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Jeffrey A. German, MD and Clint N. Wilson, MD



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Subject: Colonoscopy

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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 clean equipment to ensure patient safety. Video colonoscopes enable complete examinations of the entire colon in more than 90% 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 years and 55% at age 80 years. 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 <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 a cost-effective strategy. 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 >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 >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 hyperplastic 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 that 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 shown 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. Procedural (Conscious) Sedation contains guidelines for monitoring the patient receiving conscious sedation at endoscopy. 
Polypectomy is the most commonly performed therapeutic procedure during colonoscopy. With regard to polyps found at the time of endoscopy, 85% to 90% can be removed with the endoscope, but patients can experience considerable morbidity from bleeding or colon perforation due to 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. 
Colonoscopy can be safely learned only with direct, one-on-one supervision by an experienced proctor or preceptor. Debate exists about the number of procedures that trainees need to perform to become competent in colonoscopy, and no scientific data currently exists correlating the volume of colonoscopies performed with acquisition of competence. Individual practitioners have varying levels of manual dexterity and experience with flexible sigmoidoscopy and can acquire skills at differing rates. Studies show that when observable factors are used to determine technical competency in colonoscopy (reach-the-cecum rate, time to complete procedure, and rate of complications), family physicians, gastroenterologists, and general surgeons are all comparable. 


  • Conscious sedation drugs and equipment

  • Colonoscope and video monitoring equipment

  • Biopsy forceps, snare, electrosurgical generator


  • Evaluation of a radiographic abnormality

  • Screening of asymptomatic individuals for colon neoplasia or cancer

  • Evaluation of unexplained gastrointestinal bleeding

  • Positive FOBT

  • Unexplained iron-deficiency anemia

  • Examination for a synchronous colon neoplastic lesion when a lesion is found in the rectosigmoid

  • Surveillance or follow-up study after removal of a prior neoplastic lesion

  • Suspected inflammatory bowel disease or surveillance for previously diagnosed inflammatory bowel disease

  • Evaluation of symptoms suggestive of significant colon disease (e.g., chronic diarrhea, weight loss, abdominal or pelvic pain)

  • Therapeutic procedures (e.g., polyp removal, foreign body removal)

Contraindications (Relative)

  • Fulminant colitis

  • Acute diverticulitis

  • Hemodynamically unstable patient

  • Recent (<3 months) myocardial infarction

  • Recent (<1 week) bowel surgery

  • Uncooperative patient

  • Coagulopathy or bleeding diathesis

  • Known or suspected perforation

  • When the procedure results will not produce a change in management

The Procedure

Step 1

The patient is placed on the examination table in the left lateral position. Intravenous access is obtained, and sedation is administered. Appropriate patient monitoring includes frequent vital signs, oximetry, and heart rhythm (electrocardiographic) evaluation throughout the procedure. Flexible Sigmoidoscopy provides instruction for scope insertion and examination techniques in the rectosigmoid during colonoscopy. 

Step 2

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 Flexible Sigmoidoscopy for techniques to pass through this area). Insert the scope only through visible lumen. The wall of the descending (left) colon has a characteristic circular appearance with encircling folds. 
  • PITFALL: Sliding the scope along the colon wall (i.e., slide-by technique) is not advocated, as this technique may result in perforation at the rectosigmoid junction.

Step 3

A sharp turn appears at the splenic flexure. A bluish color of the vascular spleen may be visible through the colon wall. 

Step 4

A sharp turn of the scope tip (with torquing) often is required to pass through the splenic flexure. 
The lumen of the transverse colon has a characteristic triangular appearance. 

Step 5

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. 

Step 6

The examiner 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. 

Step 7

Avoid the 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. 

Step 8

Traversing the left colon can be challenging. The scope tip is advanced by pulling back on the endoscope, causing paradoxical insertion. The scope tip is centered in the lumen, and suction is applied to further advance the scope through the colon. The ileocecal and appendiceal orifices may be recognized when the cecum is reached. The appendiceal orifice (shown) often appears on a “crow’s foot,” and the three taeniae form a confluent fold leading to the orifice. In many examinations, the appendiceal orifice may not be seen. Feeling the scope tip in the patient’s right lower quadrant through the abdominal wall or seeing the light transilluminating through abdominal wall can help to assure the endoscopist that the cecum has been reached, but seeing landmarks such as the appendiceal orifice, “crow’s foot,” and ileocecal valve are necessary to confirm the scope’s location within the colon. 

Step 9

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. 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. Gently withdraw the scope until the angled tip flattens the D-shaped mucosal fold. 

Step 10

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. The terminal ileal mucosa has a characteristic “cobblestone” appearance. 
Step 10
Step 10

Step 11

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 that 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. In order to reduce the risk of performation, the scope tip is maneuvered so that the snare loop is not touching the colon wall. Apply the electrocautery current. 
  • PITFALL: Colonic explosion has occurred in individuals undergoing electrosurgical polypectomy. Explosion of intraluminal methane gas is unlikely if the colon has been adequately prepped.

Step 11
Step 11

Step 12

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. 
  • PITFALL: Reinsertion of the scope may be needed if the scope has to be withdrawn to remove a large polyp. The polyp may obscure the scope tip, making adequate visualization of the colon wall during withdrawal difficult.

  • 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.

Step 12
Step 12


  • Perforation: 1 to 2 per 1,000 procedures (studies from diagnostic colonoscopies only, however)

  • Bleeding following polypectomy

  • Adverse reaction from sedatives such as respiratory depression, allergic reaction, or cardiac dysrhythmia

Pediatric Considerations

Pediatric endoscopes are available, which have a narrower diameter than adult endoscopes. 

Postprocedure Instructions

Patients are usually monitored for 30 minutes after the procedure to make sure that they have recovered completely from sedation. Someone must drive them home, but they can resume a regular diet right away. They should be warned to contact their provider immediately if they experience severe abdominal pain (not just gas cramps); a firm, distended abdomen; vomiting; fever; or bleeding greater than a few tablespoons. 

Coding Information and Supply Sources

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. 

Common ICD-9 Codes

Instrument and Materials Ordering

  • Recommendations for endoscope cleaning appear in Appendix K: Recommendations for Endoscope Disinfection

  • Complete endoscopy equipment such as endoscopes, light sources, video endoscopy monitors, cleaning and disinfection aids, and mouthpieces are available from the following manufacturers:

    Olympus Corporation, Center Valley, PA (

    Pentax Precision Instrument Corporation, Montvale, NJ (

  • Intravenous materials (e.g., intracaths, normal saline solution, intravenous tubing) can be obtained from local hospitals or surgical supply houses.

  • Propofol (1% Diprivan) injection is available from AstraZeneca, Wilmington, DE ( Meperidine (Demerol) injection is available from Wyeth-Lederle ( Midazolam (Versed) injection is available from Roche, Nutley, NJ (

  • Guidelines for monitoring patients receiving conscious sedation appear in Procedural (Conscious) Sedation.


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