Objective: The purpose of this study was to investigate the normal sonographic measurements of the kidney in adult volunteers.
Subjects and methods: Length, width, and thickness of the kidney and its central echogenic area and the parenchymal thickness of the upper pole were measured in an age- and sex-stratified random sample of 665 volunteers 30, 40, 50, 60, and 70 years old. Measurements were made with the volunteers prone. Volumes of the kidney, the central echogenic area, and the renal parenchyma were calculated. Renal dimensions and renal and parenchymal volume were correlated with age, height, weight, body mass index, and total body area. In 94 subjects, renal length was measured with the volunteers supine also.
Results: Median renal lengths were 11.2 cm on the left side and 10.9 cm on the right side. Median renal volumes were 146 cm3 in the left kidney and 134 cm3 in the right kidney. Renal size decreased with age, almost entirely because of parenchymal reduction. Renal volume correlated best with total body area. Renal length correlated best with body height. Measurements of renal length obtained with the subjects supine were not significantly different from those obtained with the subjects prone.
Conclusion: The most exact measurement of renal size is renal volume, which showed the strongest correlation with height, weight, and total body area. Clinically, measurement of renal length is most practical and can be done with the subject prone or supine.