Background: As a result of the increasing popularity of Greyhounds as pets, veterinarians are likely to evaluate them more frequently in practice. Clinical experience has identified an increased frequency of certain disease syndromes, including renal disease, more specifically protein losing nephropathy and hypertension. Greyhounds are considered a model for primary hypertension in people. In human medicine, identifying early makers of renal disease such as microalbuminuria and hypertension, and subsequent control, is associated with a decreased rate of progression and increased survival.
Objectives: The objective of this study was to evaluate renal function and hemodynamic status in a population of clinically healthy retired racing Greyhounds (RRG’s). Our goals were to evaluate this group of dogs with respect to blood pressure, but also for any indication of early renal disease based on markers of renal damage including microalbuminuria, overt proteinuria, altered fractional excretion of electrolytes, and structural changes based on histopathology.
Animals: Forty-eight clinically healthy RRG’s that were presented in 2007 and 2008 for participation in a 3rd year student castration and ovariohysterectomy lab.
Methods: Immediately upon presentation, all dogs underwent a complete physical examination, urinalysis and urine profile, urine protein-creatinine ratio, urine culture, HESKA ERD microalbuminuria, blood pressure via Doppler ultrasonographic and oscillometric method, and pulse rate via digital palpation and the oscillometric monitor. On day 3 of hospitalization, all blood pressure and heart rate testing was repeated using identical methods. Twenty of the female dogs that underwent an exploratory laparotomy for ovariohysterectomy also had renal biopsies performed. Renal tissue was evaluated with light microscopy, immunofluorescence, and electron microscopy.
Results: Forty-seven dogs were enrolled in this study. Twenty-six were considered hypertensive (BP > 165mmHg) and 21 normotensive (BP < 165mmHg). There was a statistically significant difference between the systolic BP in these 2 groups. There was good correlation between the Doppler and oscillometric methods on the same day, and between each method on different days. There were no statistically significant differences between the 2 methods on the same day, or between each method on different days. Twenty-two of the dogs were negative for microalbuminuria and twenty-five were positive. There was a statistically significant association between the presence of hypertension and the presence of microalbuminuria, p< 0.001. There were no significant associations between hypertension and UPC, fractional excretion of electrolytes, or renal histopathology. There were no significant associations between the presence of microalbuminuria and fractional excretion of electrolytes or renal histopathology. Overall histopathologic changes were mild and nonspecific.
Conclusions and Clinical Relevance: There was a high incidence of hypertension in these Greyhounds, and the Doppler and oscillometric methods are both
appropriate for assessing blood pressure status in this breed. Stress did not appear to artificially raise the BP in these dogs as heart rate was generally low and there was no difference between heart rate in the normotensive and hypertensive Greyhounds. Additionally, no change in blood pressure was identified after a 48 hr acclimation period. There was also a fairly high incidence of microalbuminuria in these Greyhounds, and a significant association between the presence of hypertension and microalbuminuria. This may indicate a very early sign of renal dysfunction, and may be secondary to uncontrolled primary hypertension. Further study is warranted to evaluate whether the presence of microalbuminuria is associated with an increased risk of progression to overt proteinuria or chronic kidney disease, and whether blood pressure control impacts this progression.