Renal papillary necrosis in horses after phenylbutazone and water deprivation.

Acute renal papillary necrosis occurred in five horses given normal therapeutic doses of phenylbutazone and deprived of water for 36 to 48 hours prior to euthanasia. Five horses given phenylbutazone alone and four horses subjected to water deprivation alone did not develop papillary necrosis. Urinalyses were normal prior to water deprivation, and also after water deprivation in the horses that did not receive phenylbutazone, but the water-deprived, phenylbutazone-treated horses had many red blood cells, transitional epithelial cells, and large numbers of oxalate crystals in their urine. Ulceration of the alimentary tract was seen in more than 50% of these horses. Tongue ulceration was present in one of five horses given phenylbutazone and one of five horses which had phenylbutazone and water deprivation. Ulceration of the gastric mucosa was seen in two of the five phenylbutazone-treated horses, four of five horses with phenylbutazone treatment and water deprivation, and one of four horses with water deprivation alone. Severe colonic ulceration with perforation and peritonitis was present in one horse given phenylbutazone for three months. No other significant changes in the small or large intestine were seen in the other 13 horses.