OBJECTIVETo identify the correlation of the volume of residual urine (VRU) with the severity of bladder outlet obstruction (BOO) and detrusor contractility in patients with benign prostatic hyperplasia (BPH).

METHODSA total of 152 patients with clinically diagnosed BPH underwent ultrasonography for measurement of the prostate volume and RVU, free uroflowmetry, and urodynamic examination for the severity of BOO and detrusor contractility. Using the software SPSS20. 0, we analyzed the correlation between the ultrasonographic results and urodynamic parameters and compared the two sample means by the t-test.

RESULTSThe prostate volume was correlated positively with BOO severity (r = 0.432, P < 0.01) and detrusor contractility (r = 0.343 , P < 0.01) while Qmax negatively with BOO severity (r = 0.327, P < 0.01) but not significantly with detrusor contractility (r = 0.123, P > 0.05). VRU showed a significantly negative correlation with detrusor contractility when > 150 ml (r = -0.490, P < 0.01), even more significantly when > 300 ml (r = -0.717, P < 0.01), but exhibited no significant correlation with it when ≤ 150 ml (r = 0.041, P > 0.05).

CONCLUSIONVRU can somehow predict the detrusor function. For patients with VRU > 150 ml, especially for those with VRU > 300 ml, the detrusor function should be evaluated and urodynamic examination is recommended for exact assessment of BOO severity and detrusor contractility.