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).
Dr. King performing ultrasonography on a patient. (Photo by Andrew Cunningham, Cummings School of Veterinary Medicine at
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.
INPATIENT VS. OUTPATIENT
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
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).
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.
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
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.