Age and diet effects on relative renal echogenicity in geriatric bitches

Under controlled, but varied dietary conditions 35 geriatric, uninephrectom ized, spayed]Beagle bitches (dogs) observed for 4 years, renal cortical and renal medullary echogenicity was measured relative to hepatic and splenic echogenicity. Regardless of the diet fed, 60-75% of these aged dogs had ren al cortical echogenicity less than that of either the liver or spleen acros s time; 25-35% of these dogs had renal cortical echogenicity equal to that of the liver, but less than that of the spleen across time. Less than 3% of these dogs had renal cortical echogenicity greater than that of the liver, but less than that of the spleen. Only 1 tone) of these dogs had renal cor tical echogenicity equal to that of the spleen and that occurred at only on e of the 14 chronologic assessments. Therefore, in either mature or aged do gs imaged with 4.0 to 5.0 MHz equipment, the renal cortical echogenicity sh ould be considered normal if it is less than or equal to that of the liver and less than that of the spleen. In 29 dogs imaged with the 4.0/5.0 MHz eq uipment and 6 dogs imaged with 7.5 MHz equipment, there was no significant diet or individual dog effect. The 7.5 MHz (6 dog) group had significantly higher average cortical echogenicity scores than the 4.0/5.0 MHz (29 dog) g roup, However, the occurrence of renal cortical echogenicity greater than l iver echogenicity was seen in only 5 of 83 samples (approximate to 6,0%) ma de on 6 dogs imaged with 7.5 MHz equipment and only 1 of 375 samples approx imate to 0.27%) made on 29 dogs with 4.0/5.0 MHz equipment. With the except ion of one occurrence, all dogs had renal medullary echogenicity less than that of the liver or spleen regardless of imaging equipment frequency. The renal medulla was always hypoechoic compared to the cortex.