Study of association between histologic features and echogenicity of architecturally normal cat kidneys.

Thirty-eight grossly and histologically normal cat kidneys were examined ultrasonographically. The echogenicity of the renal cortex was subjectively evaluated by scoring it as largely or not largely different from the echogenicity of the renal medulla and as similar or not similar to the echogenicity of the renal sinus. The presence or absence of a medullary hyperechoic band was determined. The length, width, and height of each kidney was measured. Hematoxylin and eosin-stained sections of each kidney were examined microscopically. The amount of fat vacuoles in the tubular epithelium of the renal cortex was scored as plentiful or not plentiful. The presence or absence of a medullary band of mineral deposits within the lumina of renal tubules was determined. A plentiful amount of fat vacuoles in renal cortex was associated positively with a large difference in echogenicity between cortex and medulla (P less than 0.01) and with similar echogenicity of cortex and sinus (P less than 0.01). The presence of a medullary hyperechoic band was associated positively with a band of mineral deposits within medullary tubular lumen (P 0.01). Kidneys with a large difference in echogenicity between cortex and medulla and kidneys with a plentiful amount of fat vacuoles were not significantly different in size (P = 0.56). These groups were larger (P less than 0.01) in length, width, and height than were kidneys without a large difference in echogenicity between cortex and medulla and kidneys that did not have plentiful cortical fat vacuoles.