Hypothesis / aims of study
Although post-micturition dribble (PMD) is a common and bothersome symptom, the frequency and factors involved are not well understood. We investigated the frequency and pathogenesis of PMD from a urodynamic perspective in men with lower urinary tract symptoms (LUTS) in clinical practice.
Study design, materials and methods
This study included treatment-naïve men aged ≥40 years, who visited our hospital with a chief complaint of LUTS (international prostate symptom score [IPSS] total score of ≥8) and underwent urodynamic studies (UDS), including cytometry and pressure-flow study. PMD was assessed by adding the following question to the IPSS: “Over the last month, how often did you experience dribbling after voiding and got your underwear wet?”. Patients who answered "not at all" to this question were defined as those without PMD (the PMD-free group), and those who answered "more than half the time" or " almost always" were defined as those with PMD (the PMD group).
This study focused on the detrusor pressure after voiding and calculated the time to return to the pre-voiding pressure (defined as “recovery time to baseline detrusor pressure”), as shown in the Figure. Patient characteristics and UDS parameters, including recovery time to baseline detrusor pressure, were compared between the two groups.
Results
Of the 739 patients analyzed, 81 (11.0%) were classified into the PMD group and 167 (22.6%) into the PMD-free group. Although there were no significant differences in age or prostate volume between the two groups, the PMD group had significantly higher subjective symptoms such as IPSS, overactive bladder symptom score (OABSS), and IPSS-quality of life score. UDS parameters of voiding function, including maximum flow rate and bladder outlet obstruction index, showed no difference, whereas the bladder capacity was significantly smaller and the frequency of detrusor overactivity was significantly higher in the PMD group. Notably, the mean recovery time to baseline detrusor pressure in the PMD group was 47.9 seconds, which was significantly longer than that in the PMD-free group (14.7 seconds, p <0.001). Multivariate regression analysis revealed that a longer recovery time to baseline detrusor pressure was significantly associated with the occurrence of PMD (Table).
Interpretation of results
Although it has been thought that PMD is caused by trapped urine in the bulbar urethra due to the weakening of pelvic floor muscle such as bulbocavernosus muscle, delayed return of detrusor contraction to baseline also may have caused PMD. The exact mechanism by which this causes PMD is unknown, but it is possible that prolonged detrusor contractions after voiding leads to inadequate closure of the urethral sphincter, resulting in influx of urine into the bulbar urethra.