Chronic vomiting (vomiting of more than two weeks' duration) is a common presenting complaint from owners of dogs evaluated
at both primary care hospitals and referral institutions. The order in which diagnostic tests are performed in these cases
is determined not only by the most likely differential diagnoses but also by the perceived answers that could be provided
by each test when balanced with invasiveness, ease, and—of particular importance to owners—cost. For example, ultrasonography
is a rapid, minimally invasive, and widely available technique for evaluating the abdominal cavity. However, this imaging
modality is often cost-prohibitive, particularly with the likelihood of more testing being required afterward. Unfortunately,
no studies have evaluated the utility of abdominal ultrasonography in dogs with chronic vomiting with the goal of identifying
a subset of patients that would most or least benefit from this diagnostic test. The authors of this prospective study hypothesized
that the diagnostic utility of abdominal ultrasonography would be highest in dogs with gastrointestinal neoplasia and lowest
in dogs with chronic inflammatory gastrointestinal disorders, such as inflammatory bowel disease or gastritis.
For this study, a complete blood count, a serum chemistry profile, and abdominal ultrasonography were performed on 89 dogs
with chronic vomiting. A survey radiographic evaluation before ultrasonography was not required or evaluated in this study.
The ultrasonographic evaluation of the gastrointestinal tract included determination of gastric and intestinal wall thickness,
appearance of wall layers, and evaluation of luminal contents, diameter, and motility. The decision of whether histologic
evaluation of gastric or intestinal tissues was needed for a clinical diagnosis, as well as whether tissues were collected
endoscopically or through celiotomy, was at the discretion of the attending clinician. Owners recorded the frequency of vomiting
and diarrhea and any treatments that were administered for a minimum of five months or until patients were euthanized or died.
Monthly evaluation of these logs was required to support presumptive clinical diagnoses and track disease progression. Only
dogs with a final diagnosis of intra-abdominal gastrointestinal tract disease (including the pancreas) as the cause of their
vomiting were included in the final study.
Upon a dog's discharge from the hospital, two clinicians not involved in the evaluation of that particular case were asked
to confirm whether the final clinical diagnosis was correct and, if so, were asked to grade the diagnostic utility of the
ultrasonography results on a five-point scale, ranging from being critically useful (diagnosis was obtained by ultrasonography)
to being associated with a negative result (ultrasonography provided conflicting information or hindered diagnosis).
Both reviewers agreed that in 61 of 89 dogs (68.5%), the diagnostic utility of abdominal ultrasonography was low, meaning
that the same diagnosis would have been reached without results of this imaging modality and that no new information that
contributed to the final diagnosis was obtained. In 20 of 89 dogs (22.5%), both reviewers agreed that abdominal ultrasonography
positively contributed to the final diagnosis. In the final eight dogs (9%), the reviewers disagreed about the usefulness
of the results, and the average score (3.5 out of 5) reflected questionable diagnostic utility.
Chronic inflammatory disorders of the gastrointestinal tract (gastritis or inflammatory bowel disease) were diagnosed in 51
of 89 dogs (57.3%); thus, they were the most common diagnoses in dogs enrolled in this study. Gastrointestinal neoplasia (primary
gastrointestinal lymphoma, gastric adenocarcinoma, and other primary intestinal neoplasms) was the second most common diagnosis
in enrolled dogs, diagnosed in 20 (22.5%) patients. Other diagnoses included pancreatitis, small bowel foreign bodies, duodenal
ulceration, and intussusceptions.
The diagnostic utility of abdominal ultrasonography was lowest in patients with chronic inflammatory disorders, with only
one of the 51 (2%) dogs thought to have ultrasonographic findings that were important in reaching the final diagnosis. The
diagnostic utility of abdominal ultrasonography was judged useful in five of seven (71.4%) dogs with lymphoma and was significantly
higher in dogs with this diagnosis than in dogs with chronic inflammatory disorders. The diagnostic utility of ultrasonography
in dogs with gastric adenocarcinomas was judged useful in three of 10 (30%) dogs and was significantly higher than in dogs
with inflammatory bowel disease but not in those with gastritis or those with concurrent gastritis and inflammatory bowel
disease. Other diagnoses in which abdominal ultrasonography was judged to be useful included pancreatitis (three of three
[100%] dogs), small bowel foreign bodies (two of three [67%] dogs), duodenal ulceration (two of three [67%] dogs), and intussusceptions
(one dog); however, the number of dogs with these diagnoses was too small to allow statistical analysis.
When select patient signalment and historical and physical examination findings were evaluated, the only factors that were
significantly associated with increased diagnostic utility of abdominal ultrasonography were increased patient age (the older
the patient, the more likely that ultrasonography would be judged to be diagnostically useful) and a clinical diagnosis of
gastrointestinal neoplasia. Although the frequency of vomiting and percent of body weight loss were also initially found to
be associated with increased diagnostic utility, these associations were not independent of age or diagnosis. However, despite
the large number of cases in which abdominal ultrasonography was found to not contribute to the final diagnosis, in no case
did results hinder or mislead clinicians.