Definitions for the Levels of Evidence (A-C) are provided at the end of the "Major Recommendations" field.
Role of Endoscopy
Colonoscopy is indicated in selected patients to exclude obstruction from cancer, stricture, and extrinsic compression. Patients with constipation should undergo colonoscopy if they have rectal bleeding, heme-positive stool, iron deficiency anemia, weight loss, obstructive symptoms, recent onset of constipation, rectal prolapse, or change in stool caliber. Colonoscopy should also be done before surgery for constipation.
Patients over the age of 50 years who have not had prior colorectal cancer screening should undergo colonoscopy. Chronic constipation was associated with an increased risk of colon cancer in two U.S. population-based, retrospective studies (odds ratio 2.36: 95% confidence intervals [CI] [1.4, 3.93]) (relative risk 4.4 for severe constipation: 95% confidence intervals [2.1, 8.9]) but not in a prospective study of women nurses. A retrospective study from Australia also reported increased cancer risk in patients with constipation, and a retrospective study from Japan found increased risk in frequent laxative users.
In younger patients, a flexible sigmoidoscopy may be sufficient to exclude distal disease. Suspected Hirschsprung's disease requires anorectal manometry and deep biopsy to examine for the absence of myenteric neurons.
The yield of colonoscopy in isolated constipation is low and is comparable with asymptomatic patients who undergo colonoscopy for colon cancer screening. In one study of 563 sigmoidoscopies or colonoscopies done for evaluation of constipation, colorectal cancer was found in 8 (1.4%), adenomas in 82 (14.6%), and advanced lesions (cancer or adenoma with malignancy, high-grade dysplasia, villous features, or size >10 mm) in 24 (4.3%). Associated findings may include solitary rectal ulcer syndrome (indicating prolapse), anal fissure, and melanosis coli (indicating chronic laxative use).
Colonoscopy may be used to provide therapy in some patients. Fibrotic strictures from inflammatory bowel disease, surgery, or ischemia can be dilated at the time of colonoscopy. Colonoscopy has no role in stool disimpaction, although there are reports of removal of sunflower seed bezoars that were causing fecal impaction.
Chronic constipation is an independent risk factor for inadequate bowel preparation for colonoscopy. In these patients, a more aggressive regimen for colon cleansing should be considered.
Some third party payers (e.g., Medicare) may not cover colonoscopy for "constipation" or "weight loss" as the sole indication.
Summary
- Patients with constipation should undergo colonoscopy if they have rectal bleeding, heme-positive stool, iron deficiency anemia, weight loss, obstructive symptoms, recent onset of constipation, rectal prolapse, or change in stool caliber (C).
- Chronic constipation may be a risk factor for colorectal cancer (B). For this reason, patients complaining of constipation who are over the age of 50 years and who have not previously had colon cancer screening should have a colonoscopy (C).
- In younger patients flexible sigmoidoscopy may be adequate (C).
- Colonoscopy allows dilation of benign colonic strictures in some patients (B).
Definitions:
Levels of Evidence
- Prospective controlled trials
- Observational studies
- Expert opinion
