Role Of Magnetic Resonance Imaging In Assessment Of Posterior Urethral Distraction Defects

UroToday.com- Proper assessment of post traumatic posterior urethral distraction defects is crucial for the selection of the correct surgical procedure and to aid in the ease of operative repair. Factors which affect the complexity of the procedure are length of urethral defect, degree of prostatic displacement, extent of scar tissue, and the presence of paraurethral bladder base fistula or false passage. Currently, the cornerstone of pre-operative management is the combined retrograde and antegrade urethrography. The filling of this proximal segment is sometimes difficult and may require a cystoscopy via the suprapubic tract to opacify the proximal segment with contrast to allow for the image to be obtained.MRI has been recently introduced as a potentially valuable imaging tool by Dr. McAninch's group in San Francisco. The usefulness of this study was recently evaluated by M. Koraitim and I. Reda from Alexandria Egypt. The manuscript is published in the September 2007 issue of Urology.A total of 21 patients with posterior urethral distraction defects underwent MRI of the pelvis an addition to combined antegrade and retrograde urethrography as part of their pre-operative assessment. Repair was then performed with a bulboprostatic urethral anastomosis in the standard fashion. Twelve patients were performed via a perineal approach while 8 patients required transpubic repairs.MRI was able to accurately measure the distraction defect in 18 patients (86%) and underestimated the defect by 0.5 to 1.0 cm in 3 patients (14%). In contrast, the length of the defect could not be measured by standard urethrography in 6 patients (30%) due to incomplete or absent proximal urethral segment filling. Prostatic displacement either laterally or posteriorly was also able to be correctly discerned. Avulsions of the corpus cavernosum were diagnosed in 6 patients- all of which had potency issues pre-operatively.The MRI findings altered surgical technique in many cases and was reliable in imaging the distraction defects even in cases when standard studies failed. I would add editorially that special interest must be present by the radiologist interpreting the study to assure that the pre-operative questions are answered. The study should also be reviewed simultaneously by the urologist and radiologist while protocols are being established.Koraitim MM, Reda ISUrology. 70(3):403-6, September 2007doi:10.1016/j.urology.2007.04.039Reported by UroToday.com Contributing Editor Michael J. Metro, M.D