Hypothesis / aims of study
Videourodynamic study (VUDS) is the standard diagnostic approach for young men with lower urinary tract symptoms (LUTS), yet existing VUDS studies report only the post-VUDS diagnostic spectrum without quantifying the directional shift from pre-VUDS clinical diagnosis [1,2]. A systematic review of five VUDS studies reported primary bladder neck obstruction (PBNO) as the dominant diagnosis (49%) with detrusor underactivity (DU) at only 3%, but noted that pre-VUDS clinical diagnoses were reported in only 3 of 10 included studies [3]. This study aimed to construct a diagnostic migration matrix mapping exactly which clinical diagnoses are most unreliable and where their patients redistribute after VUDS in young males with LUTS.
Study design, materials and methods
Males aged <40 years presenting with LUTS of ≥3 months duration at a tertiary care centre underwent clinical evaluation in this prospective observational study , International Prostate Symptom Score (IPSS), uroflowmetry with post-void residual measurement, and multichannel VUDS per International Continence Society good urodynamic practices [4]. Patients with neurological disease, prior lower urinary tract surgery, urethral trauma or stricture, urinary tract infection, or benign prostatic enlargement were excluded. Each patient received a pre-VUDS clinical diagnosis — bladder outlet obstruction (BOO), underactive bladder (UAB), or overactive bladder (OAB). Post-VUDS diagnoses were classified as PBNO, dysfunctional voiding (DV), DU, or detrusor overactivity (DO) using fluoroscopic and pressure-flow criteria. A diagnostic migration matrix was constructed cross-tabulating every pre-VUDS category against its post-VUDS destination.
Results
180 young males (mean age 27.6 ± 6.75 years, mean IPSS 18.3 ± 5.5) underwent VUDS. Abnormal findings were present in 169 (93.9%). Post-VUDS diagnoses: DU 59 (32.8%), PBNO 57 (31.7%), DV 41 (22.8%), DO 12 (6.7%), normal 11 (6.1%). DU prevalence was substantially higher than the 3% pooled VUDS estimate in the only available systematic review [3].
Diagnostic migration matrix:
Pre-VUDS → PBNO → DV → DU → DO → Normal
BOO (n=106) 45 (42.4%) 31 (29.2%) 21 (19.8%) 0 9 (8.5%)
UAB (n=54) 10 (18.5%) 6 (11.1%) 36 (66.7%) 0 2 (3.7%)
OAB (n=20) 2 (10.0%) 4 (20.0%) 2 (10.0%) 12 (60.0%) 0
Clinical suspicion of BOO had the lowest confirmation rate (42.4%), with 49.0% of clinically suspected obstruction proving non-obstructive — predominantly DV (29.2%) and DU (19.8%). UAB showed 66.7% and OAB 60% concordance. DV was the only diagnosis concealed within all three clinical categories (31 from BOO, 6 from UAB, 4 from OAB), identifiable only through the fluoroscopic component of VUDS. PdetQmax was highest in PBNO (57.4 ± 25.3 cmH₂O) and lowest in DU (13.5 ± 14.9 cmH₂O); residual volume differed nearly 9-fold between DU (257 ± 156 ml) and DO (29.5 ± 40.2 ml).
Interpretation of results
This diagnostic migration matrix — the first using VUDS in young males — reveals that clinical BOO, the diagnosis most commonly triggering empirical alpha-blocker therapy, is the least reliable clinical category. DU prevalence (32.8%) was 10-fold higher than the pooled VUDS estimate [3], suggesting prior underdiagnosis. DV masquerades across all clinical categories and requires fluoroscopic visualisation unique to VUDS for identification.