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January 1991

nal radiation, colonoscopy or barium enema within 3 years performed for any indication, prosthetic heart valve, and use of anticoagulants. Volunteers who had recently undergone screening sigmoidoscopy were not excluded, provided they had not undergone colonoscopy or barium enema within 3 years. Most patients with previous colonoscopy and barium enema or flexible sigmoidoscopy had the procedures as screening exams. If previous exams had been performed for symptoms, the symptoms must have been resolved for a minimum of 2 years. All subjects underwent home fecal occult blood testing [Hemoccult II slides; Smith Kline Diagnostic, Inc., San Jose, CA) on each of 3 consecutive days] during the week before starting the colonoscopy preparation. All subjects answered a questionnaire designed to confirm their asymptomatic status. Subjects were asked whether in the previous 3 months they had noticed diarrhea, constipation, pencil-thin bowel movements, lower abdominal pain, rectal pain, pruritus ani, or hematochezia. Any subject who reported hematochezia, a change in bowel habit, development of abdominal or rectal pain, unless it was occasional and fleeting and similar fleeting pains had occurred previously, or a change in the frequency or severity of pruritus ani, was excluded. Any subject who had seen a physician for gastrointestinal symptoms in the previous 2 years was excluded. The colon was prepared with standard commercially available lavage solutions in all cases. Colonoscopy was performed using the Olympus V-1OL video colonoscope or CF-1OL fiberoptic colonoscope (Olympus Corp., Lake Success, NY). All examinations were performed by experienced staff gastroenterologists. Meperidine (Demerol; Winthrop Pharmaceuticals, NY) and midazolam (Versed; Roche Laboratories, Nutley, NJ) were used as needed for sedation, and the pulse and oxygen saturation were monitored with a pulse oximeter. Polyps were removed using either snares or hot biopsy forceps. Polyps < 4 mm were often cold-biopsied before removal to ensure recovery of a pathological specimen. Polyps were located within the colon using intraluminal landmarks, light transmission, and distance markers. Patients whose preparation demonstrated pools of debris were rotated between multiple positions to expose all of the colonic mucosa. After routine interpretation of the pathological slides, all slides were reviewed again blindly by one pathologist (T.U.) with a special interest in gastrointestinal pathology. Polyps were classified into categories of hyperplastic or adenoma using widely accepted criteria (14).

Results Three hundred five persons responded to the invitation, of whom 89 were excluded [first degree relative with colon cancer or polyps (45), colonoscopy or barium enema within 3 years (14), positive symptom questionnaire (11), prior polyp (ll), age (4), breast cancer (3), anemia (l)]. Six more were excluded after they tested positive for fecal occult blood. The remaining 210 subjects formed the basis of the study. Of the 210 subjects, 150 were male and 198 were

SCREENING COLONOSCOPY 65

white; the mean age was 60.1 years (range, 50-75 years). The preparation quality was judged as excellent or good in 154 subjects (i’s%), scattered solid stool in 29 (14%), and scattered pools of semi-solid debris in 27 (13%). Insertion of the colonoscope to the cecum was successful in 209 of the 210 study subjects. The average total dose of meperidine given was 58 mg and of midazolam 1.8 mg. Eleven subjects asked that the exam be attempted without sedation; in each case this was accomplished. The blinded pathological review resulted in four subjects originally interpreted to have diminutive adenomas being changed to the group with hyperplastic polyps only. No other changes in histological diagnosis resulted from the review. After pathological review, 53 subjects (25%) had adenomatous polyps, 18 had hyperplastic polyps only, and 2 had cancer. One of these was a Dukes A cancer in a 12-mm sessile polyp opposite the ileocecal valve. This subject underwent a right hemicolectomy because of cancer near the polypectomy resection line; no cancer was found in the bowel wall or adjacent lymph nodes. The second patient had a well-differentiated Dukes’ A carcinoma in a 5-cm pedunculated sigmoid polyp. There was no cancer near the polypectomy resection line, and surgery was not performed. The 53 subjects with adenomas had a total of 104 adenomas with the following size distribution: 2-4 mm (n = 63), 5-9 mm (n = 28), and 21 cm (n = 13). The largest adenoma was 2-4 mm in 28 subjects, 5-9 mm in 14 subjects and 2 1 cm in 11 subjects. Of 45 subjects aged 50-54 years, 5 (11%) had an adenoma. Of 43 subjects aged 55-59 years, 10 (22%) had an adenoma. Of 57 subjects aged 60-64 years, 17 (30%) had an adenoma. Of 65 subjects aged 65-75 years, 21 (33%) had an adenoma. Pairwise comparison of the age groups by x2 analysis showed that the 50-54-year age group had significantly fewer polyps than the 60-64-year age group (P= 0.02) and the 65-75-year age group (P= 0.01). All 11 subjects with adenomas 2 1 cm in size and both subjects with cancer were 260 years old. One hundred twenty-three subjects had undergone one or more previous colon examinations, including 74 with previous rigid and/or flexible sigmoidoscopy, 74 with previous barium enema, and 6 with previous colonoscopy. Of the 123 subjects with some previous examination, 30 (24%) had one or more adenomas including 18 (24%) of those with previous sigmoidoscopy, 17 (23%) of those with previous barium enema, and 2 of those with prior colonoscopy (33%). Of the 87 subjects with no previous examination, 23 (26%) had one or more adenomas. Nineteen of the subjects with previous sigmoidoscopy had undergone the ex-

66

GASTROENTEROLOGY

REX ET AL.

amination within 2 years (all flexible sigmoidoscopy). Three of these 19 subjects (16%) had adenomas. This was not significantly different from the rest of the 191 study subjects (P = 0.32, x2 test). Fifty-seven subjects had diverticulosis, and 119 had internal or external hemorrhoids. Table 1 lists the findings in the proximal colon (proximal to the sigmoid-descending junction) according to the findings distal to the sigmoid-descending colon junction. We also examined the findings proximal and distal to the splenic flexure and found that 19 (36%) of subjects with adenomas and 1 with cancer had no neoplasms distal to the splenic flexure. In one subject, a self-limited but major hemorrhage developed: it began 11 days after four diminutive adenomas were removed from the hepatic flexure and proximal transverse colon using hot biopsy forceps. He required hospitalization for 4 days and transfusion but no surgical, endoscopic, or angiographic therapy was needed. He was discharged in good condition. No other complications occurred in the study. Discussion We performed screening colonoscopy on 210 asymptomatic average-risk persons aged 50-75 years with negative fecal occult blood test results. The study sample was biased toward persons of relatively high socioeconomic status (physicians, dentists, and their spouses) and persons interested in cancer screening. However, neither of these factors is known to influence the incidence of colorectal neoplasms. We carefully screened the study subjects to ensure their average-risk asymptomatic status. We found a high prevalence of neoplasms (26%) in the study sample. However, this prevalence is somewhat lower than the 36%-53% detected in autopsy studies (4,5) or the 38% found in evaluation of patients with positive fecal occult blood test results (6). Table I. Proximal Colon Findings in the 210 Study Subjects According to the Findings in the Distal Colon Proximal

colon findings”

Distal colon findings

No polyp

Adenoma

n (%)

n 1%)

HP only

n (%I

Cancer

n (%)

No polyp Adenoma HP only Cancer

137(65) 14 (6) 11(51 1 (