title: A simple method to estimate renal volume from computed tomography.
abstract: BACKGROUND
  Renal parenchymal volume can be used clinically to estimate differential renal function. Unfortunately, conventional methods to determine renal volume from computed tomography (CT) are time-consuming or difficult due to software limitations. We evaluated the accuracy of simple renal measurements to estimate renal volume as compared with estimates made using specialized CT volumetric software.
  
  
  METHODS
  We reviewed 28 patients with contrast-enhanced abdominal CT. Using a standardized technique, one urologist and one urology resident independently measured renal length, lateral diameter and anterior-posterior diameter. Using the ellipsoid method, the products of the linear measurements were compared to 3D volume measurements made by a radiologist using specialized volumetric software.
  
  
  RESULTS
  LINEAR KIDNEY MEASUREMENTS WERE HIGHLY CONSISTENT BETWEEN THE UROLOGIST AND THE UROLOGY RESIDENT (INTRACLASS CORRELATION COEFFICIENTS: 0.97 for length, 0.96 for lateral diameter, and 0.90 for anterior-posterior diameter). Average renal volume was 170 (SD: 36) cm(3) using the ellipsoid method compared with 186 (SD 37) cm(3) using volumetric software, for a mean absolute bias of -15.2 (SD 15.0) cm(3) and a relative volume bias of -8.2% (p < 0.001). Thirty-one of 56 (55.3%) estimated volumes were within 10% of the 3D measured volume and 54 of 56 (96.4%) were within 30%.
  
  
  CONCLUSIONS
  Renal volume can be easily approximated from contrast-enhanced CT scans using the ellipsoid method. These findings may obviate the need for 3D volumetric software analysis in certain cases. Prospective validation is warranted.
authors.affiliation: Ottawa Hospital Research Institute, Ottawa, ON; ; Division of Urology, University of Ottawa, Ottawa ON;
authors.forename: Rodney H
authors.initials: RH
authors.lastname: Breau
authors.forename: Edward
authors.initials: E
authors.lastname: Clark
authors.forename: Bryan
authors.initials: B
authors.lastname: Bruner
authors.forename: Patrick
authors.initials: P
authors.lastname: Cervini
authors.forename: Thomas
authors.initials: T
authors.lastname: Atwell
authors.forename: Greg
authors.initials: G
authors.lastname: Knoll
authors.forename: Bradley C
authors.initials: BC
authors.lastname: Leibovich