The valve takes the form of a transversally elongated mouth and is generally situated on the margin of one of the crow's foot folds. The orifice of the ileocecal valve can rarely be viewed right away as it is normally located on the upper lip. Once the lower and upper lips of the ileocecal valve have been identified, it is possible to enter its orifice and examine the terminal ileum, where the submucosal vascular network is far more visible than in the colon. In children and adolescents, Peyer's patches are often observed in the terminal ileum, where they constitute 2–3 mm white or translucent sessile protrusions, and villi are also seen.

Postoperative Colonic Anatomy

The most prevalent types of colonic surgery are left hemicolectomy (anastomosis between the rectum and transverse colon), right hemicolectomy (anastomosis between the small intestine and transverse colon), subtotal colectomy (anastomosis between the ileum and rectum), and total colectomy with ileo-anal anastomosis. Anastomoses involving the small intestine, colon or rectum can either be end-to-side or end-to-end. Hence, it is necessary to be able to recognize the cul-de-sac and withdraw the endoscope in order to progress in the right direction. In cases of colostomy, colonoscopy can be performed via the stoma.

Indications for Colonoscopy (TC)

These are general indications but specific guidelines exist in many countries and may vary. Readers should be familiar with the guidelines of the country in which they are practicing. The following are the guidelines from the Société Française d'Endoscopie Digestive (SFED).

Patients at Average Risk of Colorectal Cancer (CRC) *

* Defined as the average population risk.

  • Asymptomatic patients with a positive occult blood test (performed as part of a screening program, not on an individual basis)

  • Patients with abdominal pain associated with a change in bowel habit to looser for >6 weeks

    • Over the age of 50

    • Under the age of 50, if there is no response to symptomatic treatment

  • Patients with overt rectal bleeding

    • Repeated episodes of dark red bleeding, irrespective of age

    • Repeated isolated episodes of bright red bleeding in patients over 50 (flexible sigmoidoscopy or TC in patients under 50)

    • Profuse bleeding, as soon as the patient's condition allows

  • Patients with symptomatic diverticulosis

  • TC is contraindicated in suspected acute diverticulitis, but should be undertaken at a later date (~6 weeks) if surgery is being considered or the diagnosis is in doubt

  • Patients with endocarditis caused by Streptococcus bovis or group D streptococci.

Surveillance of Asymptomatic Patients at High Risk of CRC

  • Patients with a family history of CRC with a 1st-degree relative under 60 or several 1st-degree relatives with CRC:

    • TC at age 45 or 5 years younger than the age at diagnosis of the index case; if he/she was under 50 then TC at 5 and 10 years

    • For adenoma including non-advanced forms: follow-up colonoscopy at 3 years

  • Family history of colonic adenoma in a 1st-degree relative under 60:

    • TC at the age of 45 or 5 years younger than the age at diagnosis of the index case; if he/she was under 50, then TC at 5 and 10 years.

  • After surgery for colorectal cancer:

    • Incomplete colonic examination before surgery: TC at 6 months

    • Complete colonic examination before surgery: TC at 2–3 years then at 7–8 years

  • Patients with acromegaly:

    • At diagnosis, then depending on the findings. If normal, every 5 years until biochemical evidence of ‘cure’.

Surveillance of Asymptomatic Patients at Very High Risk of CRC

  • FAP (familial adenomatous polyposis)

    • Member of a family with FAP: flexible sigmoidoscopy annually from the age 10–12 years

    • Member of a family with attenuated FAP: TC annually from the age of 30

    • FAP after colectomy: flexible sigmoidoscopy annually.

  • Hereditary non-polyposis colon cancer (HNPCC)

    • Member of a family with HNPCC: TC every other year from the age of 20–25

    • HNPCC after surgery: TC every other year

  • Juvenile polyposis (JP) family member: TC every 2–3 years from the age of 10–15

  • Peutz–Jeghers syndrome family member: TC every 2–3 years from the age of 18

  • Inflammatory bowel disease: pancolitis (> 10 years) or left-side colitis (> 15 years): TC every 2 (pancolitis) to 3 years (left-side colitis) and biopsies every 10 cm. Recent studies recommend routine use of indigo carmine or methylene blue chromoendoscopy with fewer, targeted biopsies of subtle abnormalities of colonic crypts or vessel pattern.

Surveillance of Patients After Resection of One or More Colonic Polyps

  • Hyperplastic polyps (size ≥1 cm, ≥5 in number, location in the proximal colon with a family history of hyperplastic polyposis): TC at 5, and 15 years

  • Low-risk adenomas (V3) or advanced adenomas (size ≥1 cm, ≥25% villous component, high-grade dysplasia (HGD) or in situ carcinoma) or V4.1/V4.2 adenomas:

    • Incomplete resection: TC at 3 months

    • Complete resection: advanced adenoma or ≥3 in number, or a family history of CRC; TC at 3, 8, 13, and 23 years

    • Complete resection: non-advanced adenoma, <3 in number and no family history of CRC; TC at 5, 10, and 20 years

  • Malignancy in an adenoma (V4.3, V4.4, V5, “polyp-cancers”)

    • Incomplete resection (V4.3, V4.4): TC at 3 months then at 3 years if nothing at 3 months

    • Complete resection (V4.3/4.4): TC at 3 years

    • Complete resection (V5): TC at 3 months if patient does not undergo colectomy.

Box 39-1-1
Amsterdam II Criteria for HNPCC

  • Three or more relatives with HNPCC associated cancers (colorectal cancer, endometrial cancer, small bowel, ureter, or renal pelvis), one of whom is a 1st-degree relative to the other two.

  • At least two generations must be affected.

  • One individual from the family must have been diagnosed with one or more cancers before the age of 50.

  • FAP must be excluded.

Box 39-1-2
Vienna Classification of Gastrointestinal Epithelial Neoplasia and Superficial Gastrointestinal Cancers

  • Category V1: negative for neoplasia.

  • Category V2: indefinite for neoplasia.

  • Category V3: low-grade neoplasia (LGIN).

  • Category V4: high-grade neoplasia (HGIN).

    • V4.1: high-grade dysplasia.

    • V4.2: in situ (non-invasive) carcinoma.

    • V4.3: suspicious for invasive carcinoma.

    • V4.4: intramucosal carcinoma.

  • Category V5: submucosal invasion by carcinoma.

Contraindications

  • Colonic perforation

  • Peritonitis

  • Acute cardiorespiratory failure

  • Recent myocardial infarction

  • Recent colonic surgery

  • Major aneurysm of the abdominal aorta or its branches.

Equipment

The standard, multipurpose colonoscope used routinely measures 130 cm in length. The long colonoscope (170 cm) is more fragile, more expensive and less practical. Flexible sigmoidoscopes (60 cm long) are also available but are less useful, except in young adults with bright red rectal bleeding, or bloody diarrhea.

The more flexible pediatric colonoscope (130 cm long, 11 mm in diameter) is used in children from the age of 2 years upwards. It may be useful in adults for passing through strictures or in patients with a narrow, tortuous or acutely angulated sigmoid colon.

The following accessories are required: cold biopsy forceps, hot biopsy forceps, foreign body forceps, tripod grasper forceps, polypectomy snares, lavage catheter, injection needles, endoscopic clips, detachable loops dilating balloons, polyp retrieval (‘Roth’) nets, fixative containers.

Preparation of the Examination Room ( Box 39-1-3 )

Setting Up and Testing Endoscopes

  • Set up the video colonoscope on the console

  • Check that the colonoscope is working properly (angulation, aspiration, insufflation, clear image)

  • Check the connections with the monitor, the printer and the image capturing equipment

  • Test the white balance for any endoscopes that still require this function

  • Check the image storage equipment, computer switched on, patient data entered.

Setting Up and Testing Additional Equipment

  • Suction bottle and connections: (single use disposable)

  • Examination couch: correctly insulated with a disposable protective covering and cot sides to prevent falls

  • Instrument trolley with labeled drawers or tiers containing all the instruments. It must be carefully checked before each examination and should match the type of examination

  • Accessories

  • Dyes and tattoos: to detect, delineate and mark small mucosal lesions (flat polyps, etc.)

    • 0.2% indigo carmine. It should be ready for use in a 50 mL syringe; colitis surveillance requires 150–200 mL, so it is useful to make it up in a bag of 0.9% saline

    • 0.5 or 0.7% methylene blue

    • Pure carbon black (“Spot”, GI Supply Inc., Camp Hill, PA, USA) can be used to mark the site of a lesion before surgery, or for marking where a polyp was removed so that the area can easily be identified during subsequent screening colonoscopy. Sterile India ink suspension is an alternative but has been associated with immunological reactions

  • Anti-foaming agent (simethicone)

  • Lavage catheter

  • Disposable gloves

  • Gauze swabs

  • Lubricant for rectal examination and for lubricating the colonoscope

  • Washing equipment: sterile water, 50 mL syringes, connector tubing, and power wash pump.

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