Ultrasonic measurement of bladder weight as a possible predictor of acute urinary retention in men with lower urinary tract symptoms suggestive of benign prostatic hyperplasia

Acute urinary retention (AUR) is one of the most undesirable events for elderly men with benign prostatic hyperplasia (BPH). This study was designed to test the clinical utility of ultrasonic measurement of bladder weight as a predictor of AUR. A total number of 160 men visited our clinic with lower urinary tract symptoms (LUTS) suggestive of BPH and underwent urodynamic studies, including transrectal ultrasonography of the prostate and the measurement of ultrasound (US) estimated bladder weight (UEBW). Among them, 31 (19.4%) presented to our clinic with AUR. From the thickness of the anterior bladder wall measured by transabdominal ultrasonography and the intravesical volume, UEBW was calculated, supposing the bladder to be a sphere. Between patients with and without AUR, there were significant differences for age (75.4 vs. 71.1 years, p < 0.005), prostatic volume (45.5 vs. 35.8 g, p < 0.05), transition zone (TZ) volume (29.4 vs. 20.2 g, p < 0.05), TZ index (0.606 vs. 0.493, p < 0.005) and UEBW (50.3 vs. 34.7 g, p < 0.0001). A receiver-operating characteristic curve analysis demonstrated UEBW to be superior to the other prostatic ultrasonic measures in identifying AUR. Patients with LUTS suggestive of BPH having UEBW greater than 35.0 g were 13.4 times as likely to suffer from AUR. The significant association of UEBW with an increased risk of AUR suggests that it would be promising as a noninvasive urodynamic parameter capable of identifying patients at increased risk of AUR.