Gynaecologic Imaging
Live dataOvarian Volume (Ellipsoid)
Calculates ovarian volume from three ultrasound diameters using the prolate-ellipsoid formula to distinguish a normal ovary from an enlarged or postmenopausal ovary.
The ovary approximates a prolate ellipsoid, so its volume is the product of the three orthogonal diameters and 0.523 (≈ π/6). Ovarian volume normally declines after the menopause; a value above the age-appropriate threshold, or marked asymmetry between the two ovaries, raises concern for a mass or functional process.
📐 Formula
Volume (cm³) = 0.523 × length × width × height
🎯 When to Use
- Characterising a suspected ovarian enlargement or mass.
- Assessing a postmenopausal ovary, where any measurable volume increase is more concerning.
- Follow-up of functional cysts and baseline for polycystic ovary assessment.
⚙️ How It Works
- Measure the ovary in three orthogonal planes (length, width, anteroposterior height) in cm.
- Compute volume = 0.523 × length × width × height.
- Compare against the menopausal-status threshold and against the contralateral ovary.
📊 Interpreting the Result
- Premenopausal upper limit of normal ≈ 10 cm³ (mean ~5–6 cm³).
- Postmenopausal upper limit ≈ 8 cm³; some references use ≤6 cm³, with a >2× volume difference between ovaries considered abnormal.
- A polycystic-appearing ovary is typically ≥10 cm³ with ≥20 antral follicles (2017 international PCOS criteria).
⚠️ Limitations & Pitfalls
- The ellipsoid model underestimates volume for irregular or multiloculated masses; measure the mass separately.
- Follicular and functional changes cause physiological volume variation across the menstrual cycle.
- Transabdominal measurement is less accurate than transvaginal, especially in obese patients.
📚 References
- Cohen HL, Tice HM, Mandel FS. Ovarian volumes measured by US: bigger than we think. Radiology. 1990;177(1):189-192.
- Pavlik EJ, DePriest PD, Gallion HH, et al. Ovarian volume related to age. Gynecol Oncol. 2000;77(3):410-412.
⚕️ For clinical decision support only. Always verify calculations and apply clinical judgment.