Abstract
Shedd Aquarium has a long history of accepting rescued and rehabilitated Alaska and Northern sea otters that are deemed non-releasable by the United States Fish and Wildlife Service. Of the six female Northern (Enhydra lutris lutris) and Alaska (Enhydra lutris kenyoni) sea otters that have been in the current or historical collection since 1989, three have been diagnosed with uterine leiomyomas. The otters were rescued as pups from various locations in Alaska, rehabilitated locally and then transported to Shedd for permanent care. All were nulliparous despite being housed in groups that included an intact male. All had antemortem diagnosis and treatment via imaging (radiography, ultrasonography, CT scan +/- MRI), surgical resection and histopathology. Radiography confirmed soft tissue masses with mixed echogenicity on ultrasound. Percutaneous fine needle aspirates and core biopsies were typically non-diagnostic. Surgical approach and technique were like those used in small, domestic species except for surgical site preparation. Due to its importance in thermoregulation in these species, hair was not clipped. After disinfection with alternating povidone iodine solution and alcohol, the hair was parted with a sterile comb and a mix of sterile lubricant and povidone iodine solution applied. Case 1 at time of diagnosis was an 18-year-old Northern sea otter. Staff noticed a firm right caudal abdominal swelling that was freely moveable upon palpation. The right uterine horn containing the mass was removed at surgery on 27 September 2007. At necropsy five years later, there was no evidence of tumor regrowth at the surgical site, but the remaining left uterine horn did contain a 4.5x4x2.5 cm leiomyoma. Case 2 at time of diagnosis was a 10-year-old Alaska sea otter. A large right-sided abdominal mass was found incidentally on survey radiographs during an evaluation for nasal ascariasis. The right uterine horn containing the mass was surgically removed on 6 May 2015. The animal is still clinically healthy. Case 3 at time of diagnosis was a 14.5-year-old Alaska sea otter. Multiple firm masses in the left and caudal abdomen were palpated and imaged during routine preventive examination and confirmed via CT scan. An ovariohysterectomy was performed on 11 January 2017. Histopathology revealed four uterine leiomyomas and moderate cystic endometrial hyperplasia. While leiomyomas and/or reproductive tract tumors have been found in wild sea otters, the incidence reported is low.1-6 Although these slow-growing tumors of smooth muscle origin are typically benign, they can become space-occupying, highlighting the importance of routine preventive examination for early detection and resection. Complete surgical resection is typically curative. Leiomyomas in other species can be influenced by the interaction of sex steroid hormones and growth factors.7-9 As a result, ovariohysterectomy has historically been recommended to prevent and control recurrence in dogs.10 Given the high frequency seen in this small population of sea otters, further discussion of prophylactic ovariectomy/ovariohysterectomy for non-breeding animals should be pursued.
Acknowledgements
The authors want to acknowledge and sincerely thank the talented and caring staff of the Animal Health and Marine Mammal Departments at the John G. Shedd Aquarium for their dedication to the highest standards of animal care and welfare. Special thanks go out to the otter team and to the veterinary technicians. The authors also thank veterinary surgeon Dr. Mitch Robbins, veterinary radiologist Dr. Hylton Gelb and the staff at the Buffalo Grove Veterinary Specialty Center for their generous donation of resources and expertise. The authors acknowledge the pathology services and insight provided by the University of Illinois College of Veterinary Medicine’s Zoological Pathology Program.
* Presenting author
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