A second look at colonoscopy: indications, failures, and costs.

Results of colonoscopy and colonoscopic polypectomy in 599 patients have been reviewed. Added experience has not decreased the number of failures--failure to examine the entire colon, polyps not retrieved for histological examination ("lost polyps"), undetected ("missed") lesions, and false-negative biopsy specimens. The incidence of invasive carcinoma in polyps measuring under 1 cm is less than 1%; polypectomy should be reserved for larger lesions or demonstrated growth of small polyps. Diagnostic colonoscopy in selected patients (those with persistent gross or occult rectal bleeding but normal results from sigmoidoscopic and barium enema studies) demonstrates a causative lesion in greater than 25% and detects a cancer in 5% to 10% of patients.