Todd R. Tams, DVM, DACVIM VCA
Vomiting refers to a forceful ejection of gastric and occasionally proximal small intestinal contents through the mouth. The vomiting act involves three stages: nausea, retching, and vomiting. Serious consequences of vomiting include volume and electrolyte depletion, acid-base imbalance, and aspiration pneumonia.
It is essential that the clinician make a clear differentiation between regurgitation and vomiting at the outset. Regurgitation is defined as passive, retrograde movement of ingested material, usually before it has reached the stomach. Failure to recognize the difference between regurgitation and vomiting often leads to misdiagnosis. Regurgitation may occur immediately after uptake of food or fluids or may be delayed for several hours or more.
Clinical Features Of Vomiting
Because of the wide variety of disorders and stimuli that can cause it, vomiting may present the clinician with a major diagnostic challenge. A complete historical review with emphasis on all body systems is essential for determining a realistic and effective initial work-up plan and treatment protocol. Consideration of the following features is useful in assessing and diagnosing a patient with vomiting: (1) duration of signs,(2) signalment and past pertinent history, (3) environment and diet, (4) systems review (e.g., history of PU/PD, coughing and sneezing, dysuria or dyschezia, etc.), (5) time relation to eating (vomiting of undigested or partially digested food more than 8-10 hours after eating often indicates a gastric motility disorder [more common] or gastric outlet obstruction [less common]), (6) content of the vomitus (food, clear fluid, bile, blood, material with fecal odor), and (7) type and frequency of vomiting (projectile?, chronic intermittent?, cyclic?, morning vomiting only?).
Most Common Causes of Acute or Chronic Vomiting in Dogs First need to Rule-Out
Indigestion (e.g., table scraps, garbage ingestion)
Food adverse reaction (dietary sensitivity)
True food allergy
Intestinal (including Giardia)
Drug related problems
NSAIDS must always be considered
Other drugs (e.g., cardiac glycosides, antibiotics, chemotherapeutic agents)
Rule-Outs for Chronic Vomiting, once the Causes listed above are Ruled Out (Main categories)
Inflammatory bowel disease
Hypertrophic gastropathy (uncommon)
Intermittent Chronic Vomiting
Chronic intermittent vomiting is a common presenting complaint in veterinary medicine. Often there is no specific time relation to eating, the content of the vomitus varies, and the occurrence of vomiting may be very cyclic in nature. Depending on the disorder, other signs such as diarrhea, lethargy, inappetence, and salivation (nausea) may occur as well. When presented with this pattern of clinical signs, the clinician should strongly consider chronic gastritis, inflammatory bowel disease, irritable bowel syndrome, and a gastric motility disorder as leading differential diagnoses. A detailed work-up including gastric and intestinal biopsies is often required for definitive diagnosis in these cases. It is important to note that chronic intermittent vomiting is a common clinical sign of inflammatory bowel disease in both dogs and cats. Vomiting from systemic or metabolic causes may be an acute or chronic sign and generally there is no direct correlation with eating and no predictable vomitus content.
Vomiting patients in some cases require an extensive workup, but an organized approach will help to minimize the tests necessary for an early diagnosis. If reasonable concern is established, then a minimum data base of CBC, biochemical profile (or specific tests for evaluation of liver, kidney, pancreas, electrolytes), complete urinalysis (pre-treatment urine specific gravity extremely important for diagnosis of renal failure), and fecal examination is essential. Survey abdominal radiographs are frequently performed on vomiting patients and are definitely indicated if thorough abdominal palpation is not possible or suggests an abnormality (e.g., foreign body, pancreatitis, pyometra). Unfortunately these tests are often not done early enough. Even if baseline results are unremarkable they are more than justified because they help to rule out serious problems at the outset (e.g., vomiting due to renal failure, diabetes mellitus, liver disease). Alternatively, any abnormalities provide direction for initial treatment and further diagnostics.
The decision for performing more in-depth diagnostic tests is based on ongoing clinical signs, response to therapy, and initial test results. These tests include ACTH stimulation to confirm hypoadrenocorticism in a patient with an abnormal Na:K ratio or to investigate for this disorder if electrolytes are normal and hypoadrenocorticism is still suspected (note that 10% of dogs with hypoadrenocorticism do not have electrolyte abnormalities), complete barium series or BIPS study (for gastric or intestinal foreign body, gastric hypomotility, gastric outflow obstruction, partial or complete intestinal obstruction; see information in the following paragraphs), cPLI* or fPLI* (canine and feline pancreatic lipase immunoreactivity, respectively, for diagnosis of pancreatitis in dogs and cats), and serum bile acids assay (to assess for significant hepatic disease). Barium swallow with fluoroscopy is often necessary for diagnosis of hiatal hernia disorders and gastroesophageal reflux disease.
BIPS are barium impregnated polyethylene spheres. Traditionally, veterinarians have relied on barium liquid as the contrast agent of choice for gastrointestinal studies. However, recognized limitations of barium liquid have led to the development of barium-impregnated solid radiopaque markers for the diagnosis of motility disorders and bowel obstructions. Barium liquid contrast studies are of limited value in detecting hypomotility. Radiopaque markers can be used to investigate a number of common gastroenteric problems. These spheres have been specifically validated for use in dogs and cats and are the only radiopaque markers with which there is extensive clinical experience in veterinary medicine. BIPS are manufactured in New Zealand and are now available in many countries. Information on availability of this product, including instructions on use and interpretation of radiographic studies, can be found at (www.medid.com).
Use of BIPS represents an excellent means of assessing GI motility in dogs and cats in any practice setting. The very best method for evaluating GI motility is through nuclear scintigraphy. However, nuclear scintigraphy is very limited in availability. A simple way of evaluating motility is to fast a patient for 18 hours, then administer BIPS spheres which have been dispersed in food. After the meal is ingested, abdominal radiographs are made at 6 and 10 hours, at which time all of the spheres should have emptied from the stomach. If they are still retained in the stomach, then subsequent films are made at whatever intervals are convenient for the practice, for example, 18 and 24 hours, in order to determine when all of the BIPS have exited. In normal animals, the stomach will generally be empty after a meal by 7 to 10 hours, or sooner.
One of the most reliable and cost efficient diagnostic tools currently available for evaluation of vomiting is flexible GI endoscopy. Endoscopy allows for direct gastric and duodenal examination, mucosal biopsy from these areas, and in many cases gastric foreign body retrieval (in our hospital, 85% of gastric foreign body cases are managed successfully via endoscopic retrieval of foreign bodies). Endoscopy is considerably more reliable than barium series for diagnosis of gastric erosions, chronic gastritis, gastric neoplasia, and inflammatory bowel disease (a common cause of chronic intermittent vomiting in dogs and cats). It is stressed that biopsy samples should always be obtained from the stomach and whenever possible the small intestine, regardless of gross mucosal appearance. Normal gastric biopsies may support gastric motility abnormalities, psychogenic vomiting, irritable bowel syndrome, or may be noncontributory (i.e., look elsewhere for diagnosis).
Ultrasonography can be useful in the diagnostic work-up of a number of disorders that can cause vomiting. Among the problems that may be detected with ultrasonography are certain disorders of the liver (e.g., inflammatory disease, abscessation, cirrhosis, neoplasia, vascular problems), gall bladder (cholecystitis, choleliths), GI foreign bodies, intestinal and gastric wall thickening, intestinal masses, intussusception, kidney disorders, and others. Needle aspirations and/or biopsies can be done at many sites under ultrasound guidance. However, it is now recognized that liver aspirates are unreliable for establishing a definitive diagnosis of liver disorders other than neoplasia (e.g., lymphoma, mast cell neoplasia), and liver biopsy samples procured via ultrasonography may also be limited in value in some cases, due to small sample size.
Currently, it is recognized that laparoscopy and laparotomy are the best methods for obtaining high quality diagnostic liver samples. The advantage of laparoscopy is that it is minimally invasive, while providing extremely clear views for obtaining liver and other organ samples under direct visualization. Laparoscopy can be performed in any practice setting. Pancreas and kidney biopsies are also routinely obtained via laparoscopy. Abdominal exploratory is indicated for a variety of problems including foreign body removal, intussusception, gastric mucosal hypertrophy syndromes, procurement of biopsies, and for resection of neoplasia.
*cPLI and fPLI are currently available only at Texas A&M University, USA (www.cvm.tamu.edu/gilab).