Your estimated bladder volume is calculated using the prolate ellipsoid formula, which multiplies the three orthogonal ultrasound dimensions (width, height, and depth) by a correction factor of 0.52. A volume under 50 mL typically represents a near-empty bladder. Volumes between 200 and 400 mL are within the normal pre-void range for most adults. A volume exceeding 500-600 mL may indicate bladder over-distension, which can be seen in urinary retention, neurogenic bladder, or bladder outlet obstruction.

When used to assess post-void residual (PVR), a volume under 50 mL is considered normal, 50-100 mL is borderline, 100-200 mL is mildly elevated, and volumes above 200 mL are clinically significant and often warrant further workup. Persistently elevated PVR volumes may indicate incomplete bladder emptying due to obstruction (e.g., BPH) or detrusor underactivity.

Use this calculator whenever bedside bladder volume estimation is needed from ultrasound measurements. Common clinical scenarios include assessing urinary retention in postoperative patients, evaluating post-void residual volume in men with lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia, and monitoring bladder volumes in patients with neurogenic bladder or spinal cord injuries.

It is also useful in the emergency department for patients presenting with acute urinary retention, in the ICU for patients with indwelling catheters where catheter function is questioned, and in outpatient urology clinics as a complement to formal urodynamic studies.

The ellipsoid formula assumes a regular, spherical-to-oval bladder shape. In patients with significant bladder wall thickening, diverticula, or pelvic masses compressing the bladder, the estimation accuracy decreases substantially. The error margin for manual 2D ultrasound measurement is typically 15-25%, which is greater than automated 3D bladder scanners.

Operator technique significantly affects accuracy. Obtaining true orthogonal planes and correct caliper placement requires training. Additionally, this formula does not account for bladder wall thickness or intravesical masses (e.g., tumors, blood clots). For clinical decisions that depend on precise volume measurement, such as urodynamic studies or surgical planning, formal catheterized volume measurement remains the gold standard.