Diagnostics

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The use of computed tomography (CT), though not readily available at every institution, is becoming a more widespread modality for use in the small animal patient. Computed tomography affords a rapid evaluation of skeletal images with a small slice thickness that can be as small as 0.625.

Abdominal radiographs are a rapid, readily available method to give an overview of the abdomen. Though most people believe ultrasound is the new modality of choice for abdominal evaluation, the limitations of ultrasound not being able to penetrate gas as well as the technical ability and time to acquire images still make abdominal radiographs a great first modality in the patient with acute abdominal pain.

The explosion of magnetic resonance imaging (MRI) has revolutionized neuroimaging. However, other modalities still are valuable when looking at the central nervous system. These include ultrasound and computed tomography (CT). Radiographs have limited usefulness due to the superimposition of structures associated with the cranial vault and vertebral column.

The use of radiography to examine the abdomen is full of complications. Radiographs are very good at determining the difference between bone and gas, but soft tissue and fluid are the same opacity. When dealing with intra-abdominal lesions, the main goal is to differentiate one soft tissue mass from a normal soft tissue structure from abdominal fluid. Ultrasound uses high frequency sound waves to accomplish what radiographs cannot.

Ultrasound examinations are becoming routine standard of care in veterinary medicine. Due to the non-invasive nature of the modality, the general affordability of the hardware and the growing amount of continuing education to train general practitioners and veterinary technicians on the technical aspects of scanning, ultrasound is becoming the modality of choice, especially when examining the abdomen.

Recognizing that thoracic radiography is the first diagnostic imaging step for dogs and cats with thoracic disease, there is a lot more to thoracic imaging than radiographs. In specific circumstances additional modalities which may be considered include ultrasound, computed tomography (CT), fluoroscopy and nuclear scintigraphy.

Diagnostic imaging has seen a huge technology shift in the last 10 years. Modalities that were not accessible to the small animal patient, such as magnetic resonance imaging, are now considered the modality of choice for neurologic examinations. This technology shift has caused a lot of confusion as well as questions about what modalities are used for which diseases and why.

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Aside from ultrasound, a digital radiography suite is going to be the most expensive upgrade for the private practitioner in the realm of diagnostic imaging. However, this expense will be well worth the investment from a diagnostic imaging standpoint. After more than a century of film and film screen imaging, the backdrop of diagnostic radiology has changed from hanging films on view boxes to LCD monitors.

Obvious thoracic disease need not be discussed here. Fulminating heart failure, pneumonia, advanced metastatic lung disease, severe pneumothorax and pleural effusion are reliably diagnosed radiographically. What I would like to share with you are the less obvious radiographic manifestations of acute cardio-respiratory disease and my approach to diagnosis. And remember, in the final assessment much can be learned from the presenting clinical signs. Does the patient have a cardiac murmur or history of heart disease? Was there an observed or suspected trauma?

Much can be learned about the gastrointestinal tact (GIT) by careful evaluation of survey abdominal radiographs. Survey radiographs of the abdomen in cases of GIT disease should always include the stomach, liver, and diaphragm. Stomach position, size, shape and contents are evaluated. The small intestine is assessed for position and distribution within the abdominal cavity, diameter, and luminal contents.