Magnetic resonance urethrography to assess obliterative posterior urethral stricture: comparison to conventional retrograde urethrography with voiding cystourethrography.

PURPOSE: We prospectively evaluated magnetic resonance urethrography for depicting obliterative posterior urethral stricture.

MATERIALS AND METHODS: A total of 25 men with a mean age of 48.7 years (range 21 to 72) with complete posterior urethral stricture were studied preoperatively with axial and sagittal turbo spin-echo T2, sagittal T1 and contrast enhanced sagittal T1-weighted images. Of the 25 patients 22 underwent conventional retrograde urethrography with voiding cystourethrography. For magnetic resonance urethrography aseptic lubricant was infused through the external urethral meatus to dilate the distal urethra up to the stricture. Each imaging result was compared with a surgical specimen or a description of the surgical findings. Measurement errors were analyzed using the Wilcoxon signed rank test. The relationship between true and measured stricture length was evaluated by linear regression analysis.

RESULTS: Based on magnetic resonance urethrography findings 2 patients with a less than 1 cm stricture were treated with internal urethrotomy, 21 with a more than 1 cm stricture underwent open urethroplasty and 2 with prostatic displacement and a 4 cm stricture needed the combined perineal and transpubic approach. The mean +/- SD measurement error on magnetic resonance urethrography imaging was significantly lower than that on conventional retrograde urethrography combined with voiding cystourethrography (0.4 +/- 0.4 vs 1.4 +/- 1.1 cm, p <0.001). Linear regression analysis showed a stronger linear relationship between magnetic resonance urethrography and surgical measurement (r(2) = 0.62, p <0.01).

CONCLUSIONS: Magnetic resonance urethrography is more effective for evaluating obliterative posterior urethral stricture than retrograde urethrography combined with voiding cystourethrography.