Abstract

Marine debris such as plastic and other foreign objects are commonly found in wild odontocete stomachs at necropsy, but due to the often small amounts and diversity of the debris, the impact on animal health is unclear.¹ Dolphins under human care have also been known to ingest foreign material.The direct and indirect pathologic effects of foreign material ingestion have been well documented.² However, the underlying cause of pica has yet to be elucidated.² Some clinicians would classify pica in small odontocetes as a behavioral disorder or secondary to a primary medical problem.³ An alternate hypothesis was explained to the author in 1999 by Dr. Jim McBain. "The Toy Chest Hypothesis" suggests that dolphins, much like a young dog, explore their environment orally and will play with novel items. Sometimes such items are ingested. Once ingested, odontocetes have the unique ability to regurgitate ingesta from the forestomach.

For most cetacean preventative medical programs, careful gastrointestinal monitoring is common practice. Gastrointestinal monitoring at Dolphin Quest consists of quarterly blood work, monthly gastric cytological analysis, and monthly voluntary gastroesophageal endoscopies. This year, Dolphin Quest added routine gastric ultrasound examination to monitor any presence and number of suspected gastric foreign bodies, and document any daily fluctuations. This non-invasive technique is easy to implement and is used regularly to guide case management.

Abdominal ultrasound imaging has been described for cetaceans.⁶ Consistent orientation and labeling are necessary for systemic approach. Abdominal imaging consisted of interrogation of the entire cranial abdomen with a macroconvex, variable 2–6 megahertz transducer. Focal zones were set at the area of interest and adjusted as needed. When imaged from the left ventrolateral aspect, the forestomach and glandular stomach are easily identified (Figure 1). The glandular stomach is situated just caudal to the liver and somewhat ventral in the abdomen. The forestomach lies caudal and dorsal to the glandular stomach. The pylorus is well seen on the right ventrolateral aspect of the cranial abdomen (Figure 2). Over the period of 2 months, 3 animals at Dolphin Quest Facilities were monitored for the presence of foreign material in the forestomach via abdominal ultrasound. Presence of foreign material was characterized generally by a curvilinear hyperechoic line with a strong distal acoustic shadowing. All gastric foreign material observed was confined to the forestomach. Examination time ranged from 2 to 5 minutes. Visualization and documentation facilitated by voluntarily hydrating the patient with fluids through and orogastric tube (approx. 1.5 liters) directly prior to ultrasound exam (Figure 3). Animals were scanned daily to every other day if scans were positive for gastric foreign material on previous scans. Animals were scanned weekly if the scans were negative for gastric foreign material on previous scans. Case examples, review of the gastric foreign body ultrasound log will be discussed.

Figure 1. Left ventrolateral paramedian plane image of the cranial abdomen with cranial to the left The liver, glandular and forestomach are well seen.

Figure 2. Right ventrolateral dorsal plane image of the cranial abdomen with cranial to the left The image marker has been misplaced on the right of the screen. The pylorus (PYL), forestomach (FS) and glandular stomach (2nd Chamber) are visualized. The label for the pylorus is placed along the ventral wall. The pylorus is filled with echogenic fluid. A foreign body is present in the forestomach. The liver can be seen just cranial to the pylorus.

Figure 3. Left ventrolateral aspect dorsal plane image of the cranial abdomen with cranial to the left The forestomach is mildly distended with echogenic fluid. An approximately 4 cm in diameter nut foreign body.

Acknowledgements

The authors wish to thank Katie Rice, Julie Rocho-Levine, and all of the animal care staff and wonderful animals in the Dolphin Quest Family.

* Presenting author

Works Cited

References 4 and 5 are not cited in the text.

1.  Krzyszczyk E, Kopps AM, Bacher K, et al. A report on six cases of seagrass-associated gastric impaction in bottlenose dolphins (Tursiops sp.). Marine Mammal Science. 2013;29(3):548–554.

2.  Walker WA, Coe JM. Survey of marine debris ingestion of odontocete cetaceans. In: Proceedings from the Second International Conference on Marine Debris, Southwest Fisheries Science Center, NOAA; 1989.

3.  Van Bonn W, Poll C, Meiselman M, Van Valkenburg R, Boehm J. Medical management of chronic emesis in a juvenile white whale (Delphinapterus leucas). In: Proceedings from the 37th Annual IAAAM Conference; May 6–10, 2006; Nassau, Bahamas.

4.  Walsh MT, Friday RB, Johnson AB, Messinger D. Regurgitation in cetaceans: medical implications. In: Proceedings from the 27th Annual IAAAM Conference; 1996; Chattanooga, TN, USA.

5.  McBain J. Personal consultation. 1999

6.  Brook F, Van Bonn W, Jensen ED. Ultrasonography. In: Dierauf LA, Gulland FMD, eds. CRC Handbook of Marine Mammal Medicine. 2nd ed. Boca Raton, FL: CRC Press; 2001: 604–606.