Abstract. Thirty-five cases of renal medullary crest necrosis morphologically similar to the renal papillary necrosis of analgesic nephropathy as described in man and rats are reported in horses receiving maintenance dosages of phenylbutazone. The primary lesion is a well-demarcated focal medullary necrosis resulting in sequestration of fragments of the renal crest. Renal cortical lesions are considered secondary to the medullary necrosis and consist of segmental pallor as a result of tubular dilatation, filtrate retention, and interstitial edema. Ischemia in concert with phenylbutazone is suggested as the etiology. Renal medullary crest necrosis is presented as more appropriate morphological terminology for this lesion in the equine species than renal papillary necrosis as is used in man and rats.The nephrotoxicity of non-steroidal anti-inflammatory drugs in man is well known [8,12, 191. The drugs most commonly implicated in analgesic nephropathy are aspirin, phenacetin, and caffeine [ 121, although the phenylalkalonic acids fenoprofen, naproxen, and phenylbutazone also are incriminated [6, 1 1, 12, 181. A characteristic lesion of analgesic nephropathy is renal papillary necrosis [8,12, 191, and this lesion has been produced experimentally in rats with phenylbutazone and indomethacin [ I , 21 and in rats and rabbits with phenacetin and salicylates [ 3 , 101 and demonstrated to be the result of medullary ischemia [9, 131. Phenylbutazone is the most popular and widely used non-steroidal anti-inflammatory agent in equine medicine [4,7, 16, 171; however, morphological lesions associated with phenylbutazone toxicity in horses have been reported only rarely [5. 14, 151. Experimentally induced phenylbutazone toxicity in ponies has resulted in oral, gastric, duodenal, cecal, and colonic ulcers [ 14, 151. In an unrelated study in Thoroughbred and Standardbred horses, phenylbutazone produced oral and gastric ulcers in two horses [ 5 ] . Necrotizing phlebitis of the portal vein also was attributed to phenylbutazone toxicity [5].Although renal lesions commonly are ascribed to analgesic toxicities in man [8, 121 and rats [ l , 2, lo], no morphological lesions associated with the clinical use of phenylbutazone have been described in the kidneys of horses. The purpose of this paper is to report the spontaneous occurrence in 35 horses of renal medullary crest 662

Sixteen normal 20 to 30 kg dogs had standard femoral head and neck excision (8 dogs) or femoral head and neck excision with interposition of a biceps muscle flap (8 dogs). Lameness lessened at week 6, and did not differ between groups; neither group returned to a completely normal gait. Weightbearing decreased on the operated pelvic limb compared to controls (forceplate analysis). Weightbearing force of the muscle flap dogs was significantly less at weeks 6 and 16 than that of the standard femoral head and neck excision dogs. The operated limb of both groups was shortened; shortening was significantly greater for the muscle flap group. Hip extension was limited in both groups. Both groups had decreased (more acute) hip, stifle, and hock angles measured in standing position. Thigh muscle atrophy was more pronounced in the muscle flap group at week 6. More soft tissue was interposed in the muscle flap group at necropsy compared to the group with standard femoral head and neck excision, but the difference was not statistically significant. Skeletal muscle fibers were present in the interposed fibrous connective tissue of the muscle flap group, and the healed surfaces were smoother than those of the standard femoral head and neck excision group.

The macroscopic and microscopic features of a uriniferous perirenal pseudocyst in a castrated male 12-year-old American Domestic Short Hair cat are characterized. The development in humans and animals of a perirenal pseudocyst due to the accumulation of urine, lymph, or blood is discussed. In the presented case, microscopic evidence suggests that the pseudocyst developed following formation of a split in the kidney capsule. Emphasis is placed on the development of uriniferous pseudocysts and three proposed criteria for their development: trauma, abnormal openings that allow extravasation of urine, or urethral obstruction.

Diagnostic imaging, including computed tomography, of a two-month-old foal with renal failure indicated that its right kidney was probably absent and that its left kidney was abnormal in shape. The foal was stabilised and released, but three days later its clinical signs recurred. Postmortem examination revealed renal hypoplasia and dysplasia, the first reported case of this condition in an American miniature horse.

An 11-year-old, female domestic longhair was presented for dyspnea, vomiting, and left forelimb lameness. A mass in the left caudal lung lobe was seen on thoracic radiographs. The mass was resected during thoracotomy, and histopathology confirmed a diagnosis of endogenous lipid pneumonia. The cat recovered slowly from surgery and was euthanized 11 days following discharge because of persistent respiratory difficulties. Necropsy findings included lipid pneumonia and bronchogenic carcinoma, with probable tumor metastasis to the small intestine, spleen, kidney, and left triceps muscle.