The value of digital rectal examination in assessing for pelvic fracture-associated urethral injury: what defines a high-riding or nonpalpable prostate?

BACKGROUND: The Advanced Trauma Life Support Manual (8th ed.) recommend a digital rectal examination (DRE) as part of the initial evaluation of all trauma patients. A "high-riding" or "nonpalpable" prostate is a contraindication to urethral catheterization and an indication for urethrography. However, there are no published guidelines on, definitions of, or predictive values for high riding. Moreover, prostate evaluation can be difficult in the supine/trauma position.

METHODS: A total of 100 patients underwent DRE in lateral decubitus position. Prostate size and distance from anal verge to the prostate apex were recorded. DRE in the supine position was then performed, noting the most proximal part of the prostate that was palpable. High-riding prostate was defined as the apex being one or more SDs farther from the anal verge than the mean. Fifty index finger lengths were measured to ensure that DRE findings were applicable to the average examiner.

RESULTS: A total of 100 prostates were evaluated. Mean (SD) distance from the anal verge to the prostate apex in patients with palpable prostates was 4.86 (1.38) cm (range, 2.5-8 cm). The prostate was nonpalpable in the decubitus position in 8 of the 100 patients and in the supine position in 42 of the 100 patients. Mean (SD) body mass index in the nonpalpable group was 32.6 (5.8) kg/m versus palpable group with 28.1 (5.7) kg/m (p < 0.01). Of the 100 patients, 26 had prostates that were "high riding" (defined as >6.2 cm from the anal verge), 2 of which were palpable in the supine position. Palpable prostates were closer to the anal verge at 4.13 cm compared with nonpalpable at 6.15 cm (p < 0.01). Mean (SD) index finger length is 7.3 (0.60) cm.

CONCLUSION: DRE in the pelvic fracture trauma setting to evaluate for urethral disruption is unreliable. Patients with a larger body mass index were less likely to have a palpable prostate. The use of the criteria of "nonpalpable" prostate has a high false-positive rate. Our objective definition of high-riding prostate should be incorporated into all trauma protocols.

LEVEL OF EVIDENCE: Epidemiologic study, level V.