1. What is a Bladder Volume Calculator?

Definition: This calculator estimates bladder volume using ultrasound measurements based on the ellipsoid formula (MDCalc method).

Purpose: It helps medical professionals assess bladder volume non-invasively for urological evaluations and post-void residual measurements.

2. How Does the Calculator Work?

The calculator uses the ellipsoid formula:

Where:

• \( V \) — Bladder volume (cm³)
• \( L \) — Length (cm)
• \( W \) — Width (cm)
• \( H \) — Height (cm)

Explanation: The formula approximates the bladder as an ellipsoid shape, which is the standard method for ultrasound bladder volume estimation.

3. Importance of Bladder Volume Measurement

Details: Accurate bladder volume assessment is crucial for diagnosing urinary retention, monitoring bladder function, and evaluating post-void residuals.

4. Using the Calculator

Tips: Enter the three orthogonal measurements (length, width, height) in centimeters obtained from bladder ultrasound. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: How accurate is this calculation?
A: The ellipsoid formula has about 85-90% accuracy compared to actual bladder volume, with slight underestimation in very full bladders.

Q2: What's a normal post-void residual volume?
A: Typically <50 mL is normal, 50-100 mL is borderline, and >100 mL suggests significant retention.

Q3: Can I use this for pediatric patients?
A: Yes, but normal volumes vary significantly by age and body size in children.

Q4: How do I convert cm³ to mL?
A: They are equivalent (1 cm³ = 1 mL) for clinical purposes.

Q5: What if my ultrasound machine has built-in calculations?
A: This provides the same calculation method, useful when manual measurement is needed or to verify machine calculations.