Which urodynamic finding differentiates stress urinary incontinence from detrusor overactivity (urgency incontinence) on filling cystometry?

• A Involuntary detrusor contractions during filling phase in detrusor overactivity ✓
• B Maximum cystometric capacity reduced to <200 mL in detrusor overactivity
• C Post-void residual volume >100 mL in stress urinary incontinence
• D Reduced urethral closure pressure exclusively in detrusor overactivity

Explanation

Detrusor overactivity (urgency incontinence) is defined urodynamically by involuntary detrusor contractions (pressure rises >5 cm H2O) during the filling phase of cystometry, occurring either spontaneously or on provocation. Stress urinary incontinence shows leakage at increased abdominal pressure (coughing, straining) with no detrusor contractions; it is confirmed by demonstration of urethral hypermobility or reduced urethral closure pressure. Post-void residual is not a distinguishing criterion between these two.

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

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