Validation of Ultrasonographic Kidney Volume Measurements: A Reliable Imaging Modality

Objectives: To investigate the kidney selection procedure before donation to maximize donor safety, we investigated whether ultrasonographic measurements of kidney volume are comparable with computed tomography measurements. Predonation volume and increases in kidney size may be important indicators of renal function after donation and subsequent loss of function. Materials and Methods: Consecutive donors with predonation computed tomography scans were approached preoperatively for additional ultrasono graphic examinations. Measurements were independently performed by 2 ultrasonographers and considered accurate when the mean differences between both examiners for length, width, and thickness of the kidneys were < 5 mm. Ultrasonographic volumes were calculated with the ellipsoid equation (length x width x thickness x pi/6) and an adjusted equation (length x width x thickness x 0.674), and computed tomography volumes were calculated with the voxel count method, which is considered the criterion standard. Results: For this study (Dutch Trial Register NTR3795), 100 kidneys were measured. The mean differences between examiner 1 and 2 for similar ultrasonography measurements were < 5 mm. The ellipsoid equation underestimated the volume for examiner 1 by 16.9% and for examiner 2 by 14.8%, whereas the adjusted equation overestimated the volume by 6.8% and 9.5% respectively. The correlation between computed tomography and ultrasonographic volume with the adjusted equation was strong for both examiner 1 (r = 0.76; P < .001) and examiner 2 (r = 0.80; P < .001). Conclusions: Ultrasonographic measurements of kidney volume are comparable with computed tomography measurements. Therefore, ultrasonography is a reliable modality for living kidney donor follow-up monitoring of kidney size adaption after donation.