Sonographic evaluation of renal appearance in 665 adult volunteers. Correlation with age and obesity.

The purpose of this study was to investigate the sonographic appearance of the normal adult kidney. Parenchymal echogenicity, pyramid visibility, and transverse pelvis diameter of the kidneys were prospectively determined in an age- and sex-stratified random sample of 665 volunteers 30, 40, 50, 60, and 70 years old. Furthermore, incidences of kidney stones and split sinus echo were determined. The relation between obesity and above-mentioned parameters was evaluated. In the 30-year-old age group the right kidney was isoechoic as compared to the liver in 1/3, and had clearly or faintly visible pyramids in 2/3 of the cases. These rates decreased gradually with increasing age. Transverse diameter of renal pelvis > or = 10 mm was observed in 13% of participants. Renal stones were observed in 2.1%. The incidence of split sinus echo was 3.6%. Obese participants showed lower incidences of isoechogenicity, pyramid visibility, pelvic ectasia, and split sinus echo. Isoechoic parenchyma, clearly visible pyramids, and transverse pelvis diameter > or = 10 mm are not uncommon sonographic findings in normal adult kidneys and should not be used as indicators of renal pathology.