Consider colonoscopy for young patients with hematochezia
Adenomas
Adenomas were found in 9.9% of our patients. A similar incidence was found in a series that studied the utility of anoscopy in addition to lower endoscopy.28 Only 1.8% of our patients had adenomas 8 mm, and all of these polyps were located in the distal colon. The incidence of adenomas <8 mm was 8.1%, and a third of the patients had polyps in the proximal colon. The relationship of these small adenomas to rectal bleeding is unclear as some of these patients also had hemorrhoids or diverticulosis. Polyps are common, bleed infrequently, and seem to be identified by chance during the investigation of GI bleeding.29-30
Choosing diagnostic tests for younger patients
Choosing between flexible sigmoidoscopy and colonoscopy for younger patients with rectal bleeding is a clinical dilemma. Most of the literature regarding the evaluation of rectal bleeding has either been directed towards older adults or has failed to stratify patients by age.4-8,13-22
One large study retrospectively studied the colonoscopic findings for rectal bleeding in 280 adults younger than 40 years.11 They found significant lesions, including cancers, polyps, colitis, angiodysplasia, diverticula, and rectal ulcers in 21% and concluded that full colonoscopy should be seriously considered even in this younger population. The study did not mention the location of the significant lesions within the colon, so the basis for recommending colonoscopy is unclear. Only 13.9% of patients with rectal bleeding had visited a physician for bowel problems in the past year Also, the study included a substantial number of hyperplastic polyps listed as significant pathology. To date, hyperplastic polyps do not appear to have malignant potential.
A prospective Canadian study found that, among 61 patients younger than 55 undergoing colonoscopy for rectal bleeding, most lesions, including colitis, polyps, cancers, diverticula, and hemorrhoids, were located within 60 cm of the anus.31 However, 1 cancer in a patient with massive bleeding and 1 small polyp were beyond 60 cm. A recent cost-effectiveness analysis by Lewis et al for the diagnosis of rectal bleeding in young persons demonstrated an incremental cost-effectiveness of colonoscopy as the age of the patient increased from 25 years to 45 years.32 At 35 years, the cost-effectiveness of evaluating the whole colon approximated the cost-effectiveness of repeat screening for colorectal cancer. At age 25 years, however, the cost-effectiveness of colonoscopy was more than $270,000 per year of life gained.
By comparison, several large studies have looked at colonoscopic findings in the screening population. Screening colonoscopy detected no colorectal cancers in 906 asymptomatic persons aged 40 to 49 years.33 Adenomatous polyps occurred in 8.7% of patients and advanced polyps (adenomas 10 mm, villous adenomas, adenomas with high-grade dysplasia) occurred in 3.5% patients; 55% of the lesions were located distally. In a Veterans Affairs study, advanced proximal neoplasias or invasive cancer were found in about 10% of patients older than 50 years undergoing screening colonoscopy.34 Of those with advanced proximal adenomas, only 48% had distal adenomas, supporting a role for colonoscopy over flexible sigmoidoscopy in the screening population.
Although none of the advanced adenomas or colon cancers were localized to the proximal colon, our study was not designed to determine the superiority of flexible sigmoidoscopy or colonoscopy. One important point is that flexible sigmoidoscopy at our institutions involves a full colon preparation and, in over 90% of cases, examines the distal 60 cm of colorectum (typically at or near the splenic flexure). Other studies reporting on flexible sigmoidoscopy use only enema preps and evaluate the distal colon less extensively.
The difficulty with more limited colon exams, such as anoscopy, rigid sigmoidoscopy, or flexible sigmoidoscopy, is whether or not a full colonoscopic exam should be performed when only benign anorectal pathology, namely hemorrhoids and anal fissures, are found. Hemorrhoids and anal fissures are the major cause of rectal bleeding and, because they are common, they can be coincident with more significant colon diseases, such as tumors and colitis. In our study, hemorrhoids were the only colonoscopy finding in 73% of the patients with hemorrhoids. The other 27% with hemorrhoids had coincident colorectal pathology, including adenomas and colitis, arguing that the discovery of hemorrhoids on a limited exam of the anorectum should not discourage practitioners from pursuing more detailed exams, such as colonoscopy. We can speculate that anoscopy alone would have missed a significant number of patients with cancers, adenomas, and chronic colitis.
Results and limitations of this study
The results of our study are significant in that approximately 12% of patients younger than 50 years with rectal bleeding had colon neoplasms, including 4 with colon cancers. Furthermore, an additional 13 patients had chronic colitis, another important finding with significant clinical implications for therapy and colorectal cancer surveillance.
