Colonoscopy refers to the endoscopic examination of the entire colon and rectum and often includes the terminal ileum. Common activities performed during colonoscopy include inspection, biopsy, photography, and video recording. The procedure is technically challenging and requires considerable training and experience. High-quality examinations require good clinical judgment, anatomy and pathology recognition, technical skill in manipulating the scope and performing biopsies, appropriate patient monitoring, and well-maintained and cleaned equipment to ensure patient safety. Video colonoscopes enable complete examinations of the entire colon in more than 95% of examinations.
Most colorectal cancers appear to develop from benign neoplastic (adenomatous) lesions. Americans of average risk have a 6% lifetime risk of developing colon cancer. Adenomas occur in about 30% of individuals at age 50 and 55% at age 80. Several screening modalities are advocated to detect early adenomas and cancer, including colonoscopy every 10 years after age 50. Colonoscopy has sensitivities of 75% to 85% for polyps less than 1 cm in diameter and 95% for larger polyps and cancers. The specificity for the examination approaches 100%.
A single screening colonoscopy in asymptomatic individuals at age 65 has been advocated for reducing mortality from colorectal cancer. Several analyses have suggested that a single screening or repeated screenings every 10 years after age 50 may be cost-effective strategies. Despite increased insurance coverage for colonoscopy screening, the feasibility of screening an entire population has yet to be established.
Colonoscopy is the diagnostic procedure of choice for patients with a positive fecal occult blood test (FOBT). Approximately 50% of individuals with a positive FOBT have a neoplastic lesion (adenomas, 38%; cancer, 12%) at endoscopy. Patients with long-standing ulcerative colitis should undergo colonoscopy with biopsy to examine for dysplasia beginning 8 years after the development of pancolitis or 15 years after the development of distal disease.
Colonoscopy is indicated for villous adenomas of any size that are discovered during flexible sigmoidoscopy. Distal tubular adenomas are not associated with an increase in proximal adenomas, and some clinicians do not believe that colonoscopy is required after removal of a small, distal tubular adenoma. Historically, adenomas larger than 1 cm in diameter have been referred for colonoscopy. Larger colonic lesions are more often villous or tubulovillous, necessitating
colonoscopic removal of the lesion and examination for synchronous lesions. Some studies suggest that purely tubular lesions that are larger than 1 cm in diameter can be followed without immediate colonoscopy. This strategy may be problematic, because a biopsy sample from within a large lesion may fail to recognize the most significant pathology (i.e., missed villous or cancerous elements). Despite some contrary opinions, colonoscopy is generally not indicated after the diagnosis of a hypertrophic distal polyp.
Average procedure times for experienced endoscopists are about 10 minutes to reach the cecum and 30 minutes to complete the entire procedure. Inadequate preparation is the most common reason for prolonged or incomplete examinations. Most individuals in the United States receive 3 to 4 L of a polyethylene glycol-based electrolyte solution the day before the examination. Some studies have suggested longer procedures and greater discomfort occur in women undergoing the procedure, possibly because of their anatomically longer colons and greater sigmoid mobility. Older individuals may present greater difficulty in reaching the cecum.
Colonoscopy routinely is performed after the administration of conscious sedation. Intravenous midazolam and meperidine have been the drugs most commonly employed. Unfortunately, 15% of individuals receiving these two medications are dissatisfied with their sedation. Propofol is an intravenous, short-acting sedative used for the induction of general anesthesia. Propofol may provide superior sedation and more rapid recovery, but its safety in office situations has not been demonstrated. Studies have demonstrated that the procedure can be performed in selected individuals without sedation, with relatively high (70% to 85%) rates of patients willing to undergo a similar procedure again without sedation. Many physicians feel more comfortable with routine administration of sedation to improve procedure acceptance among patients. Appendix F contains guidelines for monitoring the patient receiving conscious sedation at endoscopy.
Debate exists about the number of procedures that trainees need to perform to become competent in colonoscopy. The American Society of Gastroenterology (ASG) has historically used 200 procedures as its standard. Although primary care physicians have argued that this number is unnecessarily high and precludes well-trained primary care physicians from performance of colonoscopy, there is evidence that at least 100 to 150 procedures are needed by many learners to achieve high rates (>95%) of intubation of the cecum. Using reach-the-cecum rates and other markers of competence, less than 3% of gastrointestinal surgery fellows are graded as competent after 100 procedures.
Polypectomy is the most commonly performed therapeutic procedure performed at colonoscopy. Patients can experience considerable morbidity from bleeding or colon perforation at polypectomy. There is a strong relationship between complication rates of diagnostic and therapeutic colonoscopy and the experience of the endoscopist. The highest rates of these complications appear in the first 500 procedures.
Primary care physicians desiring to perform diagnostic screening colonoscopies may create added health care costs if they do not perform polypectomy. Because 20% to 50% of screening colonoscopies have polyps or tumors diagnosed at screening, it is argued that failure to perform polypectomy produces unnecessary referrals. Less experienced endoscopists may have two to three times the failure rate in diagnosing advanced-stage adenomatous polyps and cancers compared with experienced endoscopists. Failure to recognize pathology at colonoscopy could create harmful circumstances for patients and medicolegal issues for the clinician.
The ASGE suggests that hospital credentialing for colonoscopy should include the ability to perform associated therapeutic procedures. According to the ASGE, there are limited alternate paths for credentialing outside of completion of a full gastroenterology or gastrointestinal surgery fellowship program. However, they recommend privileges only for physicians able to achieve comparable training to a fellowship. Although family physicians may have trouble achieving adequate numbers of procedures to receive appropriate consideration for colonoscopy privileges according to ASGE guidelines, more than 1400 family physicians currently have hospital privileges to perform colonoscopy in a hospital setting. In rural areas, an average of 6% of family physicians perform the procedure.
Many primary care physicians attend short courses to receive initial training in colonoscopy. Short courses can augment technical and clinical skills, but the ASGE feels these courses cannot replace patient procedures in gaining experience. Proctored or precepted procedures should be performed until physicians can demonstrate competence in performing complete examinations, supervision of conscious sedation, and polyp removal techniques.
The patient is placed on the examination table in the left lateral position. Intravenous access is obtained, and sedation is administered (25 to 75 mg of meperidine and 2 to 8 mg of midazolam). Appropriate patient monitoring includes frequent vital signs, oximetry, and heart rhythm (electrocardiographic) evaluation throughout the procedure (see procedural illustrations 1–10 in Chapter 48). These illustrations also apply to the scope insertion and examination techniques in the rectosigmoid at colonoscopy.
(1) Intravenous access is obtained, and sedation is administered (25 to 75 mg of meperidine and 2 to 8 mg of midazolam).
Traversing the rectosigmoid junction is the one of the most difficult aspects of the procedure. Prior pelvic surgery may produce extensive adhesions in this area (see techniques to pass through this area in Chapter 48). Insert the scope only through visible lumen.
(2) Insert the scope only through visible lumen.
PITFALL: Sliding the scope along the colon wall (i.e., slide-by technique) is not advocated, because this technique may result in perforation at the rectosigmoid junction.
The wall of the descending (right) colon has a characteristic circular appearance with encircling folds (Figure 3A). A sharp turn appears at the splenic flexure. A bluish color of the vascular spleen may be visible through the colon wall. A sharp turn of the scope tip (with torquing) often is required to pass through this flexure (Figure 3B). The wall of the transverse colon has a characteristic triangular appearance (Figure 3C).
(3) The descending colon wall has a characteristic circular appearance with encircling folds, and the transverse colon wall has a characteristic triangular appearance.
The passage through the transverse colon is relatively straight. Another sharp angle exists at the hepatic flexure. The hepatic flexure can be identified by the bluish brown shadow of the liver seen through the colon wall. The examiner also may notice transillumination through the left upper abdominal wall from the endoscope light. The assistant can press down on the patient's right upper abdomen to facilitate the downward deflection of the scope tip into the ascending (left) colon. The ascending colon has a characteristic pattern of mucosal folds that do not encircle the lumen completely.
(4) To facilitate the downward deflection of the scope tip into the ascending color, have an assistant press down on the patient's right upper abdomen.
PITFALL: Avoid creation of loops within the colon, which can increase discomfort and risk of complications. Keep the instrument as straight (short) as possible. Repeated short insertions and withdrawals and aspiration of air at the flexures can pleat the colon wall onto the instrument. Abdominal pressure by the assistant can eliminate loops in the transverse or sigmoid colon and facilitate more rapid insertion.
Traversing the left colon can be challenging. The scope tip is advanced by pulling back on the endoscope, causing paradoxical insertion (Figure 5A). The scope tip is centered in the lumen, and suction is applied (Figure 5B) to further advance the scope through the colon. The appendiceal and ileocecal orifices may be recognized when the cecum is reached. The appendiceal orifice often appears on a “crow's foot,” and the three taeniae form a confluent fold leading to the orifice (Figure 5C). In many examinations, the appendiceal orifice may not be seen. Reaching the cecum can be confirmed by feeling the scope tip in the patient's right lower quadrant through the abdominal wall or seeing the light transilluminating through abdominal wall (Figure 5D).
(5) Reaching the cecum can be confirmed by feeling the scope tip in the patient's right lower quadrant through the abdominal wall or by seeing the light transilluminating through the abdominal wall.
Attempt to intubate the ileocecal orifice, which often appears as a slit on the medial wall 3 cm above the pole (i.e., most proximal portion) of the ascending colon (Figure 6A). First, aspirate the fluid from the cecal pole. The ileocecal orifice often is angled downward, and several attempts may be required for intubation. Angle the scope tip toward the orifice, and position the tip just past the orifice (Figure 6B). Gently withdraw the scope (Figure 6C) until the angled tip flattens the D-shaped mucosal fold. After the instrument visualizes the ileocecal orifice and the valve begins to open, the instrument is straightened and advanced. Paradoxical advancement by withdrawal of the scope can aid in entering the terminal ileum.
(6) Attempt to intubate the ileocecal orifice.
Visualization is performed on withdrawal of the scope. Withdrawal must be slow, with careful inspection of the entire circumferential wall before the scope is moved. Inspect behind every fold to ensure hidden lesions are not missed.
(7) Visualization is performed during slow withdrawal of the scope, inspecting behind every fold to ensure hidden lesions are not missed.
After a polyp is discovered, the scope is positioned a few centimeters away. The electrocautery snare is inserted through the biopsy channel. The snare sheath is positioned next to the polyp, the wire loop is advanced over the polyp, and the wire loop is slowly secured over the base of the polyp or pedicle. The scope tip is maneuvered so that the snare loop is not touching colon wall to reduce the risk of perforation. Apply the electrocautery current.
(8) Electrosurgical polypectomy.
PITFALL: Colonic explosion has occurred in individuals undergoing electrosurgical polypectomy. Explosion of intraluminal methane gas is unlikely if the colon has been adequately prepped.
Small polyps can be retrieved through the scope using the snare or grasping forceps. Larger polyps can be removed by suctioning the polyp against the scope and withdrawing the scope.
(9) Small polyps can be retrieved through the scope using the snare or grasping forceps, and larger polyps can be removed by suctioning the polyp against the scope and withdrawing the scope.
PITFALL: Reinsertion of the scope may be needed if the scope has to be withdrawn to remove a large polyp and the tip cannot adequately visualize the colon wall.
PITFALL: Occasionally, polyps fall away or are mishandled, or a large number must be removed. Unretrieved polyps can be recovered after the procedure. Patients may strain to move them out of the colon, or added bowel prep solution (i.e., polyethylene glycol solution or phosphate enema) can be administered through the scope to induce evacuation. The fluid is filtered so that the polyps can be recovered for histologic examination.
PITFALL: Suspected perforation after polypectomy necessitates hospital observation and evaluation.
Current Procedural Terminology (CPT®) codes listed here include the terminology “proximal to the splenic flexure” in the code descriptor. However, for reporting purposes, colonoscopy is the examination of the entire colon from the rectum to the cecum and may include examination of the terminal ileum. For an incomplete colonoscopy, with full preparation administered with the intent to perform a full colonoscopy, use the colonoscopy codes above with a -52 modifier to signify reduced services. In the office setting, a tray charge can be billed (99070 or A4550) to help cover procedure costs.
INSTRUMENT AND MATERIALS ORDERING
Information on endoscopy equipment ordering, training, and atlases can be found in Chapter 49. The information on ordering the Ives anoscope is included in Chapter 52.
Propofol (1% Diprivan) injection is available from Astra-Zeneca, Wilmington, DE (http://www.astrazeneca-us.com). Meperidine (Demerol) injection is available from Wyeth-Lederle (http://www.wyeth.com). Midazolam (Versed) injection is available from Roche, Nutley, NJ (http://www.roche.com). Recommendations for endoscopic cleaning appear in Appendix E. Guidelines for monitoring patients receiving conscious sedation appear in Appendix F
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