Post-void residual
Formal Definition
The volume of urine remaining in the bladder after voluntary voiding, measured by bladder ultrasound (bladder scan) or catheterization; a key diagnostic measure in urinary retention, neurogenic bladder, and lower urinary tract dysfunction; normal is <50mL, significant retention is >200–300mL.
How It's Used on the Ward
"PVR" or "bladder scan" or "check a residual" — the quick ultrasound measurement to see how much urine is stuck in the bladder after voiding.
Example
""Patient complaining of urinary frequency and incomplete emptying: bladder scan shows post-void residual of 350mL. This is significant urinary retention. Starting tamsulosin, repeat bladder scan in 48 hours; if PVR remains elevated, urology referral.""
Clinical Context
Bladder scanner: portable ultrasound device that calculates bladder volume without catheterization. Quick, non-invasive, available at bedside. Interpretation: <50mL = normal; 50–199mL = equivocal (recheck); ≥200mL = clinically significant. Causes of elevated PVR: BPH (most common in older men), neurogenic bladder (diabetes, MS, Parkinson, spinal cord injury), post-anesthesia urinary retention (POUR), anticholinergic medications (common culprit — check the med list). POUR: common after spinal/epidural anesthesia — most resolve with one or two straight caths. Clean intermittent catheterization (CIC) for chronic high PVR to prevent overflow incontinence and protect kidneys.
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