The correlation of post-pressure flow study and spontaneous post-voiding residual urine volume measurements with bladder contractility and bladder outflow obstruction indices in men with non-neurogenic luts

Abstract

Objective To compare post void residual (PVR) urine values measured after pressure flow studies (PFS) with spontaneous PVR measurements obtained at any time point. To evaluate these two PVR measurement approaches, obstruction and contractility indices obtained during PFS were utilized. Methods We retrospectively analyzed men with non‐neurogenic lower urinary tract symptoms undergoing PFS between 2018 and 2024. Patients were classified using both the Abrams–Griffiths (AG) nomogram and UPSTREAM derived thresholds. Subgroups stratified according to obstruction and contractility status were compared in terms of lower urinary tract parameters, particularly PVR values measured after spontaneous voiding and those measured after PFS. In addition, the ability of specific PVR threshold values to discriminate between obstruction and contractility states was analyzed using classifications based on nomograms. Results A total of 227 men were included (median age: 62 years). According to the AG classification, only post PFS PVR volumes were significantly higher in patients with detrusor underactivity (DU) ( p = 0.012). According to the AG classification, both spontaneous and post PFS PVR volumes were significantly higher in obstructive patients ( p = 0.001 and p = 0.036, respectively). Under the UPSTREAM classification, only spontaneous PVR remained significantly higher in the obstructive group ( p = 0.003). Post PFS PVR > 100 mL was significantly more frequent in underactive patients across both AG and UPSTREAM classifications and, according to AG, in obstructive patients. In addition, post PFS PVR > 200 mL was significantly associated with DU in the UPSTREAM classification. ROC analysis demonstrated that post PFS PVR predicted DU with an AUC of 0.599 (95% CI: 0.522–0.677, p = 0.013); a 67.5 mL threshold yielded 58% sensitivity and 58.3% specificity. Conclusion Post PFS PVR correlates more with DU, while spontaneous PVR is more associated with bladder outlet obstruction. Higher post PFS PVR values (> 200 mL) suggest impaired detrusor contractility. Measurement approaches and thresholds may help differentiate underlying pathology.