Necropsy of a Sulcata Tortoise (Geochelone sulcate) with Urinary Calculi
By Will Sims, DVM, MS
An eight-month-old sulcate tortoise was submitted to the Texas A&M Veterinary Medical Diagnostic Laboratory’s (TVMDL) Amarillo laboratory for necropsy. The history indicated that the tortoise had died unexpectedly with a history of bloating and a progressively soft shell. No clinical diagnosis was made by the referring veterinarian. A popular pet for reptile lovers, the sulcate tortoise, Geochelone sulcate, also known as the African spurred tortoise, can grow up to 36 inches in length and weigh more than 200 pounds. The juvenile tortoise submitted to TVMDL was no larger than a deck of cards and weighed only a few grams. With no working clinical diagnosis, there are numerous possible causes of sudden death in reptiles ranging from an infection to an underlying metabolic disorder.
Necropsy of tortoises and turtles presents a unique challenge to the pathologist as the only way to access the internal organs is by removing the hard shell. A Stryker saw was used to cut the bridges between the carapace (upper shell) and plastron (lower shell) and a scalpel blade was used to separate the skin from the shell. This allowed for the removal of the plastron and a ventral approach to the internal organs. Reptiles have only one body cavity called the coelomic cavity.
In this tortoise, there was increased clear fluid filling the cavity. At this point, a bacterial culture swab was used to sample the fluid in case it was later suspected to have a bacterial infection. Gross inspection of the coelomic cavity revealed a large, solid, hard, mineralized mass covered by a translucent tissue membrane in the caudal celomic cavity. Based on the location, it was determined that this was a urinary calculi obstructing the cloaca leading to increased fluid in the coelomic cavity and the apparent bloating observed clinically. A retained egg was also considered; however, because the mineralized mass was solid, a urinary calculi was considered more likely. The exact cause of the formation of urinary calculi in tortoises is not known. It is thought to be a combination of dehydration, urine retention, secondary infections from protozoa or bacteria, and a buildup of urates within the bladder that lead to urinary calculi formation. Ante mortem detection is through radiographs, or if large enough, can be palpated. If detected early enough, these may be removed surgically.
To learn more about this case, contact Dr. Will Sims, veterinary pathologist at TVMDL-Amarillo. For more information about TVMDL’s test catalog, visit tvmdl.tamu.edu or call 1.888.646.5624 for the Amarillo laboratory or 1.888.646.5623 for the College Station laboratory.