Finding the right tests…
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Finding the right tests…
Sonography
PRE VIOD & PVRU measures how much urine sits in your bladder both before and after you urinate, comparing the two readings rather than checking bladder structure the way other scans in this list do. The pre-void scan captures your bladder volume while it's still full, and the post-void residual, or PVR, reading is taken right after you empty it, ideally within a few minutes, since the number changes quickly once new urine starts collecting again. A healthy adult usually empties down to less than 100 milliliters left behind, while a reading over 400 milliliters points toward significant urinary retention. This test is entirely mechanism-driven, a before-and-after comparison, rather than a single-moment structural picture.
This scan measures your bladder volume before you urinate and again right after, comparing the two to see how completely your bladder empties. A high post-void residual reading points toward urinary retention, while a low one suggests your bladder is emptying normally.
Most bladder scans capture a single moment, but PRE VIOD & PVRU is built around comparing two moments, before and after you urinate, to answer a specific question: is your bladder emptying the way it should.
The pre-void scan is taken while your bladder is still full, giving a starting volume. You then urinate as you normally would, and the post-void residual, or PVR, scan follows right after, measuring whatever urine is left behind. Timing matters here, since a delay of even a few minutes after voiding can make the leftover volume look artificially higher as new urine starts to collect.
Less than 100 milliliters left behind is generally considered normal for an adult, while more than 400 milliliters points toward significant urinary retention that needs further evaluation. Readings in between are interpreted alongside your symptoms rather than as a fixed cutoff.
An enlarged prostate, a neurological condition affecting bladder control, or bladder-emptying symptoms after surgery are common reasons your doctor wants this specific before-and-after comparison rather than a single bladder scan.
The pre-void scan measures your bladder volume while it's still full. The post-void residual scan is taken right after you urinate, measuring whatever urine is left behind.
New urine starts collecting again as soon as you finish urinating, so even a short delay before the post-void scan can make the leftover volume look higher than it really is.
Less than 100 milliliters left behind is generally considered normal for an adult, while more than 400 milliliters points toward significant urinary retention.
A regular bladder scan captures one moment. This test is specifically built to compare before and after urination, which a single-moment scan can't show.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
Yes, checking how completely the bladder empties is a common part of evaluating an enlarged prostate and similar bladder-emptying problems.
No, it's painless. It uses the same probe-and-gel technique as a standard bladder ultrasound, done twice around your normal urination.
No. It's ultrasound-based, using sound waves rather than X-rays, so there's no radiation exposure.
There's no single preparation that applies to everyone, though you'll need to be able to urinate during the visit for the second reading. Ask your doctor or the centre what to expect.