Determination of renal volume by ultrasound scanning

In patients with renal hypertension, determination of renal volume may be valuable for evaluating possible compensatory hypertrophy for correlating renal size to renal function, and for evaluating the transplanted kidney in relation to rejection and its response to therapy. We performed parallel transverse ultrasonic scans through each kidney and computed volume based on the cross-sectional areas outlined on the scans. In 16 autopsy studies a highly significant correlation between calculated and true values were obtained, rs = 0.847, p less than 0.001. The 5th and 95th percentiles of the median divergence were -21 and 27 ml respectively. In 30 healthy subjects, double determinations showed 5th and 95th percentiles of the median interobserver variation of -7 and 3 ml respectively. There was no demonstrable difference between volumes of right and left kidneys, and no difference in relation to sex. Total renal volume was most accurate when correlated with the body weight, rs = 0.698, p less than 0.001. Normal values of total renal volume per kilogram of body weight were 4.3 to 8.0 ml/kg. In normal subjects, the smallest kidney's volume should not be less than 37% of the total renal volume.