Which component assesses bladder outlet function during urodynamics?

• A. Postvoid residual
• B. Cystometry
• C. Uroflowmetry
• D. Pressure-flow study

Answer: (D)

The key idea is that outlet function during voiding is best understood by how the bladder pressure relates to the flow of urine. This is captured with a pressure-flow study, where detrusor pressure is measured at the same time as the actual urine flow during voiding. The pattern helps distinguish obstruction from weak bladder contraction: high detrusor pressure with low flow points to bladder outlet obstruction (at the bladder neck or urethra); high pressure with good flow suggests the outlet is functioning well; low detrusor pressure with low flow points to detrusor underactivity rather than obstruction. Other tests have different roles—uroflowmetry records flow rate alone, cystometry focuses on storage and outlet behavior during filling and voiding but not the pressure-flow relationship, and postvoid residual indicates how much urine remains after voiding without assessing dynamic outflow.