Simplified method to measure renal volume: the best correction factor for the ellipsoid formula volume calculation in pretransplant computed tomographic live donor.

OBJECTIVE

To find an optimal correction factor that will produce a near-real renal volume calculation using the ellipsoid formula.

METHODS

We retrospectively studied 79 multidetector computed tomography (MDCT) examinations for potential renal donor assessment. The renal volumes were calculated using the slice summation method, the ellipsoid formula with π/6 as correction factors as well multiple other correction factors for statistical analysis. A paired Student t test was used for evaluating the volumes calculated with different correction factors and the volumes calculated by the slice summation method.

RESULTS

The ellipsoid formula using correction factor 0.524 underestimates the renal volume by approximately 22.2% with statistical difference compared with the slice summation method (P<.05). There is no statistical difference when using correction factor in the range of 0.664 to 0.686 (P>.05). Further subgroup analysis of gender and laterality was performed and revealed no statistical difference. Using a mean value of 0.674 or 0.67 as correction factor results in renal volumes that are 100% and 99.5%.

CONCLUSION

To avoid underestimation of the renal volume by the ellipsoid method, acceptable correction factors are in the range of 0.664 to 0.686. We suggest the use of a mean value of 0.674 or 0.67 as correction factor when using the ellipsoid formula.