On Thursday, May 27, one of the Zoo’s Gila monsters underwent surgery at 10 a.m. at the Joan Kirkpatrick Animal Hospital to remove a tumor from her kidney tissue.

Native to southwestern United States and northwestern Mexico, Gila monsters are reptiles and named for the Gila River in Arizona. They are covered in beadlike dorsal scales that are black and yellow or pink, and they have a forked tongue that is used to “taste” the air for the presence of food and predators. They are a venomous lizard species. Their venom is used strictly in defense and not for subduing prey as in venomous snakes. With a conservation status of near threatened, Gila monsters are a true treasure to behold.

When the Zoo’s herpetology caretakers noticed signs of lethargy and a change in the geriatric, female Gila monster’s appetite, they immediately contacted the Zoo’s veterinary team. The herpetology care team transported the Gila monster to the Joan Kirkpatrick Animal Hospital on Thursday, May 20, for an initial health check, which consisted of a physical examination, radiographs and bloodwork.

Veterinary team members felt for any abnormalities under the skin of the Gila monster, leading them to discover a hard mass. The presence of the mass and concern for the Gila monster’s ongoing welfare led veterinarians to the decision to move forward with the surgery to determine what kind of mass it was and remove it if possible.

While cancer is common in older reptiles, this was the first case of cancer to be surgically removed from a heloderma, a genus of venomous lizards, at the Zoo’s animal hospital. On the morning of the surgery, the Zoo’s Associate Veterinarian, Dr. Gretchen Cole, performed an exploratory surgery. The Gila monster was monitored throughout the procedure by Veterinary Clinic Coordinator, Liz McCrae, and Veterinary Technician, Julianna Fischler, inside the Joan Kirkpatrick Animal Hospital’s surgery suite. Once the body of the Gila monster was opened, Dr. Cole located the tumor and noticed that it was surrounded by blood vessels, as well as attached to the front of her kidney. Because of the intricacy of the vessels, it took time and precision to carefully remove the tumor from the Gila monster without causing internal damage.

Her surgery took approximately 30 minutes from beginning to end, resulting in the successful removal of the golf-ball-sized tumor. Following the surgery, the Gila monster was monitored daily by caretakers to assess her food and water intake and bowel movements. A biopsy was collected from the mass and sent out to a lab, which determined that it was a kidney tumor. Because kidney tumors are typically slow growing and there was no evidence of metastasis, the development of secondary malignant growths at a distance from a primary site of cancer, the Zoo’s veterinary team was confident that she’d recover.

Today, the Gila monster is mobile and has regained her appetite. Because she is geriatric, the Gila monster will remain behind-the-scenes at the Zoo’s Big Rivers habitat in Oklahoma Trails. The Zoo is also home to a 31-year-old, male Gila monster who is currently on habitat at the Herpetarium.

- Dr. Gretchen Cole, associate veterinarian

Photo: Sabrina Heise and Rae Karpinski