A carcass of male Royal Bengal tiger, around three years of age, with a clinical history that the animal was anorectic and dull, and given symptomatic treatment for three days was referred to the Institute of Animal Health and Veterinary Biologicals, Bangalore for necropsy examination. The animal had died in the early hours of the previous day. The necropsy was conducted about seven hours after the death. The animal was fairly good in condition except for the rough appearance of the hair coat. There were no external wounds on the body. The visible mucous membranes were pale and slightly icteric. There was abundant subcutaneous fat. The peritoneal cavity was distended with approximately two litres of ascitic fluid. The subcutaneous tissue was slightly icteric. There was biliary imbibition on the liver parenchyma, stomach and a part of small intestine. The urinary bladder was distended with approximately one litre of straw-coloured urine. The kidneys were highly enlarged and appeared as a sac filled with fluids. On incision, about one litre of serous fluid oozed out. The capsule was hard to peal. The cortex was compressed with multiple interconnected cavities. The medullary area was increased with cortex appearing as a band (Fig. 1). The Liver, spleen, lungs, heart, stomach and intestines did not show any changes of pathological significance. Based on the gross finding, the necropsy diagnosis of chronic hydronephrosis was made.

Histologically, highly congested and focal areas of haemorrhages were noticed in the kidneys. The capillary tufts of the glomerulus were shrunken with increased Bowman‘s space. The tubular epithelium showed necrotic changes with tubules obliterated and highly compressed. Extensive proliferation of connective tissue between the tubules and areas of mononuclear cell infiltration around the blood vessels were observed (Fig. 2). The blood vessels showed medial thickening. The histopathological findings indicated chronic interstitial nephritis.

Urinary tract obstructions that are chronic in nature are the most likely cause of the hydronephrosis. However, the extent and the duration of obstruction are important in determining the severity of the renal lesions¹. Chronic or partial obstruction causes progressive distension of the renal pelvis and pressure atrophy of the renal parenchyma. In the present report, the histological observations that indicated the chronic interstitial nephritis might have led to hydronephrosis. The interstitial nephritis is generally observed in cases of toxicosis due to heavy metal poisoning. Since the tiger belongs to the National Park such a possibility of its exposure to certain toxic materials is remote. Further, the perusal of literature showed that there were no reports on hydronephrosis in tigers except for one report of nephritis and pyelonephritis based on ultrasonography and gross lesions². Hence, this report appears to be the first report of hydronephrosis in a Bengal tiger.

Fig. 1:Tiger Kidney: The cortex showing multiple interconnected cavities with increased medullary area.

Fig. 2:Photomicrograph of the kidney showing extensive proliferation of connective tissue between the tubules and areas of mononuclear cell infiltration around the blood vessels. HE. × 100

A case of hydronephrosis in a tiger