THE COMPARATIVE ROLE OF HEMOGLOBINEMIA AND HYPOXIA IN THE DEVELOPMENTOF CANINE BABESIAL NEPHROPATHY

Renal pathology associated with haemoglobinaemia resulting from Babesi a canis infection is ascribed to haemoglobinuria, with or without a co ntribution from anaemic hypoxia. This study was undertaken to investig ate the relative roles of haemoglobinaemia and hypoxia in renal functi on and pathology in the dog. Three groups of 6 dogs each were used ove r a 4-day period. The dogs in the Ist group were infused with homologo us canine haemoglobin, anaemic hypoxia was induced in the 2nd group, a nd both treatments were applied in the 3rd group. Full urinalyses, ser um urea and creatinine concentrations, fractional clearance of sodium and the activity of urine enzymes, were assessed daily. At the end of the trial period, the glomerular filtration rate (GFR) was determined and kidney specimens collected for light and electron microscopy. In t he group with hypoxia only, the urine sediment contained more casts an d a greater number of renal tubular epithelial (RTE) cells than in eit her of the other groups. Hypoxia resulted in greater enzymuria, sugges tive of RTE cell pathology, whereas haemoglobinuria did not appear to have any effect on urine enzyme activity. Hypoxia resulted in a decrea sed GFR. Histological examination revealed a mild, single-cell tubular necrosis in the majority of the animals (all 3 groups), with granular casts in the hypoxic groups. There appeared to be a large individual variation in the ability of the kidney to handle infused haemoglobin. It was concluded that severe haemoglobinaemia did not induce a signifi cant nephropathy, anaemic hypoxia appeared to cause a very mild nephro pathy, and the combination of haemoglobinaemia and anaemic hypoxia did not exacerbate this change. These lesions were very different from th ose described in canine babesiosis.