Bladder Scanning and Post-Void Residual Measurement

A post-void residual (PVR) is the volume of urine left in the bladder after a person has made a voluntary attempt to void. It answers one focused question: how completely did the bladder empty on this occasion? PVR is not a diagnosis. A high value may occur because urine cannot pass easily through the outlet, because the detrusor muscle does not contract effectively, or because pain, immobility, constipation, medication effects, or an unfamiliar setting interfered with normal voiding. The number becomes clinically useful only when it is paired with the person’s symptoms, voiding pattern, bladder capacity, underlying conditions, and risk of complications. Incomplete emptying can produce an apparently contradictory pattern. The person may void frequently, pass small amounts, and report urgency or leakage, yet still retain a substantial amount of urine. This is overflow incontinence: the bladder remains overfilled and leaks when pressure exceeds outlet resistance. It differs from overactive bladder, in which urgency is driven by involuntary detrusor activity and the bladder may empty reasonably well. A low PVR does not rule out urinary symptoms. A person with frequency,...