Role Of Sonourethrography In The Evaluation Of Anterior Urethral Stricture-A One Year Hospital Based Observational Study

Abstract

Background & objectives Urethral stricture is a pathology involving the anterior urethra or fibrosis involving the urethral epithelium or corpus spongiosum (spongiofibrosis). The post-operative result of a urethral stricture depends on appropriate pre-operative evaluation, thus accurate preoperative examination and investigations are essential for better post-operative results. The determining points or parameters to the surgical approach are precise measurement of extent of anterior urethral narrowing along with spongiofibrosis. Radiographic retrograde urethrography or ascending urethrography is considered as the gold standard investigation for identification of urethral stricture affecting anterior urethra. Retrograde urethrography is 91% sensitive and 72% specific in the diagnosis of anterior urethral stricture. Limitations of retrograde urethrography or ascending urethrography are poor definition of stricture length involving proximal portion of bulbar urethra and periurethral spongiofibrosis. Retrograde urethrogram requires multiple image acquisition like right and left oblique views. The radiation exposure is approximately 1-2 mSv which equals approximately 20 thorax x-rays and half year of environmental radiation. Sonourethrogram is a 3-dimentional technique with advantages of being radiation free and easy repeatability. Sonourethrogram detects stricture and determines its parameters like length and spongiofibrosis. It can also identify complications like fistula formation, diverticulum etc. The objectives of this study are to establish the sensitivity of sonourethrography in the identification of the anterior urethral stricture and to determine the accuracy of sonourethrography in measuring the span of anterior urethral stricture as well as to detect spongiofibrosis. Materials and methods One year prospective observational study was done in Department of Radio-diagnosis at the KLE’S Dr. Prabhakar Kore hospital & MRC, Belagavi. 30 patents were included in the study. These patients are subjected to retrograde urethrography and sonourethrography to detect, measure the length and degree of spongiofibrosis in anterior urethral stricture disease. Sensitivity, specificity, positive and negative predictive values of sonourethrography were calculated. Unpaired t-test was used to determine its ability to measure the length of the anterior urethral stricture. The values were then compared with retrograde urethrgraphy and intra-operative results. The percentage of patients detected to have spongiofibrosis on sonourethrography was also computed. Results The sensitivity and specificity of sonourethrogram as compared to ascending urethrogram was found to be 92% and 100% respectively with positive and negative predictive values of 100% and 71.43% respectively. In this study sensitivity and specificity of sonourethrogram as compared to intra-operative results were 92% and 100% respectively with positive and negative predictive values of 100% and 71.43% respectively. In the current study ascending urethrogram and intra-operative findings correlated well with 100% sensitivity, specificity, positive and negative predictive values. Interpretation and conclusion Urethral obstructive pathologies are one of the common problems presenting to the urosurgeon. Urethral obstructive conditions are divided into those involving anterior and/or posterior urethra. Radiographic imaging is the gold standard imaging investigation. Other investigations which can be used are sonography, cystoscopy, computed tomography and magnetic resonance imaging. Ascending urethrography has high sensitivity and specificity in identification of anterior urethral strictures. Sonourethrography has extra advantage of identifying the degree of spongiofibrosis and precisely measuring the length of stricture. Thus the study concluded that though radiographic imaging is the best imaging modality available, sonourethrography can also provide similar results with additional benefits like precise measurement of length of narrowing in the anterior urethra (especially the bulbar urethra) and severity of scarring of corpus spongiosum. The disadvantage of sonourethrography is that it is a poor imaging modality for identification of strictures involving the posterior urethra.