Role of magnetic resonance imaging in assessment of posterior urethral distraction defects.

OBJECTIVES: To determine the clinical usefulness of magnetic resonance imaging (MRI) in the assessment of posterior urethral distraction defects.

METHODS: A total of 21 male patients, 6 to 35 years old, with posterior urethral distraction defects underwent MRI of the pelvis and combined antegrade retrograde urethrography before surgical repair. Repair was performed with a bulboprostatic urethral anastomosis through the perineum in 13 patients and transpubically in 8. The MRI and urethrographic findings were compared and correlated with the operative findings. The MRI findings were also correlated with the incidence of posttraumatic impotence.

RESULTS: On MRI, the length of urethral defect and type of prostatic displacement could be correctly determined in 86% and 89% of the patients, respectively. Also, MRI precisely delineated the extent of scar tissue, which varied according to the type and magnitude of the original trauma. Furthermore, MRI revealed the presence of paraurethral false tracks in 3 patients. In addition, MRI demonstrated avulsion of the corpus cavernosum, as well as lateral prostatic displacement in all 6 patients with posttraumatic impotence.

CONCLUSIONS: Preoperative MRI can provide useful information that might help determine the appropriate surgical repair. It correctly estimates the length of the urethral defect, clearly demonstrates the type and degree of prostatic displacement, precisely delineates the site and density of scar tissue, and reveals the presence of paraurethral false tracks. Also, MRI can identify the cause of posttraumatic impotence such as avulsion of the corpus cavernosum and thus might predict the potency outcome in these cases.