Role of Magnetic Resonance Urethrography in Evaluation of Male Urethral Stricture Against Conventional Retrograde Urethrography

摘要

Magnetic Resonance Urethrography (MRU) is a new and less widely used technique in the evaluation of male urethral strictures.Aim: This study intends to establish the role of MRU in the evaluation of male urethral strictures and to compare the efficacy with that of conventional Retrograde Urethrography (RUG).Materials and Methods: A total of 32 patients with symptoms of poor urinary stream and straining during micturition underwent conventional RUG followed by MRU. The parameters studied by RUG and MRU such as stricture site, number, length, diameter and associated false tracts or diverticulum were compared with intraoperative findings, which is taken as gold standard. The sensitivity, specificity, positive and negative predictive values of all the parameters was calculated. Karl pearson correlation coefficient and Wilcoxon?s signed rank test were used where appropriate. A p-value of <0.05 was considered statistically significant.Results: Both modalities had 100% sensitivity and specificity in the detection of stricture site. MRU showed better correlation with surgical findings than RUG in strictures less than 3 cm and the RUG showed better correlation with surgical findings than MRU in strictures longer than 3 cm, even though there was no significant statistical difference between the two. Stricture lengths in four cases of long penile urethral strictures with submeatal extension were underestimated by MRU. RUG overestimated the length of four cases of penile urethral stricture. Both RUG and MRU slightly overestimated the severity of strictures in the 2 to 4 mm diameter range. RUG detected all the false tracts, whereas MRU failed to detect one of the false tracts. Accuracy in the detection of spongiofibrosis in MRU was directly proportional to the severity, with no false negatives in moderate to severe degrees of spongiofibrosis.Conclusion: RUG and MRU are equally efficacious in detecting urethral strictures. MRU showed better stricture length assessment in bulbar urethra and accurately delineated posterior urethral distraction defect. MRU effectively detects and characterises spongiofibrosis, which is not possible in RUG.