Intravesical prostatic protrusion is a risk factor for bladder stone in patients with benign prostatic hyperplasia.

OBJECTIVE: To assess the risk factor that influences bladder stone formation in patients with benign prostatic hyperplasia (BPH).

MATERIALS AND METHODS: We reviewed the data of 271 consecutive patients with BPH who underwent transurethral resection of the prostate between January 2008 and December 2012. Patients were classified into 2 groups based on the presence of a bladder stone: Group 1 had a bladder stone and group 2 did not. Univariate analysis was performed to determine the association between the presence of bladder stone and the patients' age, body mass index, International Prostate Symptom Score, total prostate volume (TPV), transitional zone volume, intravesical prostatic protrusion (IPP), uroflow parameters, and urodynamic parameters.

RESULTS: The overall rate of bladder stone in patients with BPH was 9.9%. The patients' body mass index, International Prostate Symptom Score, and urodynamic parameters did not significantly differ between the 2 groups. The patients' age, TPV, transitional zone volume, and IPP were all significantly higher and the Qmax was significantly lower in group 1 than that in group 2. Multivariate analysis revealed that age (hazard ratio [HR] = 1.089; P = .020), IPP (HR = 1.145; P <.001), and Qmax (HR = 0.866; P = .019) significantly affected the presence of bladder stone in patients with BPH. A predictive model using logistic regression for bladder stone in BPH patients was defined as follows: probability = 1/[1 + exp (-8.499 + 0.085 (age) + 0.009 (TPV) + 0.136 (IPP) - 0.143 (Qmax))] with area under the curve of 0.850 obtained from the receiver operating characteristic curve analysis.

CONCLUSION: This study demonstrated that older age, longer IPP, and lower Qmax are independent factors that associated with the presence of bladder stone in patients with BPH.