Is the ultrasound-estimated bladder weight a reliable method for evaluating bladder outlet obstruction?

• To evaluate the correlation between ultrasound-estimated bladder weight (UEBW) in patients with different degrees of bladder outlet obstruction (BOO).

• We evaluated 50 consecutive non-neurogenic male patients with lower urinary tract symptoms (LUTS) referred to urodynamic study (UDS). All patients self-answered the International Prostate Score Symptoms (IPSS) questionnaire. After the UDS, the bladder was filled with 150 mL to determine UEBW. • Patients with a bladder capacity under 150 mL, a previous history of prostate surgery or pelvic irradiation, an IPSS score <8, a bladder stone or urinary tract infection were excluded. • After a pressure-flow study, the Schafer linear passive urethral resistance relation nomogram was plotted to determine the grade of obstruction: Grades I-II/VI were defined as mild obstruction, Grades III-IV/VI as moderate obstruction, and Grades V-VI/VI as severe obstruction.

• The UEBW was 51.7 ± 26.9, 54.1 ± 30.0 and 54.8 ± 28.2 in patients with mild, moderate and severe BOO, respectively (P= 0.130). The UEBW allowed us to define four groups: (i) UEBW <35 g; (ii) 35 g ≤ UEBW < 50 g; (iii) 50 g ≤ UEBW < 70 g; and (4) UEBW ≥ 70 g. • We did not find any differences in age, prostate weight, IPSS, PVR, cystometric bladder capacity, presence of detrusor overactive and degree of obstruction in the aforementioned groups.

• Despite the fact that some studies have emphasized the value of UEBW as an efficient non-invasive method for evaluating lower urinary tract obstruction, our study suggests that UEBW does not present any individual correlation with LUTS or objective measurements of BOO.