Background: Proximal colonic adenomas were found in 13% to 37% of patients without distal adenomas who underwent colonoscopy. Fiberoptic flexible sigmoidoscopy (FFS) was not performed prior to colonoscopy in all studies except one. The proximal colon at colonoscopy was defined as that portion of the colon proximal to either the descending-sigmoid junction or 60 cm from the anus while withdrawing the colonoscope. These estimates may not reflect exact colonic location when a 60 cm length sigmoidoscope is fully inserted. Therefore, the aim of our study was to determine the prevalence of proximal colonic neoplasms in asymptomatic patients with average risk for colon cancer, aged 50 years and over, with negative fecal occult blood tests and without adenomas at FFS.
Methods: Colonoscopy was performed in 80 patients without and 95 patients with adenomas at FFS. Polypectomy was done using hot biopsy forceps or snare cautery.
Results: Twenty-four proximal colonic adenomas (19 < 1 cm and 5 > or = 1 cm) were found in 18 of 80 patients (23%) with normal FFS compared with 39 proximal colonic adenomas (32 < 1 cm and 7 > or = 1 cm), in 28 of 95 patients (29%) with adenomas at FFS (p = 0.31). In patients with normal FFS, there were 20 tubular, 2 tubulovillous, and 2 villous (1 with severe dysplasia) adenomas. In patients with adenomas at FFS, there were 31 tubular, 5 tubulovillous, and 3 villous (1 with severe dysplasia) adenomas.
Conclusions: Proximal colonic adenomas are found in up to one fourth of asymptomatic average-risk patients with negative fecal occult blood test and both with and without adenomas at FFS. The adenomas in both groups have similar size, histology, and location. Severe dysplasia is rarely present.