Abstract
Megaesophagus is frequently reported in domestic canines and results in ineffective peristalsis and dilation of the esophagus, resulting in regurgitation.1,2 Megaesophagus is also a cause of morbidity and mortality in managed and rehabilitated populations of phocids.3,4,5,6 However, information on treatment options for megaesophagus in phocids is limited.3,4,5,6 A retrospective review of records from three rehabilitation facilities reported a mortality rate of 92% for seals diagnosed with megaesophagus, highlighting the need for exploration of novel treatment options to improve prognosis.4 Sildenafil, a phosphodiesterase-5 inhibitor, has been reported to manage megaesophagus in dogs successfully.7,8 The objective of this study was to describe the clinical signs, imaging findings and medical treatment of megaesophagus in Pacific harbor seals (Phoca vitulina) with sildenafil.
Between 2021 and 2023, three Pacific harbor seal pups admitted to the Vancouver Aquarium Marine Mammal Rescue Society were diagnosed with megaesophagus based on radiographs after showing clinical signs of regurgitation, diarrhea, bloating, slow weight gain and hyporexia. Two cases (cases 1 and 2) showed improvement in radiographic lesions and resolution of clinical signs after treatment with sildenafil 1 mg/kg PO every 12 hours for 14 days and were released. Post-release survival was monitored in case 3 via a satellite-linked transmitter. The third case (case 3) was euthanized due to worsening lethargy, difficulty tube feeding and continued weight loss after seven days of sildenafil treatment. Concurrent treatments for cases 1, 2, and 3 included simethicone 1 mg/kg PO every 12 hours. Additionally, case 3 was treated with maropitant 2 mg/kg PO every 24 hours. Regurgitation in cases 1 and 2 resolved after initiating treatment with sildenafil. Bloating and hyporexia also resolved over the course of the treatment period, and both individuals began to gain weight more consistently. None of the clinical signs returned after medications were discontinued. Case 3’s regurgitation and weight loss persisted despite sildenafil treatment. Sildenafil successfully managed megaesophagus in two of three P. vitulina pups.
This case series highlights that sildenafil may be a potential treatment option for megaesophagus in P. vitulina pups undergoing rehabilitation. Based on a high incidence of cases in various facilities and apparent successful medical treatment, it is hypothesized that megaesophagus is not always a congenital defect but more likely an iatrogenic condition.
Acknowledgements
The authors thank the veterinary technicians, staff, and volunteers at the Vancouver Marine Mammal Rescue Society for their excellent care and assistance with these cases.
*Presenting author
+Student presenter
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