Colonic polyp

In medicine, colonic polyps are "discrete tissue masses that protrude into the lumen of the colon. These polyps are connected to the wall of the colon either by a stalk, pedunculus, or by a broad base."

High risk colonic polyps are either:
 * 3 or more synchronous adenomas
 * adenomas ≥1 cm in diameter
 * villous histology or high-grade dysplasia

The risk of dysplasia depends on the size of the polyp:

Screening
A clinical practice guideline jointly written by the American Cancer Society and other groups recommends one of:
 * Flexible sigmoidoscopy every 5 years
 * Barium enema every 5 years
 * Virtual colonography (a noninvasive test based on computed tomography) every 5 years
 * Colonoscopy every 10 years

When polyps are found, a clinical practice guideline jointly written by the American Cancer Society and other groups states:
 * High risk polyps are 1) 3 or more synchronous adenomas, 2) adenomas ≥1 cm in diameter, or 3) villous histology or high-grade dysplasia.
 * High risk polyps should have follow-up colonoscopy in 3 years
 * Low risk polyps should have repeat colonoscopy in 5 to 10 years
 * If no adenomas are found, follow-up evaluation should be at 10 years

A validation of these guidelines found:
 * High risk adenomas - 9% of an advanced adenoma at 4 years of follow-up.
 * Low risk adenomas - 5% of an advanced adenoma at 4 years of follow-up.