Urodynamic stress incontinence (USI) is distinguished from detrusor overactivity (DO) on multichannel cystometry by which finding?

• A USI: detrusor pressure rise >10 cmH₂O during cough; DO: no detrusor pressure change during provocation
• B USI: reduced bladder capacity <250 mL; DO: normal capacity with first sensation at >500 mL
• C USI: post-void residual >150 mL; DO: empty bladder on ultrasound post-void
• D USI: urine leakage coinciding with increased abdominal pressure (cough) without a rise in detrusor pressure; DO: phasic uninhibited detrusor contractions >6 cmH₂O during filling ✓

Explanation

On multichannel (subtracted) cystometry, detrusor pressure (Pdet) = bladder pressure (Pves) minus abdominal pressure (Pabd). Urodynamic stress incontinence (USI) is defined as leakage during increased abdominal pressure (cough, Valsalva) with NO corresponding rise in Pdet — confirming that the urethra cannot withstand the transmitted pressure increase without detrusor contraction. Detrusor overactivity (DO) is diagnosed when uninhibited phasic Pdet rises of any amplitude occur spontaneously or with provocation during filling, which may or may not cause leakage. The ICS/IUGA definition of DO requires a Pdet rise during the filling phase, typically >6 cmH₂O in clinical practice, occurring involuntarily.

Reference: Shaw's Textbook of Gynaecology, 17th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.