Quantification of Renal Volume and length in Normal Subjects by Magnetic Resonance Imaging
Cheong B, Muthupillai R, Flamm S
St. Luke's Episcopal Hospital
In routine clinical practice, kidney length and kidney volume are measured by ultrasonography (US) using a formula that approximates the bean shaped kidney to an ellipsoid. The purpose of this study is to evaluate the accuracy of such an approximation. In an ex-vivo model of a porcine kidney, the ellipsoid formula underestimated the kidney volume by 21%, whereas the magnetic resonance imaging (MRI) method to compute volume using disc summation was within 5% of the volume obtained by the water displacement method. In 20 patients with no intrinsic kidney disease, using the ellipsoid formula to compute the volume resulted in an underestimation of 17-20% compared to the volume estimated from MRI data using the disc summation method. The mean kidney length and volumes estimated using MRI in 130 patients with no intrinsic kidney disease are greater than the hitherto reported reference values obtained using US.