Colonoscopy Screening Test

Colonoscopy is the most widely used diagnostic method to study the colon and has the highest diagnostic sensitivity and specificity of all available tests. In most studies, 90% to 95% of the colon can be examined. The examination has an extremely small risk of complications (0.1% to 0.2% risk of bleeding or perforation).

This single test, which usually takes an hour or less to complete, may be both diagnostic and therapeutic. The sensitivity level of colonoscopy is such that it can detect polyps greater than or equal to one centimeter in size. More than 95% of tumors are detected during a colonoscopyColonoscopy is the preferred procedure for the diagnosis of symptomatic patients. At the present time, it is the best diagnostic tool for the diagnosis of colorectal neoplasia.

A: position of the colonoscope in the colon; B: endoscopic view; C: detail of the colonoscope tip.

The patient is prepared for the procedure by the administration of a nonabsorbable gastrointestinal lavage solution, and/or laxatives. Intravenous analgesia and sedation are administered during the examination.

Colonoscopy offers the flexibility of performing a mucosal biopsy of suspicious regions and the ability to perform endoscopic polypectomy.

A: sessile polyp; B: pedunculated polyp; C: adenocarcinoma; and corresponding endoscopic views.

Most adenomatous polyps can be completely and safely removed during colonoscopy. Small polyps (<5mm) should be biopsied to determine whether they are hyperplastic polyps or adenomas. Polyps are removed with biopsy forceps, or snare resection with or without cautery.

A,B, Endoscopic colonic mucosal biopsy technique; A',B' corresponding endoscopic views

Pedunculated (with stalk) polyps can be resected with application of cautery through a snare localized around the polyp stalk.

A,B,C, Endoscopic technique for snare resection of a pedunculated polpy; B', corresponding endoscopic view.

Some sessile polyps require special techniques. Saline is injected into the submucosa area in order to elevate the polyp and facilitate removal by snare.

A,B,C, Endoscopic technique for saline assisted polypectomy; B', corresponding endoscopic view.

Large sessile polyps may be resected piecemeal with snare and cautery current. In cases of unsuccessful resection of the polyp, the patient is referred for surgery.

When large polyps are involved, it may be useful to mark the polypectomy site with India ink. Site tattooing may help localize the area during subsequent surveillance colonoscopies and may assist the surgeon in locating the area to be resected.

A,B, Endoscopic technique for marking a polypectomy site for subsequent surveillance.

The most common complications of colonoscopy and polypectomy are bleeding or bowel perforation, which occurs in 0.1%–0.2% of procedures. When performing polypectomies of large polyps, use of excessive cautery may cause perforation or full wall thickness burn (postpolypectomy coagulation syndrome). These complications tend to occur more frequently in the right colon.

A, B, C, Endoscopic technique for piecemeal removal of large polyp with a corresponding endoscopic view.

Post-polypectomy Management

Patients with only a small (<1cm) tubular adenoma do not have an appreciable increased risk of colorectal cancer and the general screening guidelines should be followed. For polyps larger than 1 cm or for multiple polyps, follow-up colonoscopies should be performed every year. In patients who have a suboptimal initial examination, colonoscopy should be repeated at 3 months. After one negative 1-year follow up, subsequent surveillance intervals may be increased to 3 years. If subsequent colonoscopy is not possible, a flexible sigmoidoscopy and an air contrast barium enema should be performed. However, it is important to individualize surveillance according to age and comorbidity of the patient.

If you are scheduled for a colonoscopy at Johns Hopkins, click here to view the Patient Preparation Instructions >>


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