Effects of diet and aging on renal measurements in uninephrectomized geriatric bitches

Under controlled, but varied dietary conditions among geriatric, uninephrec tomized Beagle bitches (dogs) observed for 4 years, renal size increase as assessed radiographically and ultrasonographically occurred at variable rat es, but on a seemingly continuous basis. The maximum observed mean renal li near parameter increase found was approximate to 15%. However, a 10 and 15% increase is a more representative expectation among the 4 parameters (sono graphic length, radiographic length, sonographic width, radiographic width) under consideration. The rate of renal size increase was rapid during the first 2 to 3 months following uninephrectomy. Thereafter, the rate of incre ase was slow, but occurred to varying degrees in both the length and width as assessed radiographically or ultrasonographically. The mechanism creatin g the size change was hypertrophy, not hyperplasia. Within limits of the 3 diets used in the study, no significant diet effect was found on the rate o r degree of long term compensatory hypertrophy. Radiographically and ultras onographically measured renal length had the greatest correlation with each other as well as with post mortem measurements and are, therefore, the rec ommended parameter for imaging assessment of compensatory hypertrophy. When the prenephrectomy, radiographic renal lengths and widths were normali zed as a ratio of the second lumbar vertebral body length (L-2) measured fr om ventrodorsal radiographs, the diet group means across dogs (approximatel y three L-2 lengths for renal length; two L-2 lengths for renal width) were in the middle of the respective previously published normal radiographic r anges for mature dogs (e.g. 2.5 L-2 less than or equal to length less than or equal to 3.5 L-2; 1.58 L-2 less than or equal to width less than or equa l to 2.38 L-2 lengths). Even after the hypertrophic changes occurred, the r adiographic group mean lengths and widths across dogs were still within the specified normal ranges, although toward the upper end of the respective r ange. This information provides background for clinical interpretation of p otential compensatory hypertrophy that may be encountered following unineph rectomy for spontaneous disease in aged dogs. In addition, it appears that available radiographic renal linear ranges for normal mature dogs are appli cable to geriatric dogs as well.