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 underwe
nt MR imaging before open urethral reconstruction. MR findings were co
rrelated with surgical findings, surgical approach, and sexual potency
at 12,month follow-up. MR imaging correctly reveal ed the length of t
he 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%) pat
ients. MR findings prompted a change in the clinically planned surgica
l 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 corpore
al body (P < .05), and superior and/or lateral prostatic displacement
(P <.05). When MR imaging findings of both cavernous avolsion and supe
rior and/or lateral prostatic displacement were present, the probabili
ty of permanent impotence was 95%. In the absence of these findings, t
he probability of normal potency was 83%. MR imaging can be performed
to help select the most effective surgical approach and to assess perm
anent erectile dysfunction.