A simple method to estimate renal volume from computed tomography

Abstract

Introduction: 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%. Conclusion: 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.

Association of mGFR of the Remaining Kidney Divided by Its Volume before Donation with Functional Gain in mGFR among Living Kidney Donors

“…a For example, the adjusted 5-year functional gain regarding age at donation in model 1 is 20.3, meaning that, for an additional 1 year of age, the 5-year functional gain will be reduced by 0. The adjusted volume of the kidney estimated using the ellipsoid equation (19) was highly correlated with the adjusted kidney volume measured using renal CT scan (R=0.82; P,0.001). We tested our model using the rk-GFR/vol computed with the volume estimated with the ellipsoid equation and found that rk-GFR/vol is still statistically significant at the 5% level and that the predictive power of the model is as high as the model that included kidney volume measured using renal CT scan (R 2 =0.41 with estimated volume).…”

“…The workup before donation included urinary albumin-to-creatinine ratio (ACR) on the second morning urinary spot measurement, 24-hour ambulatory BP measurement (ABPM) to depict hypertension according to the current guidelines (18), 51 Cr-EDTA GFR measurement, and SRF using renal scintigraphy (12). For 52 of the donors, the initial volume of the remaining kidney was measured using CT scan and also estimated with the ellipsoid equation (19) using only the measurements of the length, the lateral diameter, and the anterior-posterior diameter of the kidney on CT scan. Renal scintigraphy and methods to measure GFR and kidney volume are described in Supplemental Table 1.…”

Estimating renal volume from CT: Is this the easiest way?

“…1 The authors found that the ellipsoid method underestimated 3D volume (170 cm 3 vs. 186 cm 3 , respectively), but that almost all were accurate 30%; they also concluded that measuring renal volume is easy and reliable. They also suggested that 3D volume software is not needed for the estimation of differential renal function.…”

“…http://dx.doi.org/10.5489/cuaj.1336 W e congratulate Breau and colleagues for demonstrating that there was good correlation between renal volume as measured by two techniques: the ellipsoid method and 3D volume measurement using specialized volumetric software with contrast-enhanced CT scans. 1 The authors found that the ellipsoid method underestimated 3D volume (170 cm 3 vs. 186 cm 3 , respectively), but that almost all were accurate 30%; they also concluded that measuring renal volume is easy and reliable. They also suggested that 3D volume software is not needed for the estimation of differential renal function.…”

“…In addition, the correlation between two estimated renal volume and DTPA kidney scintigraphy was not shown in this study by Breau and colleagues. 1 The question thus remains as to which result is more correlated with renal function.…”