How adequate is digital rectal exam for prostate cancer screening at colonoscopy? Can adequacy be improved?

Screening by digital rectal exam (DRE) has been advocated as a means of detecting early-stage prostate cancer. We sought to determine the adequacy of prostate palpation at DRE at colonoscopy, and to devise a method of improving adequacy when the gland is incompletely felt.

Adequacy of prostate palpation in the left lateral position was prospectively assessed in 200 males 40 years or older undergoing colonoscopy, and correlated with body mass index (BMI) and National Institutes of Health (NIH) weight categories. If the prostate was incompletely felt, the patient was asked to flex his knee(s) up toward his chest, and then the exam was repeated.

The prostate was incompletely felt on initial DRE in 65 of 200 patients (32.5%). Raising the knee(s) toward the chest permitted complete palpation in 62 of those 65 cases. Incomplete palpation showed a strong correlation with BMI (P < 0.0001) and weight category: 3/36 (8.3%) for patients with normal body weight, 14/89 (15.7%) for overweight, 42/68 (61.8%) for obesity, and 6/7 (85.7%) for extreme obesity (P < 0.0001). There were 13 patients in whom no part of the prostate gland could be felt on the initial DRE, and which also correlated with NIH weight class (P < 0.0001).

The prostate gland is often incompletely palpated at DRE in the left lateral position at colonoscopy, and shows a strong correlation with obesity. Adequacy can be dramatically improved by having the patient raise his knee(s) up toward his chest, a maneuver that takes just seconds to perform.