Marine Mammal Radiology, San Francisco, CA, USA; Animal Internal Medicine and Specialty Services, San Francisco, CA, USA; Animal Scan, Redwood City, CA, USA
When presented with acute gastrointestinal disease, one of the main clinical questions is whether or not surgical intervention is warranted. Diagnosis of gastrointestinal disease in zoo and wildlife species has the added challenge of species-specific anatomic variations. However, valuable clinical information can be obtained through the appropriate application of diagnostic-imaging modalities used in a step-wise approach. Beyond radiography and ultrasound that are often available in-house, advanced imaging modalities may be very useful in individual cases. An understanding of the basic physics behind each modality and the associated limitations, including size limitations, allows appropriate study selection. Developing an in-house imaging library is very valuable for comparison but even when not available, the application of some basic rules can help determine whether or not surgical intervention is warranted. Identifying markedly different intestinal diameters suggesting complete obstruction or free gas suggestive of perforation on radiographs warrants surgical intervention, although ultrasound may provide additional information via a non-invasive route prior to a surgical procedure, particularly in geriatric animals where neoplasia may be a concern. In the case of partial obstructions due to foreign material ingestion, these may be successfully monitored during transit using an appropriate imaging technique, thus avoiding unnecessary invasive procedures in some cases. Gastrointestinal neoplasia, if treated, will often require serial studies and appropriate modality selection for comparison over time is needed. In addition to modality-specific limitations and applications, repeatability, transportation, cost, and time needed under anesthesia are all factors that need consideration on a case-by-case basis.