MR imaging of traumatic posterior urethral injury.

To assess the role of magnetic resonance (MR) imaging in defining the surgical approach and in predicting permanent erectile dysfunction in patients with traumatic posterior urethral injury, 27 patients underwent MR imaging before open urethral reconstruction. MR findings were correlated with surgical findings, surgical approach, and sexual potency at 12-month follow-up. MR imaging correctly revealed the length of the urethral injury (allowing for 0.5-cm discrepancy) in 23 of 27 (85%) patients and displacement of the prostatic apex in 19 of 21 (90%) patients. MR findings prompted a change in the clinically planned surgical approach from perineal to combined perineal and transpubic in seven (26%) cases. Significant variables affecting permanent impotence were avulsion of the corpus cavernosum, (P < .001), separation of the corporeal body (P < .05), and superior and/or lateral prostatic displacement (P < .05). When MR imaging findings of both cavernous avulsion and superior and/or lateral prostatic displacement were present, the probability of permanent impotence was 95%. In the absence of these findings, the probability of normal potency was 83%. MR imaging can be performed to help select the most effective surgical approach and to assess permanent erectile dysfunction.