Post-void residual (PVR) urine is a common part of the routine clinical assessment in males with lower urinary tract symptoms (LUTS). Aim of this study was to assess the clinical role, the values, and the correlation with other main pre-operative examinations of the pre-operative PVR in males underwent transurethral resection of the prostate (TURP) and the related outcomes after the procedure.

This was a prospective study involving males with LUTS candidates for TURP. Patients underwent medical and urological history. Both pre-operative evaluation and the 2-year follow-up consisted in: peak flow (Qmax), PVR, PVR-ratio as the ratio of PVR to bladder volume (BV: voided volume (VV) + PVR), and the International Prostate Symptoms Score (IPSS) Questionnaire. Patients were also distributed in 5 groups, according to pre-operative PVR thresholds: i) PVR 0-50ml; ii) PVR 51-100ml; iii) PVR 101-150ml; iiii) PVR 151-200ml; iiiii) PVR>200ml. Statistical analysis was performed using T-test, Wilcoxon test, one-way ANOVA test, Kruskal-Wallis Test.

Patients enrolled in the study were 100 (mean±SD age: 68.8±8.7 yrs). At baseline, 38/100 patients (38%) showed a PVR <50 ml, in 62/100 patients (62%) the PVR was <100 ml, while 37/100 patients (37%) had a PVR between 51-150 ml and 25/100 patients (25%) a PVR >150 ml. A significant improvement in VV, Qmax, PVR and IPSS score (p<0,001) was documented in all patients (Table 1). No significant difference was found in Qmax and IPSS score among the groups, in both pre-operative and post-operative assessment. In each group we found a significant improvement in Qmax and IPSS score after prostate resection, particularly in PVR <150 ml or >200 ml (p<0,001; Table 2). Table 2 shows how PVR decreased significantly after TURP in all the groups except in the Group i (PVR 0-50ml). This finding may be related to the low pre-operative PVR.

This study demonstrated the controversial clinical role of pre-operative PVR. Indeed, the majority of the candidates for TURP showed a low pre-operative PVR (<100 ml), despite both pre-operative uroflowmetry and IPSS score were pathological. Thus, pre-operative PVR was poorly correlated to micturition patterns and to urinary symptoms. Males underwent prostate resection notwithstanding the low values of pre-operative PVR, and therefore uroflowmetry outcomes and urinary symptoms had the main influence on the clinical decision-making. Furthermore, the patient’s outcomes at 2-years follow-up were not affected by the pre-operative values of PVR, and Qmax and IPSS score improved after TURP regardless of pre-operative PVR. This finding suggests that PVR may be not always correlated to voiding dysfunctions and should be considered only as one part of the examinations of the pre-operative assessment of the males with LUTS. On the other hand, it is remarkable that the PVR volumes, when pre-operatively higher than 50 ml, always decreased after TURP and that the mean post-operative PVR lowered to less the 50 ml. Thus, in patients with no more bladder outlet obstruction, mean PVR was less than 50 ml, regardless of the amount of the pre-operative PVR. This data may indicate that patients with pre-operative PVR higher than 50 ml may be at risk of voiding dysfunctions, but that the severity of voiding dysfunctions is not correlated to the higher PVR volumes. Further data are needed to confirm this finding.

Pre-operative PVR is a controversial clinical parameter in the assessment of men with LUTS. Only a minor part of the candidates for TURP showed a high pre-operative PVR. Pre-operative PVR did not significantly influenced prostate resection outcomes and was poorly correlated to pre-operative micturition patterns and urinary symptoms. Thus, this parameter should be considered only as one part of the pre-operative investigations in the assessment of the males with LUTS. Mean PVR decreased after prostate resection, and our data suggest that a PVR higher than 50 ml could be a sign of pathological bladder emptying, but that higher volumes of pre-operative PVR are not correlated to the severity of the disease. Further data are needed to confirm this finding.