How can urodynamics differentiate detrusor overactivity from intrinsic sphincter deficiency?

• A. Detrusor overactivity shows involuntary detrusor contractions during filling; intrinsic sphincter deficiency shows inadequate urethral closure with normal detrusor activity.
• B. Detrusor overactivity has decreased detrusor contractions; ISD shows high detrusor pressure.
• C. ISD shows absent bladder pressure changes; DO shows normal contractions.
• D. There is no difference on urodynamics.

Answer: (A)

Urodynamics distinguishes leakage sources by watching what the bladder muscle (detrusor) does during filling. In detrusor overactivity, the detrusor contracts involuntarily while the bladder is being filled, causing pressure spikes and leakage that are linked to these unintended contractions. In intrinsic sphincter deficiency, the detrusor behaves normally during filling—no involuntary contractions—yet leakage occurs because the urethral sphincter fails to close adequately. So, the key to differentiating them is the presence of involuntary detrusor contractions during filling versus normal detrusor activity with poor urethral closure.