Calculate and interpret post-void residual urine volume, voiding efficiency, and flow rate as a lower-urinary-tract worksheet rather than a stand-alone treatment rule.
Post-void residual (PVR) volume is the amount of urine remaining in the bladder after a voluntary void. It is commonly reviewed in urology, gynecology, rehabilitation, and primary care when the question is whether the bladder is emptying efficiently or leaving behind a meaningful residual.
This calculator computes PVR from pre-void bladder volume and voided volume, or accepts a directly measured residual from catheterization or bladder ultrasound. It also shows voiding efficiency and a simple flow-rate estimate so the residual can be interpreted in the same context as the void itself.
The page is most useful as a worksheet for organizing bladder-scan or catheterization numbers. Symptoms, medication effects, infection, neurologic disease, and overall bladder function still determine what the next step should be.
PVR is useful because it turns symptoms like frequency, hesitancy, weak stream, or incomplete emptying into a number that can be trended. Pairing the residual with voiding efficiency and flow-rate context makes the result easier to review than a single isolated bladder-scan value.
PVR = Pre-Void Volume − Voided Volume (or direct measurement) Voiding Efficiency = (Voided Volume / Pre-Void Volume) × 100% Flow Rate = Voided Volume / Voiding Time (mL/s)
Result: PVR = 150 mL, voiding efficiency = 62.5%, flow rate = 8.3 mL/s
With 400 mL pre-void volume and 250 mL voided, the worksheet residual is 150 mL. Voiding efficiency is 62.5%, meaning a sizeable portion of the bladder volume remained after the void. The flow-rate estimate is 8.3 mL/s, which can be reviewed alongside symptoms and the actual measurement method.
PVR is strongest when it is interpreted with symptoms and the voiding situation that produced it. A mildly elevated residual in a comfortable outpatient setting does not mean the same thing as the same number in a patient with pain, neurologic disease, recurrent infections, or catheter problems.
Voiding efficiency expresses how much of the bladder volume was actually emptied. That makes it easier to compare a large-capacity bladder with a small-capacity one and to see whether the residual is a large share of the total or only a small leftover.
One PVR can be useful, but trends are often more informative. Repeated measurements under similar conditions can show whether the residual is stable, worsening, or improving after medication changes, surgery, or conservative management.
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This worksheet calculates a residual urine volume either by subtracting voided volume from the pre-void bladder volume or by accepting a directly measured post-void residual from bladder scan or catheterization. It also estimates voiding efficiency and a simple average flow-rate so the residual can be reviewed in the same context as the void itself.
The output is a lower-urinary-tract worksheet rather than a stand-alone treatment rule. Symptoms, measurement timing, infection, medications, neurologic disease, and the measurement method all influence what a given residual means.
Many references treat less than 50 mL as a low residual and more than 200 mL as clearly elevated, but the clinical meaning still depends on symptoms, measurement timing, and why the test was performed.
Catheterization is usually the direct reference method but is invasive. Bladder ultrasound is non-invasive and widely used for screening, serial checks, and bedside review, though accuracy varies with body habitus, operator technique, and abdominal conditions.
Anticholinergics, opioids, antihistamines, decongestants, tricyclic antidepressants, and some antipsychotics can all worsen emptying. Reviewing medication changes is often helpful when retention symptoms start abruptly.
No. Outlet obstruction is one possibility, but detrusor underactivity, neurogenic bladder, post-operative effects, pain, constipation, and medication effects can all produce a high residual.
The closer the measurement is to the void, the more faithfully it reflects the actual post-void residual. Delays allow ongoing urine production and can make the residual look higher than it really was at the end of voiding.