INTRODUCTION
Benign prostate obstruction (BPO), caused by benign prostatic enlargement, is a major contributor to male lower urinary tract symptoms (LUTS) and substantially impairs quality of life. In addition, BPO can lead to urinary retention, obstructive uropathy, recurrent urinary tract infections, and bladder stones [1]. Prostate deobstruction operations, including transurethral resection of the prostate (TURP), GreenLight laser photoselective vaporization of the prostate (GLPVP), and holmium laser enucleation of the prostate (HoLEP), are widely used and effective treatment options in urological practice [2-4]. After these procedures, a Foley catheter is placed for a short period before removal. However, a subset of patients experience failure of the initial trial without catheter (TWOC), necessitating recatheterization. This event imposes multiple burdens, including prolonged hospitalization, increased risk of urinary tract infections, psychological stress, and additional follow-up visits or readmissions [5,6], which differ from the chronic implications associated with long-term catheterization. Therefore, identifying predictors of initial TWOC failure is essential for optimizing perioperative care.
Several factors, including postvoid residual (PVR) urine volume [7,8], prostate volume [9], timing of TWOC [10], age [11], and diabetes mellitus (DM) [12], have been associated with initial TWOC failure after prostate deobstruction surgery. However, studies have reported inconsistent predictive factors and cutoff values. Compared with these indirect parameters, multichannel urodynamic studies, which are specifically designed to evaluate lower urinary tract dysfunction, offer more precise assessments [13]. Nonetheless, no previous study has directly examined the value of multichannel urodynamic parameters in predicting initial TWOC failure after prostate deobstruction surgery. Furthermore, despite guideline-based indications for preoperative urodynamic studies [1], strategies for risk-stratifying initial TWOC failure in this clinical setting remain unaddressed. We therefore hypothesize that multichannel urodynamic parameters may serve as more accurate predictors of initial TWOC failure. This study aims to identify predictors of initial TWOC failure by integrating multichannel urodynamic parameters with traditionally recognized clinical factors.
MATERIALS AND METHODS
Study Design and Patient Selection
We retrospectively reviewed patients who underwent TURP, GLPVP, and HoLEP for BPO at National Cheng Kung University Hospital between March 2018 and September 2024. Among these, patients who had undergone preoperative multichannel urodynamic studies within 1 year before surgery were included. Urodynamic studies were performed in patients who met at least 1 of the following criteria, consistent with guideline recommendations: previous unsuccessful invasive treatment for LUTS; inability to void more than 150 mL; bothersome predominantly voiding LUTS with maximum flow rate (Qmax) >10 mL/sec; PVR >300 mL; age >80 years or <50 years; or when additional evaluation of the underlying pathophysiology was required before invasive intervention [1]. Patients were excluded if they had a history of malignancy (prostate or bladder cancer), urethral stricture, neurologic conditions (Parkinson disease, stroke, dementia, spinal cord injury), spine-related disorders (chronic low back pain or sciatica-related radiculopathy), or prior pelvic irradiation or lower urinary tract surgery [14,15]. Data from preoperative assessments, including patient characteristics, biochemical studies, transrectal ultrasound of the prostate, uroflowmetry and PVR, and multichannel urodynamics, were collected for analysis. The study was approved by the Institutional Review Board of National Cheng Kung University Hospital (IRB number: B-ER-113-234).
Urodynamic Studies
Multichannel pressure-flow studies were performed preoperatively in accordance with the International Continence Society (ICS) Good Urodynamic Practices [16]. At our institution, urodynamic testing is consistently conducted by YCO and YLK and is routinely performed for patients considered for prostate deobstruction surgery when clinically indicated, following European Association of Urology guideline-based criteria.
Urodynamic studies were performed after removal of the indwelling catheter, if present, using a 6Fr double-lumen transurethral catheter to measure intravesical pressure and a fluidfilled rectal balloon catheter to record abdominal pressure. The bladder was filled with normal saline at room temperature at a physiological rate of 30 mL/min. Parameters assessed included bladder compliance, cystometric capacity, voided volume (VV), PVR, Qmax, and detrusor pressure at Qmax (PdetQmax). Bladder capacity was calculated as the sum of VV and PVR, and voiding efficiency was defined as VV divided by bladder capacity.
To quantify detrusor function and outlet resistance [13], we calculated the bladder contractility index (BCI=PdetQmax+5×Qmax) and the bladder outlet obstruction index (BOOI=PdetQmax–2×Qmax) using ICS-recommended formulas. BOOI was categorized as high (≥40 cm H2O), equivocal (20–40 cm H2O), or low (<20 cm H2O). Detrusor underactivity (DU) was defined as BCI<100 cm H2O in the presence of a BOOI <20 cm H2O to avoid misclassification of masked obstruction. These definitions and thresholds were explicitly applied and are consistent with current ICS guidance.
Operations and Outcome Measurements
All procedures were performed by board-certified urologists who had each surpassed case-volume thresholds generally accepted to ensure procedural proficiency. Bipolar TURP was performed with the Olympus Bipolar TURP System (Olympus Corp., Japan) by 8 high-volume surgeons. Laser-based operations have been routine at our center since 2013. GreenLight XPS 180-W photoselective vaporization of the prostate (GLPVP) was performed using the GreenLight XPS Laser System (Boston Scientific, USA); 153 of the 166 GLPVP procedures (92.2%) were conducted by 3 dedicated laser surgeons (YCO, YLK, and YSC), while the remaining 13 were performed by 5 additional consultants. HoLEP was performed using the Cyber Ho Holmium Laser System (Quanta System S.p.A., Italy), and 22 of the 23 procedures (95.7%) were performed by a single experienced surgeon (YLK), ensuring technical consistency. Surgical modality was determined through shared decision-making between the surgeon and patient, taking into account surgeon experience with each technique, patient preference, prostate size, and comorbidities.
All surgeons adhered to an institution-wide perioperative protocol that standardizes anesthesia, antibiotic prophylaxis, and postoperative catheter care using a 22Fr 3-way Foley catheter with continuous bladder irrigation for 12–24 hours. The initial TWOC was routinely scheduled on postoperative day (POD) 2 across all surgical modalities, provided that the urine was clear and no active bleeding was present. In cases of persistent hematuria, specific comorbidities, or at the surgeon’s discretion, TWOC was postponed. In rare instances, when clinically appropriate and at the patient’s request, TWOC was performed on POD 1.
The primary endpoint was initial TWOC failure, defined as the need for recatheterization within 7 days of catheter removal. Recatheterization was defined as follows: prior to discharge, patients underwent PVR assessment after catheter removal. If they were unable to void, had voiding efficiency <50% with persistent bladder distension and discomfort, or had sustained PVR >200 mL, a catheter was reinserted. Within 7 days after discharge, any patient who returned with voiding difficulty, was diagnosed with urinary retention, and underwent catheter reinsertion was also considered to have experienced TWOC failure. Secondary endpoints included postoperative urodynamic parameters and long-term TWOC failure. Uroflowmetry and PVR were reassessed 3 months after surgery.
Statistical Analysis
Statistical analysis was performed using IBM SPSS Statistics ver. 25.0 (IBM Co., USA). Continuous variables were reported as means±standard deviation, and categorical variables as frequencies and percentages. Between-group comparisons were conducted using the Kruskal-Wallis and Mann-Whitney Utests for continuous variables and chi-square or Fisher exact tests for categorical variables. The paired t-test was used to evaluate within-group differences before and after surgery. Univariate logistic regression was used to screen potential predictors of initial TWOC failure. Variables with P<0.20, along with clinically relevant factors, were included in a multivariate logistic regression model, with results presented as odds ratios (ORs) and 95% confidence intervals (CIs). Collinearity diagnostics were performed to assess multicollinearity among predictors. A sensitivity analysis excluding the HoLEP group was conducted because of its relatively small sample size. A P-value <0.05 was considered statistically significant.
RESULTS
Baseline Characteristics of Patients Undergoing Prostate Deobstruction Surgery
A total of 327 male patients who underwent prostate deobstruction surgery were included in this study (Table 1). The mean age was 69.41±10.48 years, the mean prostate volume was 64.5±38.5 mL, and the mean International Prostate Symptom Score was 19.91±6.81. The surgical distribution consisted of 138 patients (42.2%) who underwent TURP, 166 (50.8%) who underwent GLPVP, and 23 (7.0%) who underwent Ho-LEP. Among all patients, 41 (12.5%) had urinary catheterization before surgery, and 69 (21.3%) had PVR >300 mL. Comorbidities included DM in 28.9% of patients and chronic kidney disease in 17.9%. In addition, urinary tract infection occurred in 6.2% of patients following multichannel urodynamic studies.
Changes in Uroflowmetry and Voiding Parameters After Surgery
Postoperatively, significant improvements in uroflowmetry parameters were observed across all surgical groups (Table 2). The mean Qmax increased from 7.4±5.0 mL/sec preoperatively to 16.6±9.9 mL/sec postoperatively (P<0.001). The mean PVR decreased from 139.5±151.1 mL to 43.3±62.2 mL (P<0.001), and voiding efficiency significantly improved from 50.8%± 34.5% to 81.1%±23.5% (P<0.001). Subgroup analyses revealed that all 3 surgical modalities each resulted in significant increases in Qmax and reductions in PVR (all P<0.001).
Comparison of Initial TWOC Success and Failure Groups
Among the overall cohort, 41 patients (12.5%) experienced initial TWOC failure (Table 3). Preoperative PVR was significantly higher in the TWOC failure group compared with the success group (195.5±220.0 mL vs. 131.7±137.7 mL, P=0.017). The prevalence of urinary catheterization before surgery was also higher in the TWOC failure group (24.4% vs. 10.8%, P=0.014).
Regarding urodynamic parameters, the prevalence of DU was significantly higher in the TWOC failure group (69.2% vs. 40.5%, P<0.001), whereas the proportion of patients with high BOO was significantly lower in the failure group compared with the success group (53.8% vs. 72.0%, P=0.020). In contrast, patients with low BOO were more likely to experience initial TWOC failure (17.9% vs. 6.7%, P=0.015). TWOC failure rates did not differ significantly between the early (≤2 days, 11.6%) and late (>2 days, 15.1%) removal groups (P=0.400). Longterm TWOC failure occurred in 3 patients (7.3%) within the initial TWOC failure group, whereas no cases occurred in the initial TWOC success group (P<0.001). Among patients who initially failed but subsequently passed TWOC, the average time to successful catheter removal was 8.3 days postoperatively.
Predictors of Initial TWOC Failure
In univariate logistic analysis (Table 4), DU was significantly associated with an increased risk of initial TWOC failure (OR, 3.449; 95% CI, 1.685–7.061; P<0.001). Likewise, patients with low BOO had an increased likelihood of failure (OR, 3.051; 95% CI, 1.191–7.818; P=0.020). A higher PVR (>300 mL) was also associated with an increased risk of initial TWOC failure (OR, 2.149; 95% CI, 1.057–4.370; P=0.035).
In multivariate analysis, DU remained a significant predictor of initial TWOC failure (OR, 2.773; 95% CI, 1.256–6.124; P=0.012), as did low BOO (OR, 2.881; 95% CI, 1.045–7.943; P=0.041). However, PVR >300 mL was no longer significant after adjustment (P=0.227). Other variables, including age, prostate volume, and comorbidities, were not significant predictors. Sensitivity analysis excluding HoLEP confirmed DU and low BOO as consistent predictors (Supplementary Table 1). No significant multicollinearity was detected, with all variance inflation factor values below 2.0 (Supplementary Table 2).
Initial TWOC Failure Across Different Urodynamic Patterns
Fig. 1 illustrates the association between urodynamic patterns and initial TWOC failure. Patients with DU and low BOO demonstrated the highest risk of TWOC failure (OR, 4.560; 95% CI, 1.696–12.262; P=0.003), whereas those with high BOO but no DU had a significantly lower risk (OR, 0.321; 95% CI, 0.151–0.684; P=0.003). In subgroup analysis, among patients with PVR ≥300 mL, those with high BOO but preserved detrusor contractility had a significantly lower risk of initial TWOC failure (OR, 0.110; 95% CI, 0.013–0.913; P=0.041). A similar trend was observed in the PVR ≥200 mL subgroup (OR, 0.154; 95% CI, 0.033–0.727; P=0.018).
DISCUSSION
Prostate deobstruction operations, including TURP, GLPVP, and HoLEP, effectively alleviate LUTS caused by BPO. However, a subset of patients still experience initial TWOC failure postoperatively, with a failure rate of 12.5% in this cohort. DU (BCI<100) and low BOO (BOOI<20) emerged as independent risk factors, contrasting with previous studies that emphasized high preoperative PVR. Importantly, this is the first study to demonstrate that even patients with high PVR or preoperative catheterization may still achieve successful TWOC if they exhibit preserved detrusor function and high BOO. This finding highlights the distinct value of multichannel urodynamic studies in refining initial TWOC risk stratification before prostate deobstruction surgery, especially for identifying high-PVR patients who may safely undergo earlier catheter removal. As such, these data support more individualized postoperative decision-making.
Optimizing the timing of initial TWOC after prostate deobstruction surgery is essential. Prolonged catheterization increases discomfort, infection risk, and the likelihood of urethral stricture formation [17], whereas premature removal can result in retention due to capsular edema or clot formation [9]. Historically, catheter removal occurred between 2 and 6 days after TURP [11,18], and early removal has been associated with an increased risk of post-TURP urinary retention [10]. With the increasing use of laser techniques such as GLPVP and HoLEP, catheter removal times have shortened to 1–4 days [3,4,9,19], and same-day catheter removal is feasible in selected patients, with reported success rates of 74%–90% [8,20,21]. Previous studies have reported wide variability in TWOC failure rates, ranging from 5.4% to 27.6% [7,22,23]. In our cohort, the mean TWOC timing was 2.4 days, reflecting a cautious but appropriate approach. Our initial TWOC failure rate of 12.5% aligns with these reports, and only 1% required long-term catheterization. Notably, only 3 patients developed long-term TWOC failure, all of whom had both DU (BCI: 36, 58, 75) and equivocal BOO (BOOI: 22, 37, 40) on urodynamic testing, despite having a wide range of preoperative PVR values (209–614 mL). These findings suggest that the combination of impaired detrusor contractility and minimal outlet resistance, rather than PVR alone, may better predict persistent postoperative bladder dysfunction and ongoing catheter dependence. Collectively, these results underscore the importance of early individualized risk stratification to guide catheter removal strategies.
Several factors have been proposed as predictors of initial TWOC failure after prostate deobstruction surgery, with large PVR and urinary retention being the most frequently cited [3,7,8,23]. These variables often reflect impaired detrusor contractility secondary to prolonged BOO, with associated bladder fibrosis delaying recovery [24]. Nonetheless, high PVR or retention does not consistently indicate detrusor decompensation, as some patients retain strong detrusor contractions but demonstrate poor voiding efficiency solely due to severe BOO. Our findings suggest that detrusor contractility, assessed through urodynamic parameters, is a more critical determinant of initial TWOC outcomes than PVR or retention alone.
Prostate volume has also been proposed as a predictor of initial TWOC failure, with larger volumes associated with catheter reinsertion in untreated retention cases [5,25]. Interestingly, some studies reported that smaller prostates were associated with TWOC failure after GLPVP and HoLEP [7,9], suggesting that prostate volume alone is unreliable. Although benign prostatic enlargement contributes to BOO, BOOI derived from pressure-flow studies correlates only weakly with prostate volume [26]. Theoretically, patients with higher BOOI values should experience greater symptomatic improvement after deobstruction surgery. Accordingly, our findings support BOOI as a more accurate and clinically relevant predictor of initial TWOC outcomes than prostate volume.
Age and DM have also been identified as predictors of TWOC failure in patients with BPO [11,12,25]. However, in our cohort, DM was not a significant factor, and age demonstrated only borderline significance in univariate analysis before losing significance in the multivariate model. Age-related changes may affect detrusor remodeling and contractility, which may explain why age lost significance after adjusting for DU.
The model of Fusco et al. suggests that chronic BOO elevates hydrodynamic pressure, leading to detrusor hypertrophy, collagen deposition, fibrosis, and ultimately DU [24]. DU is primarily diagnosed using invasive multichannel urodynamics [27], whereas non-invasive indicators such as low Qmax, prolonged flow, and elevated PVR are associated but lack definitive diagnostic cutoffs [28,29]. Patients with DU typically exhibit poorer voiding improvement after deobstruction, although 69%–78% may recover detrusor contractility over time [30-32]. Consequently, DU increases the likelihood of initial TWOC failure. Our previous work demonstrated that DU combined with low BOO (BOOI<20) significantly increases the risk of deobstruction surgery failure [33]. Zhu et al. [2] similarly reported that severe DU (BCI<82) accompanied by equivocal BOO (20 ≤ BOOI<40) predicted poorer outcomes. These findings collectively reinforce the importance of multichannel urodynamic studies as part of the preoperative evaluation for prostate deobstruction surgery.
Our study showed that DU and low BOO are independent predictors of initial TWOC failure after prostate deobstruction surgery. Patients with both DU and low BOO had an especially high failure risk (OR, 4.560; P=0.003), whereas those with preserved detrusor contractility and high BOO had a low risk (OR, 0.321; P=0.003), even within the subgroup of patients with elevated preoperative PVR. These results further support the utility of multichannel urodynamic evaluation for identifying high-PVR patients who are nonetheless suitable candidates for TWOC, thereby improving postoperative management strategies. For patients with DU and low BOO, TWOC may be postponed or closely monitored, whereas in those with high BOO and intact detrusor function, TWOC can be performed with confidence—even when preoperative PVR is high.
Despite the strengths of our findings, several limitations should be acknowledged. The retrospective study design introduces inherent risks of bias. Although selection bias is unavoidable in observational research, it was mitigated through consistent institutional protocols. Indication bias was minimized by prospective review of all deobstruction cases for urodynamic indications by 2 dedicated urologists, with shared decisionmaking when European Association of Urology guideline criteria were met. Operator variability could have influenced TWOC outcomes, although all operations were performed by experienced, board-certified urologists. Information bias was reduced through standardized urodynamic testing performed by trained technicians under close supervision, coupled with independent data extraction and partial cross-validation. Only 23 patients (7.0%) underwent HoLEP, limiting subgroup analysis, although sensitivity testing supported the robustness of the findings. Restriction of the cohort to patients who underwent preoperative multichannel urodynamics may limit generalizability; however, the results highlight the importance of these studies in evaluating high-PVR patients, as findings may influence initial TWOC decisions. For patients unable to undergo urodynamics, more conservative postoperative catheter management—particularly in those with high preoperative PVR—may be appropriate. We also advocate that institutions without existing urodynamic capacity consider expanding access for selected high-risk patients. Future prospective, multicenter investigations are warranted to validate these findings and to refine patient selection criteria for preoperative urodynamic evaluation.
In conclusion, prostate deobstruction surgery significantly improves uroflowmetry parameters in men with BPO. Approximately 12.5% of patients experience initial TWOC failure, although only 1% require long-term catheterization. Preoperative multichannel urodynamic studies provide valuable predictive insight into initial TWOC outcomes, with DU and low BOO emerging as independent risk factors. In clinical practice, these results support a more individualized postoperative catheter strategy based on objective assessments of bladder function rather than PVR alone. For patients with both DU and low BOO, postponing the initial TWOC is advisable, whereas for those with preserved detrusor contractility and high BOO, TWOC can be safely performed—even when preoperative PVR is elevated.
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