A cystometrogram assesses bladder pressure and volume during filling and voiding to evaluate detrusor function. Which pattern would suggest detrusor overactivity?

• A. It measures bladder pressure during filling only, without volume data.
• B. A sudden rise in intravesical pressure with minimal increase in volume during filling suggests detrusor overactivity.
• C. It measures urethral sphincter function during coughing.
• D. It records urinary frequency over 24 hours.

Answer: (B)

Cystometrogram tracks how the bladder pressure changes as it fills, so you can see how the detrusor muscle behaves during filling. Detrusor overactivity shows up as involuntary detrusor contractions while the bladder is filling. The characteristic pattern is a sudden rise in intravesical pressure with only a minimal increase in bladder volume, meaning the bladder contracts spuriously even though it hasn’t filled much yet. This pressure spike during filling is the telltale sign of overactive detrusor activity.

Other options don’t show this pattern: measuring pressure without concurrent volume data doesn’t reveal the pressure–volume changes of contractions; assessing urethral sphincter function during coughing relates to stress incontinence rather than detrusor behavior; and recording urinary frequency over 24 hours is a diary approach, not a filling cystometry finding.