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The aim of this study was to evaluate clinical, laboratory, imaging and pathological findings of pet rabbits with azotemia (plasma creatinine concentration > 166 μmol/l) and to differentiate prerenal, renal [acute renal failure (ARF) and chronic renal failure (CRF)] and post renal azotemia using several criteria. In addition, the course and causes of azotemia were evaluated and compared between azotemia groups.
In a period of 13 years (2000 to 2013), data from 161 pet rabbits (50 animals prospectively, 111 retrospectively) were evaluated and the animals were divided into three azotemia groups. Rabbits with renal azotemia were the largest group (83/161), followed by animals with prerenal (30/161) and post renal (10/161) azotemia. Nearly a quarter of the rabbits (38/161) could not be reliably assigned to one of the azotemia groups through inconsistent findings. Within the renal azotemia group the majority of rabbits suffered CRF (56/83), ARF was less common (27/83). In all the azotemia groups mainly middle-aged rabbits were affected (median: 4 years). The animals of the CRF group were significantly older than the rabbits of the ARF group (median: 5.5 years; p = 0.013). The reasons of clinical presentation or the symptoms of rabbits with azotemia were mostly nonespecific. Anorexia occured most frequently (44 %, 70/161), followed by apathy (24 %, 39/161) and neurological symptoms (15 %, 24/161). Typical clinical signs of renal azotemia in dogs and cats like weight loss (14/161) and polyuria/polydipsia (4/161), however, were rarely observed. In most rabbits, clinical examination revealed a light (58/161) to moderately (47/161) reduced general condition, 27 % (43/161) of the rabbits were presented with hypothermia. Blood pressure was reduced in 57 % (12/21) of the animals. Creatinine concentrations of rabbits with ARF were significantly higher than in animals with prerenal and post renal azotemia. Despite increased creatinine concentrations (179-505 μmol/l) the urea concentration was found tob e within the reference range in 10 % (15/154) of the rabbits. In 17 animals with a slight elevation of the creatinine concentration (< 268 μmol/l) a high concentration of urea was found (17- 45 mmol/l). Hyperphosphatemia and hypocalcemia (total and ionized calcium) were most frequently observed (75/122, 42/123,20/56). In addition, hyperkalemia (48/118) and hyponatremia (44/108) were found in rabbits with renal azotemia. Total protein concentration and albumin concentration were reduced in 28 % (36/127) and 70 % (66/95) of the rabbits, respectively.. Hypoglycaemia (26 %, 33/128) was more common than hyperglycaemia (6 %, 7/128) in all azotemia groups. The activity of AST was significantly higher in the ARF group compared to the CRF group (p = 0.012). Anemia was diagnosed in 41 % and leukocytosis in 28 % (39/142), mainly in the renal group (25/39). Serology revealed a positive titer against Encephalitozoon cuniculi in 40 of 59 rabbits. Acidic pH of the urine was found in 52 % (40/77) of the rabbits. Half of the animals in the CRF group had a urine specific gravity between 1.011 to 1.016. In 58 % (45/78) of the urine samples protein, in 84 % (67/80) blood and in 12 % (9/77) leukocytes were detected by urine dipstick. Erythrocytes were found in 80 % (56/70) and leukocytes in 60 % (41/68) of the urine samples during microscopic examination. Radiographic findings of rabbits with azotemia were kidney conglomerates (9/29), renal sludge (8/29) and a combination of both (7/29). In two rabbits a calcified aorta was detected, in one case accompanied with a generalized osteosclerosis. 67 % (108/161) of the rabbits died or were euthanized due to a poor general condition or a poor prognosis, 25 % (40/161) of the rabbits were released. In all rabbits with prerenal and post renal azotemia creatinine and urea concentrations decreased during treatment or after removal of the obstruction. Additional diseases were found in 70 % (112/161) of the rabbits. Diseases of the gastrointestinal tract (30/135) and the central/peripheral nervous system (28/135) occurred more frequently. Predominantly inflammatory renal changes were found during post mortems of 57 rabbits (37/57), followed by degenerative changes (20/57).