Calculate post void residual (PVR) bladder volume from ultrasound measurements. Assess bladder emptying efficiency for urological evaluation.
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Post void residual (PVR) is the volume of urine remaining in the bladder immediately after urination. It is measured by bladder ultrasound (BUS) or catheterization. Elevated PVR indicates incomplete bladder emptying (urinary retention), which can lead to urinary tract infections, bladder damage, and kidney complications if untreated.
Formula: PVR (mL) = 0.523 × Length × Width × Height (all in cm)
A PVR below 50 mL is generally considered normal in most clinical guidelines. Some guidelines accept up to 100 mL in older adults as borderline acceptable, depending on symptoms and clinical context.
Common causes include benign prostatic hyperplasia (BPH) in men, neurogenic bladder (from diabetes, multiple sclerosis, or spinal injury), bladder outlet obstruction, urethral stricture, and medications such as anticholinergics or alpha-antagonists.
PVR is most commonly measured by portable bladder ultrasound (BladderScan) within minutes of voiding. Catheterization provides the most accurate measurement but is more invasive. Ultrasound is preferred for routine clinical use.
Voiding efficiency is the percentage of bladder volume expelled during urination: (Pre-void volume − PVR) ÷ Pre-void volume × 100. A voiding efficiency above 80% is generally considered adequate.
Yes. Common culprits include antihistamines, anticholinergics (oxybutynin, tolterodine), tricyclic antidepressants, opioids, and some antipsychotics. Always review medications when evaluating elevated PVR.
Consult a urologist if your PVR consistently exceeds 100 mL, especially if accompanied by urinary symptoms (hesitancy, weak stream, frequent UTIs, overflow incontinence, or nocturia). A PVR ≥ 300 mL may require catheterization.