Successful treatment of megaesophagus with sildenafil in juvenile Pacific harbor seals (Phoca vitulina richardii) undergoing rehabilitation.

OBJECTIVE

To describe the outcome of megaesophagus in harbor seal pups undergoing rehabilitation from January 2021 to December 2023.

METHODS

5 harbor seal (Phoca vitulina richardii) pups, 2 males and 3 females, were included in the study. All 5 cases had no clinical signs associated with megaesophagus on initial presentation to the rehabilitation facility. Case 1 presented with regurgitation, diarrhea, bloating, and poor gain of body mass starting 24 days into rehabilitation. Case 2 presented with regurgitation and bloating on day 12. Case 3 presented with hyporexia, bloating, poor gain of body mass, and regurgitation between days 55 and 60. Case 4 presented with lethargy, diarrhea, and regurgitation starting on day 12 of rehabilitation. Case 5 presented with difficulty gavage feeding 14 days into rehabilitation and regurgitation starting day 28. Radiographs in all 3 cases revealed dilation of the esophagus and gas distention of the stomach and intestines, consistent with megaesophagus. Cases 1, 2, and 3 were treated with 1 mg/kg sildenafil by mouth every 12 hours for 14 days at the time of diagnosis.

RESULTS

Cases 1 and 2 showed improvement in radiographic lesions and resolution of clinical signs after treatment and were released after 1 and 3 months of posttreatment monitoring respectively. None of the clinical signs returned after medications were discontinued. Postrelease survival was monitored in case 2 via a satellite-linked transmitter for 39 days. Case 3 was euthanized due to worsening lethargy, difficulty tube feeding, and continued loss of body mass after 6 days of treatment. Case 4 was euthanized at the time of diagnosis of megaesophagus on radiographs due to dull mentation and declining clinical status, and case 5 died a few hours after diagnosis of megaesophagus on radiographs before sildenafil treatment could be initiated.

CONCLUSIONS

Sildenafil successfully managed megaesophagus in 2 of 3 P vitulina richardii juveniles. This case series highlights that sildenafil may be a potential treatment option for megaesophagus in P vitulina richardii pups undergoing rehabilitation.

CLINICAL RELEVANCE: Based on the results of these cases, it is hypothesized that megaesophagus in rehabilitated harbor seals is not always a congenital defect but possibly an iatrogenic condition.