Do distal adenomas mandate total colonoscopy?

Distal adenomas have been considered markers of proximal neoplasms. It also has been suggested that patients with small, distal adenomas do not require proximal examination of the colon. This study was conducted to determine the validity of the latter recommendation.

From a total of 5,132 colonoscopies performed between 1976 and 1999, all patients from whom adenomas were removed were included. Those with previous colon resections or incomplete cecal intubation were excluded. Proximal adenomas were defined as those proximal to the sigmoid colon. Adenomas were considered advanced if they were 1 cm or larger, contained any villous component, or demonstrated severe dysplasia.

The study included 226 patients. Overall, 98 patients had distal adenomas, and there was a synchronous proximal adenomas rate of 23.4%. Patients with single, small, rectosigmoid, tubular adenomas had proximal adenomas at a rate of 28.8%, and 9.6% were advanced adenomas. Patients with advanced distal adenomas had synchronous proximal adenomas at a rate of 18.9%, and 10.8% of these were advanced adenomas. According to multiple logistic regression, the strongest predictor of proximal neoplasia was the absence of distal polyps.

These data confirm the necessity for total colonoscopy in all patients with distal adenomas regardless of size. In addition, the high proportion of proximal neoplasia without distal markers suggests that full colonoscopy may be warranted as a screening tool in all patients.