The aim of this study is to evaluate postoperative outcomes in patients who underwent bladder outlet obstruction (BOO) surgery and met the European Association of Urology (EAU) guideline-based indications for preoperative invasive urodynamic studies (UDS).

After Institutional Board Approval, male patients who underwent BOO surgery between 2014 and 2025 following invasive UDS performed in accordance with International Continence Society (ICS) standards were included. Exclusion criteria comprised previous BOO surgery, pelvic radiotherapy or surgery, UDS recordings not compliant with ICS standards, or repeated urethral interventions due to postoperative hematuria or urethral stricture.
Preoperative assessment included suprapubic ultrasonography to evaluate prostate volume and the presence of a protruding median lobe which was defined as an intravesical prostatic extension exceeding 1 cm. 
UDS was performed using an Aymed device, adhering to ICS standards. 
In cases where voiding was not possible, the presence or absence of detrusor contraction during the attempt was documented.
Postoperative follow-up included measurement of post-void residual (PVR) urine volumes and assessment of patient status via standardized telephone interviews conducted by the same clinician. In these interviews, the voiding phase questions of the ICIQ M-LUTS questionnaire were directed, and patients were asked about the need for additional treatments related to voiding symptoms. 
Treatment success was defined as the absence of additional interventions (including pelvic floor muscle exercises or clean intermittent catheterization [CIC]) and a PVR volume of <150 mL at the most recent follow-up.

A total of 79 patients with a median age of 71 years (IQR: 16; range: 35–92) were included.  Median prostate volume and median follow-up duration were 50 mL (IQR: 40; range: 15–200), and 29 months (IQR: 27; range: 1–131), respectively. Nineteen patients (24%) had diabetes mellitus, and 12 patients (15.1%) had a documented neurological disease. Before surgery, 37 patients (46.8%) had an indwelling urethral catheter. Median lobe protrusion was identified in 28 patients (35.4%). Pressure flow study (PFS) could be performed in 14 of these patients (50%), all of whom demonstrated obstructive patterns. In patients with PFS, BOOI >40 was observed in 78.5% (11/14) of catheterized patients and 83.3% (25/30) of non-catheterized patients.
At the most recent follow-up, the overall treatment success rate was 93.6% (n = 74). Two patients continued CIC, two patients were managed with bladder training and pelvic floor muscle exercises, and one required indwelling urethral catheter.
Treatment success rates were stratified by preoperative UDS findings and catheter status (Tables 1 and 2). Among patients who underwent PFS, treatment success was 92.8% (13/14) in those with an indwelling catheter and 96.6% (29/30) in those without. Among patients with a median lobe, the treatment success rate was 96.4% (27/28). Notably, patients with a median lobe who could not undergo PFS but exhibited detrusor contraction during voiding attempts had a 100% (22/22) success rate.

Our findings suggest that treatment efficacy is highest where PFS confirmed obstruction. In contrast, for patients in whom PFS could not be performed due to failure to void upon permission, no reliable urodynamic parameter currently exists to predict BOO surgery success, underscoring the need for thorough preoperative counselling. Patients with a visible median lobe who demonstrated detrusor contraction during voiding attempts, despite the absence of a formal PFS, appeared to have better treatment outcomes.

BOO surgery is associated with favorable long-term outcomes in patients with obstructive findings on preoperative PFS. Pressure-flow studies remain the most informative tool, while in their absence, findings should be interpreted cautiously within the overall clinical context.