CVC highlight: When to refer for advanced imaging—and when not to - Veterinary Medicine
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CVC highlight: When to refer for advanced imaging—and when not to
Which form of imaging is most helpful in which cases? Read on to find out.


Dr. King performing ultrasonography on a patient. (Photo by Andrew Cunningham, Cummings School of Veterinary Medicine at Tufts University.)
The opportunity to refer cases for advanced imaging on an inpatient and outpatient basis is increasing rapidly. Many referral hospitals now offer outpatient ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI).

Key to a successful patient referral for diagnostic imaging is managing owner expectations. Cost, risks, benefits, diagnostic expectations, and the limited ability to perform interventional procedures on outpatient cases should be discussed before referral. The following tells how to determine the best modality for your patient as well as which cases are appropriate for inpatient and outpatient imaging.


From an imaging perpective, an outpatient is one being referred exclusively for an imaging diagnosis. This situation is ideal for clients looking to follow up with their regular veterinarian for further diagnostics or treatment. However, the lack of familiarity and lack of a doctor-client-patient relationship may preclude the use of sedatives and interventional procedures.

Alternatively, from an imaging perspective, an inpatient is simply one that has met with, and been examined by, a doctor in the specialty practice. Although this may yield a more thorough and complete consultation, and may allow use of medications, interventions, and treatments, this type of referral tends to be more costly.

Some specialty practices offer a mixed model in which a patient is referred exclusively for diagnostic imaging but receives a brief physical examination and assessment by a specialty practice doctor so that sedation or anesthesia can be performed. This model is particularly common at outpatient CT and MRI centers. A discussion with the specialty center before referral will help determine which imaging modality and referral type is best for an individual patient.


It is best practice to instruct owners to fast the patient before an ultrasonographic examination. This prevents a food-filled stomach from obscuring visualization of the abdomen and also allows for safe use of sedation if deemed necessary. Ideally, fractious, uncooperative, or aggressive patients are best suited for inpatient referral to allow for adequate observation after the use of sedation, anesthesia, or both. However, sedation will likely not be given for outpatient cases; thus, fractious, uncooperative, aggressive patients are best suited for inpatient referral.

Ultrasonographic examinations are becoming more commonplace in veterinary medicine and can be a useful tool in certain situations. In managing an owner's expectations, it is crucial to communicate that the majority of ultrasonographic findings are nonspecific, and additional diagnostic steps are often required to obtain a definitive diagnosis.


These cases are likely the least appropriate outpatient referral cases since 80% leave outpatient imaging for hepatic disease without a diagnosis. A biopsy or aspirate is often required to establish a definitive diagnosis. Exceptions would be gallbladder and biliary disease (e.g. gallbladder mucocele, cholelithiasis, obstruction) in which abdominal ultrasonography may be a definitive test. Patients with suspected portosystemic shunts should be referred for inpatient ultrasonography since they may require sedation or further diagnostic tests.


Ultrasonography of the spleen is most often performed to detect a mass. However, it can be difficult to assess whether the mass is benign or malignant with ultrasonography, and rarely can a definitive diagnosis be reached without further diagnostics (e.g. fine-needle aspiration, biopsy).

Urinary system

Suspected ureteroliths, cystoliths, pyelonephritis, ectopic ureters, prostatic abscesses, and cysts make ideal referral ultrasonography cases. A definitive diagnosis can often be reached based on imaging findings.

Gastrointestinal system

The utility of ultrasonographic examination of the gastrointestinal tract varies. Foreign bodies can be the most straightforward diagnosis, whereas inflammatory and neoplastic diseases are the least straightforward because of the overlap in ultrasonographic appearance. Generally, further testing in the way of ultrasound-guided diagnostic techniques, endoscopy, or laparoscopic or abdominal exploratory surgery may be necessary to distinguish between these two disease entities and to differentiate the types of neoplasia.


Since it is impractical to examine the entire thorax ultrasonographically, a targeted approach based on radiographic findings is usually employed. Although pleural effusion is easily detected and characterized, rarely is a definitive cause found on ultrasonography.

Pulmonary nodules may be detected if they are located peripherally. In these cases, ultrasonography is used to help guide fine-needle aspiration or biopsy to help make a definitive diagnosis.


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