Rectal bleeding is a common patient complaint, usually presenting as blood on the toilet paper or in the toilet bowl. The differential diagnosis for this problem includes hemorrhoids, solitary rectal ulcer, diverticular bleeding, angiodysplasia, and proctitis. Because the most serious cause is malignancy, colonoscopy often is recommended, although the usefulness of the study in this situation is unclear. Lieberman reviewed the potential management strategies for patients with minor rectal bleeding.
Careful history alone can be useful if the pre-test likelihood of malignancy is extremely low. The latter may be true in persons younger than 40 years with no family history of colorectal cancer. Colonoscopy may reveal some other important pathology such as colitis or solitary ulcer, but these patients often have additional symptoms. Patients with significant bleeding or a family history of colorectal cancer should have colonoscopy. Anoscopy can identify hemorrhoids and anal fissures, but the common nature of these problems does not eliminate the possibility of an additional pathology that might actually be responsible for the rectal bleeding. Flexible sigmoidoscopy may be useful in patients younger than 40 years, because most lesions in this age group are located in the distal colon, but efficacy is lower in older patients. In persons 40 to 59 years of age, the prevalence rate of colorectal cancer increases, and colon evaluation should be performed in patients with rectal bleeding. Colonoscopy is the best test because barium or computed tomography imaging can miss significant colon pathology and subtle mucosal lesions.
Small colonic polyps under 10 mm in diameter are commonly found. Most are adenomas, with lesions in the right colon more likely to be neoplastic than those in the left colon. Small polyps in the distal colon are equally likely to be adenomatous or hyperplastic polyps. The presence of distal adenomas increases the risk of proximal advanced neoplasias. Although small-polyp risk for high-grade dysplasia or cancer is less than 0.5 percent, biopsy is useful to determine future surveillance and management.
Care of patients with small distal polyps may include no further evaluation if the polyp is hyperplastic. If the polyp is an adenoma, colonoscopy may be appropriate, especially if risk factors for colorectal cancer are present, although advanced proximal neoplasia risk in patients younger than 59 years is low. Colonoscopy is appropriate if the distal polyp is an adenoma, if histology is unknown, or if the patient is 60 years or older. Surveillance colonoscopy is indicated at least every five years in low-risk patients who had one to two small adenomas removed. Patients discovered to have three or more small tubular adenomas and those who have a more advanced adenoma that was completely removed should have surveillance colonoscopy every three years. These recommendations all assume that bowel preparation was adequate and that the examination was complete to the cecum. High-risk patients should be re-evaluated one year after the initial colonoscopy and then, if the examination is negative, every three to five years.
The author concludes that minimal rectal bleeding and small distal colon polyps are common. Malignancy risk is low in young patients who do not have a family history of colorectal cancer. Recurrence of rectal bleeding should be managed with examination of at least the distal colon. If a small polyp is found and noted to be adenomatous on biopsy histology, colonoscopy is recommended. Colonoscopy is not recommended if the small distal polyp is noted to be hyperplastic.