Why do digital rectal exams?
In an audio CME program on preventive care, the lecturer on prostate cancer stated that “prostate-specific antigen (PSA) is recommended for screening; digital rectal examination (DRE) has no real value.” The lecturer on colon cancer stated that “DRE with guaiac test in the office is proven ineffective and not an approved option.” So if the DRE is not recommended to screen for prostate or colon cancer, why do we do it?
—Daniel E. Konold, DO, Canal Winchester, Ohio
The importance of DRE as part of a screening program for prostate cancer cannot be emphasized enough. It is categorically wrong to assume that a normal PSA rules out prostate cancer and therefore negates the need for a DRE. As many as 25% of patients with prostate cancer have a PSA <4.0 ng/mL (Walsh P, Wein AJ, Retik AB, Vaughan ED, eds. Campbell's Urology. 8th ed. Philadelphia, Pa.: Elsevier; 2002:3063).
—David T. Noyes, MD
I agree with Dr. Noyes about the importance of DRE. It is crucial in detection of anal and low-lying rectal masses. Experts do not suggest guaiac testing on stool obtained at DRE because of false positives. However, this is common practice, and any positive test should lead to colonoscopy. If guaiac testing is the only screening test the patient accepts, then stool specimens should be taken from samples collected on three consecutive days. Even this will have significant false-positive and false-negative results, but any screening test for colorectal cancer is better than none at all.
—Christina M. Surawicz, MD (125-3)