In the patients with BPH the place of ultrasound estimated bladder weight in predicting infravesical obstruction

Abstract

Introduction: The differential diagnosis and treatment of infravesical obstruction is one of the most common interpretations in daily urology practice. The aim of this study was to evaluate the ultrasound estimated bladder weight as a non-invasive diagnostic tool in infravesical obstruction by comparing with other standard, parameters such as symptoms, maximum urinary flow, post-voiding residual urine, prostate volume and pressure-flow studies. Materials and Methods: Forty-nine men, aged between forty and eighty five years old (mean age 63), with lower urinary tract symptoms were investigated at Urology Department of Pamukkale University School of Medicine by International Prostate Symptom Score, physical examination, urine analysis, serum prostate specific antigen levels and renal function tests, uroflowmetry and ultrasound estimated bladder weight. Abdominal ultrasonography was done with General Electric RT-X 200. Bladder wall thickness was measured from three different places with a one centimeter distance from each other and bladder weight was calculated from bladder wall volume. Urodynantic studies were done with Life-Tech Janus IV. Cystometry and pressure-flow studies were also performed to all patients. Maximal detrusor pressure, detrusor opening pressure, maximum urinary flow at pressure-flow study (PdetQmax) and detrusor pressure at minimum flow rate were recorded. Abrams-Griffith (A-G) and lineer uretral passive resistance relationship (LUPRR) nomograms were used for determining obstruction. One-way Anova, Mann-Whitney U and Pearson correlation tests were used for statistical analysis and p<0.05 was accepted as significant. Results: 18 (%36) and 31 (%58) patients were grouped as nonobstructive and obstructive according to the urodynamic study, respectively. 49 patients' mean bladder weight was 48.7:±17.3 gr and the mean bladder weight was 38.7±3.7 and 54±2.8 gr in nonobstructed and obstructed group, respectively. While there was no significant difference for maximum urinary flow rates, post-void residual urine and prostate volumes were statistically different in two groups. A statistically significant difference was observed between urodynamically proven obstructed and unobstructed groups according to the ultrasound estimated bladder weight (p<0.05). There was a significant Pearson correlation between ultrasound estimated bladder weight and A-G number (r=0,592), Schafer grade (r=0,581), Pdet Qmax (r=0,574), detrusor contraction force and contractility (r=0,495). Twenty-nine of the thirty-seven patients with a bladder weight above 35gr and two of the twelve patients with a bladder weight below 35gr were found obstructive. When the cut-off value of bladder weight is considered as 35gr, the sensitivity, the specificity, the positive and negative predictive values were 93%, 55%, 78% and 83%, respectively. Conclusion: Ultrasound estimated bladder weight seems to be a non-invasive and reliable tool for predicting infravesical obstruction but urodynamic studies, an invasive method, is still gold standard diagnostic tool in patients with lower urinary tract symptoms. Prospective studies with larger number of patients with new cut-off values are needed to define the exact place of ultrasound estimated bladder weight in predicting infravesical obstruction.