Mark D. Stetter, DVM
The numbers of diagnostic procedures available for clinical use in amphibians are limited. Imaging techniques have commonly been confined to radiography. While radiographs create an excellent image of bony structures, they usually provide poor detail of soft tissue structures in amphibians.
Ultrasonography has become an increasingly important technique in veterinary medicine. It provides a noninvasive method for direct imaging of internal tissue anatomy. Ultrasonography is most commonly used for diagnostic examination of soft-tissue structures and for the examination of reproductive anatomy.
Amphibians are well suited for ultrasonography. Their characteristic lack of hair, feathers or scales, provide an ideal surface for unimpaired imaging. Amphibians, to various degrees, live in an aquatic environment. This allows the use of unique underwater scanning techniques which would be unrealistic with terrestrial animals. Clinically ill amphibians commonly develop coelomic fluid accumulation (ascites, anasarca). The presence of this fluid will often enhance the image of internal organ structures.
A variety of techniques can be used for restraining and positioning the animals during ultrasound evaluation. Restraint techniques include either sedation, direct manual restraint or placing the patient in a water-filled plastic container. The transducer can be used in one of three methods: direct probe-toskin, probe-to-water and probe-to-plastic. Coupling gel is utilized for all techniques with the exception of the probe-to water method. The most effective strategy is to place the animal into a water filled plastic container. The probe is than either placed directly in the water or underneath the container with direct contact of the plastic. Two types of containers can be utilized. Flexible plastic containers (zip-lock bags) and rigid plastic containers (clear plastic food storage containers) have both been used. Flexible containers provide a slightly improved image but are more cumbersome to use than the rigid containers which occasionally can produce image artifacts. The use of a plastic restraint device allows excellent patient imaging without the need for sedation or direct manual restraint.