INTRODUCTION
Postmicturition dribbling (PMD), which is distinct from terminal dribbling, is defined as the involuntary loss or leakage of urine immediately after voiding has ended, typically after leaving the toilet in men or after rising from the toilet in women [1]. PMD was historically considered to have a low prevalence [2]. However, recent studies have reported prevalence rates of 10%– 50%, depending on the study population and the definitions used [3-5]. PMD is reported more frequently in Asian countries [6-8] and tends to increase with age [7, 9].
The International Prostate Symptom Score (IPSS) is widely used to assess lower urinary tract symptoms (LUTS) in men [10]. However, PMD is typically assessed using less commonly used questionnaires [11-13]. Despite its omission from the IPSS, PMD can be as bothersome as other LUTS, and more than half of affected men report substantial distress [6, 14].
PMD is thought to result from residual urine in the bulbar or prostatic urethra after voiding. Conservative interventions, such as urethral milking and pelvic floor muscle exercises, have shown some effectiveness [15]. Recent studies have also supported the use of phosphodiesterase type 5 inhibitors, such as tadalafil and udenafil, to reduce PMD severity and improve quality of life [16, 17].
To further clarify the pathophysiology of PMD, this study examined the clinical characteristics, urodynamic study (UDS) findings, and transrectal ultrasound of the prostate (TRUSP) findings in men with refractory LUTS.
MATERIALS AND METHODS
Patient Population
From 2008 to 2010, this cross-sectional study enrolled male patients with LUTS that were refractory to standard lifestyle modifications and pharmacological treatment, including α-blockers, antimuscarinics, or β3-adrenoceptor agonists, at a tertiary center in Taipei, Taiwan. Participants completed a comprehensive questionnaire and underwent TRUSP and UDS. Patients with a history of genitourinary tract surgery were excluded.
This study was approved by the institutional review board of National Taiwan University Hospital (202102073RINC). The requirement for informed consent was waived, and all procedures followed institutional guidelines.
Questionnaire
Participants completed a self-administered questionnaire that collected data on baseline characteristics, including age, body weight, height, and waist and hip circumference; LUTS; lifestyle factors; comorbidities; medication use; and the impact of LUTS. PMD was assessed using a 6-point Likert scale: 0=never, 1=seldom, 2=once daily, 3=less than half of voids, 4=more than half of voids, and 5=every void. A score ≥3 was considered to indicate clinically significant PMD. Other LUTS, including frequency, urgency, incomplete emptying, intermittency, weak stream, abdominal straining, hesitancy, pelvic pain, urge urinary incontinence, stress urinary incontinence, and nocturnal enuresis, were rated on a Likert scale from 0 (never) to 5 (almost always). Nocturia was assessed as the number of times a patient woke at night to void. Quality of life affected by LUTS was rated from 0 (delighted) to 6 (terrible). The storage symptom score was defined as the sum of the scores for frequency, urgency, and nocturia, whereas the voiding symptom score was defined as the sum of the scores for weak stream, intermittency, abdominal straining, and incomplete emptying.
Lifestyle variables were assessed as follows. Sleep quality was rated from 1 (very poor) to 5 (very good). Exercise was scored as 0 (never), 1 (seldom), or 2 (usually). Life stress was rated from 0 (no stress) to 3 (severe stress), and self-assessed health status was rated from 1 (terrible) to 5 (great). Alcohol consumption was rated as 0 (never), 1 (seldom), or 2 (usually). Smoking was assessed as 0 (never), 1 (less than 1 pack per week), or 2 (more than 1 pack per week). Comorbidities and medication use were obtained from the questionnaire and defined as diseases present within the preceding year or medications used within the preceding year. The impact of LUTS on motivation, daily life, including daily activities, fluid intake, and long-distance travel, psychological well-being, including anxiety and distress, and interpersonal relationships, including family and sexual partner relationships, was rated on a scale from 0 (no impact) to 4 (very severe impact).
UDS and TRUSP
All patients underwent multichannel urodynamic studies according to International Continence Society standards. The protocol included pre- and post-pressure-flow uroflowmetry to assess voided volume and maximum flow rate (Qmax). Filling cystometry and pressure-flow studies were performed using a double-lumen transurethral catheter and a rectal balloon catheter to measure intravesical and abdominal pressure, respectively. Saline was infused at room temperature at a medium filling rate of 30–50 mL/min, and bladder sensation, compliance, detrusor overactivity (DO), and cystometric capacity were recorded. The pressure-flow phase was initiated when the patient reported a strong desire to void.
TRUSP was used to measure prostate and adenoma volumes with the ellipsoid formula (length×width×height×0.52). The prostatic urethral angle (PUA) was defined as the angle formed by the proximal and distal prostatic urethra. Intravesical prostatic protrusion (IPP) was graded according to the distance from the tip of the protruding prostate to the bladder neck: grade 0, 0 mm; grade 1, <5 mm; grade 2, 5–10 mm; and grade 3, >10 mm [18]. All imaging and urodynamic interpretations were reviewed by Yu et al.
Statistical Analysis
Continuous variables were compared using the Wilcoxon ranksum test or Kruskal-Wallis test, and categorical variables were compared using the chi-square test. Multivariable logistic regression with forward stepwise selection was used to evaluate associations with PMD. The Wald test was used to assess the significance of the odds ratio (OR) for each parameter in the regression model. A P-value <0.05 was considered statistically significant. Analyses were performed using R ver. 4.1.0 (R Foundation for Statistical Computing, Austria).
RESULTS
Baseline Characteristics
A total of 150 male patients were enrolled. The mean age was 64.7 (range, 32–91) years, the median IPSS was 20, and the median prostate volume (PV) was 29.8 (range, 6.5–334) mL. PMD was reported by 71 patients (47%). Most baseline characteristics were similar between the 2 groups, although patients with PMD were more likely to consume alcohol. No comorbidity or specific medication use was significantly associated with PMD (Table 1). In the subgroup with severe IPSS, PMD prevalence was higher (67%), and similar findings were observed. However, patients with PMD were slightly older than those without PMD, although the difference did not reach statistical significance (67.0 years vs. 61.6 years, P=0.06) (Supplementary Table 1).
Forward regression analysis showed that, among baseline characteristics, comorbidities, and medication use, better selfassessed health status was associated with a 50% reduction in the odds of PMD, and prokinetic drug use was associated with a 68% reduction in the odds of PMD (Table 2).
Association With LUTS
Patients with PMD had more severe storage symptoms (9.3 vs. 6.8, P<0.001) and voiding symptoms (15.1 vs. 9.1, P<0.001), as well as higher total IPSS scores (24.4 vs. 15.9, P<0.001). Nocturia was the only IPSS item that did not differ significantly between the 2 groups. Quality-of-life scores tended to be worse in the PMD group (5.0 vs. 4.6, P=0.051), although the difference did not reach statistical significance. Patients with PMD also tended to report more hesitancy, lower abdominal pain, and urge urinary incontinence, but not stress urinary incontinence (Table 3). Multivariable analysis showed that urgency, incomplete emptying, and weak stream were strong independent predictors of PMD, with ORs of approximately 1.5 (Fig. 1).
Impact on Quality of Life
Patients with PMD tended to report worse LUTS-related quality of life than patients without PMD, although the difference was of borderline statistical significance (5.0 vs. 4.6, P=0.051) (Table 3). PMD also affected several aspects of daily life, particularly motivation, daily activities, sexual life, and psychological well-being, including anxiety and distress (Table 4).
UDS and TRUSP
Patients in both groups had poor Qmax (10.2 vs. 11.0, P=0.567). The proportion of patients with DO was approximately 20% in both groups (phasic DO, 23% vs. 22%; terminal DO, 24% vs. 27%). The bladder outlet obstruction index (BOOI) was numerically higher in the PMD group (34.5 vs. 29.9, P=0.287), but the proportion of patients with bladder outlet obstruction (BOO) did not differ significantly between groups (42% vs. 30%, P=0.179). Detrusor underactivity was uncommon in both groups (6% vs. 9%, P=0.658). Among all urodynamic and TRUSP parameters, only bladder compliance dif-fered significantly between groups, with poor compliance more frequent in patients with PMD (17% vs. 4%, P=0.016) (Table 5). Multivariable logistic regression showed that poor compliance was associated with a more than four-fold increase in the odds of PMD (Fig. 2). Prostate and adenoma volumes were similar between the 2 groups (37.4 vs. 37.6, P=0.276; 17.9 vs. 17.1, P=0.296). IPP and the PUA also did not differ between the 2 groups.
In the severe IPSS subgroup, patients had low Qmax in both groups (9.7 vs. 9.8, P=0.746). Patients with PMD had significantly lower bladder capacities than those without PMD (276 mL vs. 329 mL, P=0.038). Bladder compliance did not differ significantly between groups, and the other parameters showed findings similar to those in the overall cohort (Supplementary Table 2).
DISCUSSION
This is the first study to incorporate both UDS and TRUSP to comprehensively evaluate surgery-naive men with PMD. PMD was present in 47% of this medication-refractory LUTS cohort and in 67% of patients with severe IPSS. PMD was significantly associated with higher total IPSS scores and with most LUTS. Although PMD is not included in the IPSS, it had a comparable adverse effect on quality of life, particularly in domains such as motivation, daily activity, sexual function, and psychological well-being. Among all UDS and TRUSP parameters evaluated, poor bladder compliance was significantly more common in patients with PMD.
Population-based studies have shown that the prevalence of PMD is approximately 5.5%–16.5%, depending on the definitions used [2-4, 19]. However, among symptomatic men seeking care for LUTS, prevalence can exceed 40% [9, 15, 20]. In this hospital-based cohort of patients with medication-refractory LUTS, PMD prevalence was even higher and exceeded twothirds among patients with severe LUTS (IPSS >20) (Supplementary Table 1). Despite its high prevalence, PMD is often overlooked by clinicians and researchers, possibly because it is frequently attributed to aging or assumed to be less bothersome than other LUTS [12, 16]. However, recent evidence suggests that PMD can substantially affect quality of life [7, 16] and may respond to conservative or pharmacological treatment [15].
PMD rarely occurs in isolation and frequently coexists with other LUTS [3, 16], particularly voiding symptoms. Prior studies have consistently shown strong associations between PMD and voiding symptoms such as incomplete emptying, weak stream, and intermittency [2, 4, 9]. These findings are consistent with the present results, in which urgency, incomplete emptying, and weak stream were the LUTS most strongly associated with PMD. Although PMD was more consistently asso-ciated with voiding symptoms, PMD has also been linked to storage symptoms such as urgency and frequency [21], possibly because residual urine stimulates afferent C-fiber pathways and triggers DO [22, 23]. In this analysis, urgency was independently associated with PMD, supporting the potential contribution of storage dysfunction to its pathophysiology. These overlapping symptoms may increase distress and indicate that PMD should be included in comprehensive LUTS assessment, particularly given its effect on quality of life.
PMD has also been reported to increase with age, particularly after age 50 years [3, 9], a trend that was observed in this cohort, although the age difference did not reach statistical significance. Lifestyle factors such as smoking and alcohol consumption have previously been associated with LUTS, including PMD [19]. In this study, regular alcohol consumption was independently associated with PMD, whereas smoking was not. Although LUTS have been associated with cardiovascular, metabolic, and neurological disorders, including diabetes mellitus, in prior studies [19, 24-27], no significant associations between PMD and comorbidities were identified in this cohort. This discrepancy may reflect the cross-sectional study design or the possibility that some patients had not yet developed these conditions. Longer-term follow-up would help clarify these potential associations.
Video urodynamic studies have shown that PMD involves residual urine pooling in the bulbar or prostatic urethra after voiding [28]. One study found that PMD was associated with absent postvoid urethral milking, a video urodynamic finding that reflects urethral peristalsis [29]. However, this mechanism may not explain all cases, because not all patients respond to urethral milking or pelvic floor therapy [15]. Transrectal ultrasound is one of the most commonly used examinations for evaluating male LUTS. Although some studies have linked PMD to increased PV, suggesting a possible role for BOO-targeted therapy, other studies have found no such association [7, 21]. The present findings support the latter interpretation, because no significant relationship between PV and PMD was observed. Similarly, other TRUSP-derived parameters, such as PUA and IPP, which have previously been associated with worse IPSS [18], were not significantly associated with PMD in this cohort. Whether decreased peak urinary flow is associated with PMD remains unclear [7, 9]. One Japanese study that focused on pressure-flow findings in patients with PMD reported that the BOOI was positively associated with PMD (50.3 vs. 65.6, P=0.02), suggesting that functional BOO may contribute to residual urine in the urethra. However, the present study showed no significant difference in BOOI between patients with and without PMD (34.5 vs. 29.9, P=0.287), and the absolute BOOI values were lower than those reported in the Japanese study. This difference may reflect the younger age and smaller PV of the present cohort. Poor compliance was more common in the PMD group (17% vs. 4%, P=0.016) and was associated with PMD in multivariable regression analysis (OR, 4.57; 95% confidence interval, 1.13–18.56; P=0.034). Poor compliance has been associated with neurological conditions [30, 31], and a video UDS showed increased PMD prevalence accompanied by impaired postvoid urethral milking after radical prostatectomy [29]. Therefore, PMD may be associated with neurological deficits in some patients. In addition, the presence of PMD may indicate greater LUTS severity, which may also correlate with poor compliance.
This study has several limitations. First, its cross-sectional design limits causal inference regarding associations between clinical parameters and the presence of PMD. Second, the absence of objective measurements of PMD volume may have reduced the accuracy of symptom severity assessment. Third, video urodynamic studies were not performed. Finally, because the study was conducted at a tertiary care center, the findings may not be generalizable to broader populations. Future prospective studies should include larger patient populations and validate bladder compliance as a predictive marker for PMD. The potential role of PMD as an early indicator of long-term outcomes, such as progression to surgical intervention and major organ dysfunction involving cardiovascular disease, neurological decline, or kidney dysfunction, should also be explored.
In conclusion, no urodynamic or TRUSP abnormality other than poor bladder compliance was associated with PMD in men with LUTS. Although PMD significantly impaired quality of life, it is not included in the IPSS, suggesting that the IPSS may not fully capture the range of symptoms experienced by men with LUTS.
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