Non-invasive evaluation of bladder outlet obstruction in benign prostatic hyperplasia: a clinical correlation study

Objectives: To determine the utility of ultrasonography (US)-derived parameters (e.g. prostate volume [PV], bladder wall thickness [BWT], post-void residual urine volume [PVR], and intravesical prostatic protrusion [IPP]) and uroflowmetry for identifying bladder outlet obstruction (BOO) by correlating them with the results of pressure–flow urodynamic studies (UDS). Patients and methods: In all, 164 patients presenting with lower urinary tract symptoms suggestive of benign prostatic hyperplasia (BPH), from May 2016 to December 2018, were included in this study. All had International Prostate Symptoms Score (IPSS), Quality-of-Life (QOL) index, uroflowmetry (including maximum urinary flow rate [Q(max)]) and PVR measured by transabdominal US. Pressure–flow UDS were performed on all men and BOO was defined by a BOO Index (BOOI) >40. Men with a Q(max) of ≥12.0 mL/s were considered to have ‘good’ flow. Results: Amongst the 164 men, the mean (SD) age, PV, BWT and Q(max) were 66.72 (9.88) years, 51.91 (13.24) mm, 5.07 (0.91) mm, and 8.46 (3.59) mL/s, respectively. In all, 91 (55.49%) patients had BOO with a BOOI >40 and nine (5.49%) had equivocal BOO with a BOOI of 20–40. The IPP was a statistically significant predictor (P < 0.001) of BOO compared with other variables in the initial evaluation. In patients with BOO confirmed by the pressure–flow UDS, IPP Grade III was associated with a higher BOOI than was Grade I and II (P < 0.001). Conclusion: BWT, PV and PVR in conjunction with IPP are good predictors of clinically significant BOO due to BPH. Abbreviations: AUC: area under the curve; BOOI: BOO Index; BPO, benign prostatic obstruction; BWT, bladder wall thickness; IPP: intravesical prostatic protrusion; P(det): detrusor pressure; PV: prostate volume; PVR: post-void residual urine volume; Q(max): maximum urinary flow rate; QOL: quality of life; ROC: receiver operating characteristic; (TA)US: (transabdominal) ultrasonography; UDS: urodynamic studies