HISTORY

A free-ranging adult 1.2 kg female emerald tree boa (Corallus caninus) was imported in 1999. Since then it was one of a reptile collection exhibited at the Zoo Aquarium, Madrid. The first sign of overt clinical disease in this snake was a reduced appetite, refusing the last two meals. Several weeks later, the snake was discovered on the floor of the terrarium, showing a cloacal prolapse. On physical examination the snake was severely dehydrated and depressed. The prolapsed tissue was firm and partially necrotic. The prolapse was reduced by external pulsion, and the snake was treated with enrofloxacin (5 mg/kg IM) and rehydrated with lactated Ringer solution (25 ml/kg IC). Palpation revealed a firm mass 7-10 cm cranially to the cloaca. The snake was prepared for an exploratory laparotomy but it died two hours later.

At necropsy, a severe intestinal intussusception was observed 10 cm cranially to the cloaca. At the same level, a firm, round (5 mm in diameter) mass was observed adhered to the coelomic wall. Several firm, round (1-4 mm in diameter), white nodules were observed in the liver and kidneys.

Samples from small intestine, colon, coelomic wall, heart, liver, kidneys, lung, pancreas and spleen were collected, fixed in neutral buffered 10% formalin, routinely processed for light microscopy, and stained with hematoxylin and eosin. Histopathology revealed an intestinal papillary adenocarcinoma with metastases in both kidneys, liver, lung, and coelomic wall.

DISCUSSION

Spontaneous neoplasia of the gastrointestinal tract is reported infrequently in snakes in comparison to domesticated animals. Neoplasms of unspecified intestinal origin have been reported in a canebrake rattlesnake (Crotalus horridus atricaudatus), timber rattlesnake (Crotalus horridus horridus), and black rat snake (Elaphe obsoleta). Two neoplasms in bullsnakes (Pituophis melanoleucus catenifer) were of colonic origin. Five neoplasms of cloacal origin also have been reported: two colonic adenocarcinomas in corn snakes (Elaphe guttata guttata), two transitional cell carcinomas in reticulated pythons (Python reticulatus), and a squamous cell carcinoma in an eastern garter snake (Thamnophis sirtalis sirtalis).

Prolapse of the colon is generally secondary to tenesmus. Intestinal intussusception was detected in this case; it occurred secondary to stricture of the intestinal lumen from thickening of the bowel wall by neoplastic cell infiltration. This is the first report of a metastatic intestinal adenocarcinoma in a snake. To date, carcinomas of the reptilian lower alimentary tract had not been reported to metastasize, and consequently, surgical resection has been the treatment of choice. However, our snake showed numerous metastases in liver, both kidneys, and lung. Prior to the surgical resection of intestinal carcinomas in snakes, evaluation of the hepatic and renal function, ultrasonography, and/or laparotomy may be advisable in order to detect visceral metastases.