Abstract
Gastrointestinal torsion is an uncommonly reported complication in sand tiger sharks (Carcharias taurus) that has typically been associated with manual restraint and rotation of the animal 360 degrees.1 In this case involving an adult female sand tiger shark, the first abnormality noted was a visible body wall swelling caudal to the left pectoral fin with no recent history of manual restraint. Gastric dilation and concern for torsion were suspected via ultrasound and inability to pass a gastric tube and confirmed through contrast radiography. Gastric decompression was performed via trocarization prior to exploratory surgery performed 32 hours after initial presentation. Anesthesia was induced with intravascular (IV) propofol and maintained with tricaine methanesulfonate (MS-222) ventilation of the gills and IV propofol and midazolam supplementation. Upon left lateral celiotomy, the stomach was gas distended and torsed clockwise approximately 180 degrees. Following additional decompression of the stomach, it was manually rotated counterclockwise with the aid of an orogastric tube. Following a four-layer closure of the celiotomy site, the shark was transported to a recovery pool where cardiac contractility and rate were monitored via ultrasound, and she was manually walked around the pool in a swimming motion while being ventilated with a recirculating pump. Spontaneous ventilation resumed 3 hours after surgery and voluntary movement increased between 3 and 6 hours postoperatively; however, progressive voluntary swimming never occurred. Six hours postoperatively, the shark was released and monitored closely; however, 16 hours postoperatively, the shark developed increased bruising of the entire ventrum and lethargy, was less responsive to stimulation, and was treated for suspected acidosis. Despite supportive care, the shark continued to decline and was euthanized 32 hours following surgery. Blood gas and biochemistry analyses in the hours preceding death included markedly elevated blood lactate and muscle enzymes (creatine phosphokinase and aspartate transaminase). At necropsy, the stomach was in normal anatomic position without torsion and the celiotomy incision remained sealed with all sutures intact. The major histopathologic diagnoses included multifocal erosive gastritis, locally extensive ulcerative esophagitis, gastric and esophageal edema, and acute multifocal neuronal necrosis within the brain, suggestive of hypoxia. Cause for spontaneous torsion in this shark was not identified, despite review of video footage of the system. Orogastric tubes should be able to be easily passed into the stomach of sand tiger sharks, and when they cannot be, gastric torsion should be suspected. In cases of suspected gastric torsion, prompt surgical intervention is recommended. Thick padding should be used to minimize gravitational injury, and the ventral thorax should be accessible to monitor cardiac rate and contractility intraoperatively. The surgical procedure was straightforward in this case and was significantly aided by the use of an orogastric tube. A lateral surgical approach seemed feasible, although the long-term outcome of that approach is unknown. Clinicians should consider providing aggressive postoperative supportive monitoring and care, including monitoring serial blood lactate and pH with a point-of-care analyzer and providing physical support, fluid therapy, and sodium bicarbonate therapy as indicated for several days postoperatively.
Acknowledgements
The authors wish to thank the New York Aquarium, Bronx Zoo’s Zoological Health Program, and associated animal care staff for all of their efforts and dedication to Carmella.
*Presenting author
+Student presenter
Literature Cited
1. Wyffels JT, George R, Christiansen EF, Clauss TM, Newton AL, Hyatt MW, Buckner C, LePage V, Latson FE, Penfold LM. 2022. Reproductive cycle and periodicity of in situ and aquarium female sand tiger sharks (Carcharias taurus) from the Western North Atlantic. Mar Sci. 2022;9:925749.