Pre and post void ultrasound are noninvasive bladder scans measuring urine volume before and after urination. Comparing these volumes yields the post void residual (PVR), indicating how completely the bladder empties. They help evaluate urinary retention, incontinence, recurrent infections, and lower urinary tract symptoms, guide treatment decisions, and monitor response without need for catheterization.

Worry when pre-void volumes are consistently very low (about ≤150–200 mL) or unusually high (about ≥400–500 mL), or when they’re paired with symptoms: urgency, frequency, weak stream, incomplete emptying or dribbling, pain, fever, blood in urine or recurrent UTIs. Also seek urgent care for inability to pass urine. A clinician can check bladder scans/post-void residuals and investigate underlying causes.

KUB (kidneys–ureters–bladder) is a plain abdominal X‑ray that shows bowel gas patterns, calcifications and radio‑opaque kidney or bladder stones and organ outlines. A post‑void residual image is taken after the patient urinates to assess how much urine remains in the bladder, helping detect urinary retention. The exam is quick and low‑dose but limited for soft‑tissue detail; ultrasound better quantifies residual volume.

A post‑void residual (PVR) is the volume of urine left in the bladder after urination. It’s measured by ultrasound or catheter; values under about 50 mL are generally normal, while persistent volumes above 100–200 mL suggest incomplete emptying. High PVR can indicate bladder outlet obstruction, weak bladder muscle, or neurological problems and raises risk of urinary infections, stones and, if chronic, kidney damage.

A KUB ultrasound (Kidneys, Ureters, Bladder) is a non-invasive imaging test using sound waves to evaluate the urinary tract. It assesses kidney size, cysts, hydronephrosis, bladder wall, urinary retention and may detect some stones or obstructions. It’s commonly used for flank pain, blood in urine or urinary symptoms. A full bladder is often required; small stones may need CT for confirmation.

Treatment for post-void residual urine depends on cause and severity: conservative measures (double voiding, timed voiding, pelvic-floor and bladder training), medications (alpha-blockers for outlet obstruction; antimuscarinics or beta-3 agonists for overactive bladder), clean intermittent self-catheterization for significant retention, antibiotics if infection is present, and procedures (e.g., TURP) or sacral neuromodulation for refractory cases. Monitor PVR.