prostate volume in mL assuming ellipsoid with 3 unequal axes =
= (maximal transverse diameter in cm) * (anteroposterior diameter of the prostate in cm) * (longitudinal diameter in midsagittal plane in cm) *
π / 6
where:
• The maximal transverse diameter is measured perpendicular to the anteroposterior plane.
• The anteroposterior diameter is taken in the transverse plane at a point perpendicular to the greatest transverse diameter.
• The longitudinal diameter through the midsagittal plane contains the urethra.
formula of Myschetzky et al for prostate volume in mL =
= (maximal transverse diameter in cm) * (anteroposterior plane of the prostate in cm) * (longitudinal diameter in midsagittal plane in cm) * π / 6 * 0.70
prostate volume in mL assuming prolate spheroid =
= ((maximal transverse diameter in cm)^2) * (longitudinal diameter in midsagittal plane in cm) * π / 6
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True Prostate Volume
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Estimate as Ellipsoid vs True Volume
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Impact on PSA Density Using Estimate
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< 30 mL
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formulas usually overestimate volume by +10 +/- 37% (+47 to –27%)
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density underestimated
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30 – 39 mL
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maximal accuracy for formula but underestimates by –8 +/- 12% (+4 to –20%)
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density overestimated
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40 - 49 mL
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formula underestimates volume by –28 +/- 15% (-13 to –43%)
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density overestimated
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>= 50 mL
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formula underestimates volume, with maximal imprecision by –33 +/- 27% (-6 to –63%)
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density overestimated
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NOTES: I wonder if the Myschetzky formula is better for small prostates, the ellipsoid for moderate sized ones and the prolate spheroid for large ones. Another approach might be to take the average of the Myzchetzky and ellipsoid formula for small prostates.
