Abstract

Cetaceans have an elaborate upper gastrointestinal anatomy. Numerous submucosal glands line the base of the tongue and the oropharynx. The esophagus is of large diameter relative to body mass and skeletal muscle elements are prominent in the muscularis externa. Myenteric nerve plexi are also reported as particularly abundant throughout the intestinal tract.^1,2 The stomach is multi-compartmented and is exquisitely unique in structure and function. Clinical observations using endoscopy³, sonography⁴, contrast radiography⁵, CT, MRI^6,7 and most recently positive contrast fluoroscopy suggest an elaborately coordinated pattern of motility and flow of intralumenal contents.

We have noted disturbances of the coordinated motility and ingesta flows in cetaceans with a variety of disturbances of homeostasis. These disturbances sometimes lead to clinically significant disruption of the intralumenal chemical milieu manifest as delayed dissolution rates of skeletal or soft tissue elements of ingested food items. Osteobezoar formation, delayed forestomach emptying and mucosal erosion/ulceration are common sequelae.

In addition, cetaceans (as well as other taxa of marine mammals) demonstrate profound control over deliberate emesis. The action does not fit the classic definitions of emesis, vomiting nor regurgitation, although is commonly referred to as either. Perhaps eructation is the more appropriate term, although Dorland defines this as "belching, casting up wind from the stomach through the mouth." Suffice it to say "They puke whenever they want to...".

We describe here the management of a case of chronic emesis in a juvenile white whale that illustrates the above observations and documents the novel diagnostic use of positive contrast fluoroscopy in a whale as well as our experience with infrequently used drug therapies for altering upper gastrointestinal motility or intralumenal biochemistry.

A four-year-old, aquarium born white whale presented with a history of chronic emesis that had recently progressed to significant weight loss and a concurrent foul odor associated with retained ingesta. The animal had been frequently observed "regurgitating" or "vomiting" whole food items after training sessions. Oftentimes a cloud of liquid ingesta was also produced along with the whole food items and the activity was sometimes observed at times other than immediately following a training session. The food items would often be re-ingested and sometimes ingested by in-contact animals. Other animals in the shared habitat including mature wild born animals were also observed demonstrating this activity, however, this animal appeared to engage in the activity more frequently.

Results of a complete physical examination, CBC, serum chemistry profile, blood cultures and fecal cytological and biochemical analyses revealed a mild to moderate inflammatory hemogram during the time course of treatment but did not elucidate a specific underlying etiology. Multiple diagnostic endoscopic examinations of the upper gastrointestinal tract (in-water under behavioral control and out of water on deck) and sonographic examinations, confirmed delayed forestomach emptying and the periodic retention of liquid ingesta and whole food items in the thoracic esophagus. When items were present in the esophagus there was often an associated rancid foul odor--suggesting oxidation of fats.

C-arm fluoroscopy with positive contrast was utilized to confirm patency of the upper gastrointestinal tract, evaluate the outflow tract and rule out foreign body obstruction.

The animal responded favorably to an intensive treatment regime that included parenteral and oral antibiotics and antifungals (indicated due to concerns over opportunistic infection), oral fluoxetine, metoclopramide, cisapride, and pancreatic enzyme supplementation. In addition food fish were filleted and the feeding schedule was adjusted to include an increased number of small meal offerings.

During the treatment period the animal's body weight increased from a low of 259.5 kg to 437.3 kg. The frequency of the emesis was reduced and the delayed forestomach emptying resolved. All medication doses were slowly reduced over time and currently all but fluoxetine have been discontinued. The animal continues to demonstrate deliberate emesis but the activity frequency has reduced and the whale has remained clinically normal in all other respects to date.

References

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2.  Simpson JG, MB Gardner. 1972. Comparative microscopic anatomy of selected marine mammals. In Biology and medicine, S.H. Ridgway (ed.). Charles C Thomas, Springfield, IL, pp. 298-418.

3.  Dover SH, W van Bonn. 2001. Principles of Endoscopy in Marine Mammals. In: Dierauf, L., F. Gulland (eds.) Marine Mammal Medicine 2nd Edition. CRC Press. Boca Raton, FL. pp.621-641.

4.  Brook F, W van Bonn, E Jensen. 2001. Ultrasonography. In: Dierauf, L., F. Gulland (eds.) Marine Mammal Medicine 2nd Edition. CRC Press. Boca Raton, FL. Pp. 593-619.

5.  Applegate W, W van Bonn, E Jensen. Advances in Tursiops Radiography. International Association for Aquatic Animal Medicine Proceedings VOL 27, 1996. pp. 45-46.

6.  van Bonn W, ED Jensen. 2001. Radiology, Computerized Tomography, and Magnetic Resonance Imaging. In Dierauf, L., F. Gulland (eds.) Marine Mammal Medicine 2nd Edition. CRC Press. Boca Raton, FL. Pp.557-591.

7.  van Bonn W, ED Jensen, WG Miller, HM Lang, SH Ridgway. 2000. Clinical Magnetic Resonance imaging reference anatomy of Tursiops truncatus. Proceedings AAZV and IAAAM Joint Conference. Pp. 558-560.