Diagnostic approach to vomiting (Proceedings)

Vomiting is among the most common clinical signs in companion animals. Although a protective mechanism associated with removal of noxious ingested substances, it is also associated with many diseases. Due to the multitude of causes it can be a challenge for veterinarians to diagnose and manage vomiting. Vomiting is not a diagnosis but is a clinical sign of any number of disorders including gastrointestinal disorders, systemic or metabolic disorders and toxicities. Sudden onset vomiting or chronic, intermittent vomiting causes significant concern for pet owners. Left untreated, vomiting can cause serious complications such as volume depletion, acid-base disturbances, esophagitis, and malnutrition or malabsorption and/or aspiration pneumonia.

Although the presentation of vomiting may not signify a serious disorder – it is often the first clinical sign in toxin ingestion, pancreatitis, renal failure, Addisonian crisis, parvovirus infection, and intestinal obstruction. A thorough evaluation must be performed to arrive at an accurate, timely diagnosis. It is also of paramount importance that the clinician questions the owner about potential toxin ingestion (ethylene glycol, medication ingestion, chocolate or xylitol) or other pertinent history.

It is essential to differentiate between vomiting and regurgitation at the outset. Regurgitation is defined as passive, retrograde movement of ingested material. It usually happens right after ingestion before the ingesta reaches the stomach, although it can be delayed hours. Vomiting is defined as a forceful rejection of gastric and sometimes proximal small intestinal contents via the oral cavity. Vomiting involves three stages: nausea (depression, salivation, lip-licking frequent swallowing and sometimes vocalization), retching, and expulsion. The history can be helpful to confirm the patient is vomiting and the signs are not associated with coughing, gagging, dysphagia or regurgitation, which are very confusing to the owner. In some cases the distinction is difficult to differentiate based on history alone.

Once you have determined vomiting is present, a complete historical review with emphasis on all body systems is imperative to develop an effective diagnostic plan. For example patient signalment may indicate a young, unvaccinated animal that is more susceptible to infectious disease, such as distemper or parvovirus. Consider the following 1) duration of signs, 2) frequency of signs (acute? chronic? intermittent?), 3) appearance of the vomit (projectile?), 4) association with drinking or eating, 5) signalment and past pertinent history and treatments, 6) diet and environment, 7) review of systems, (PU/PD? coughing? sneezing? diarrhea?), 8) content of the vomitus (food? bile? blood?).

A thorough dietary history, including type of diet, recent diet change, feeding of table scraps, free-roaming behavior allowing ingestion of garbage or foreign objects or toxins (including house plants or nsaids) is very important. Vomiting in the immediate post-prandial period may suggest an adverse reaction or intolerance to food or simply over eating. Vomiting a partially digested or undigested meal after six to eight hours of eating indicates a gastric outflow obstruction (caused by foreign bodies, polyps, mucosal hypertrophy and or tumors.). Vomiting bile-tinged fluid in the morning often results from bilious vomiting syndrome or reflux gastritis. Bright red blood or digested blood in the vomitus indicates gastrointestinal erosion or ulcer. The history may identify the use of medications, such as nsaids, which can cause gastritis or ulceration. The presence of additional concurrent signs, such as diarrhea, may help to order the rule-out list.

A complete physical exam can be normal or demonstrate other symptoms and therefore provide additional information. If vomiting is more constant, signs of dehydration may be present including delayed capillary refill time, decreased skin turgor, enophthalmos, pale mucous membranes, tachycardia and cold extremities. The abdomen should be carefully palpated to check for masses, foreign bodies, dilated loops of bowel, intussusceptions, effusion or organomegaly. A rectal examination provides characteristics of colonic mucosa and feces character. Patients with colitis or severe constipation often vomit. Foreign material in the feces infers foreign body ingestion. Melena is suggestive of bleeding in the upper gastrointestinal tract. Polyuria, polydipsia, polyphagia, pale mucus membranes, bradycardia or tachycardia, hepatomegaly or splenomegaly, small irregular kidneys, ascites, and icterus are all signs suggestive of systemic disease.

The history and physical examination findings should guide the clinician to the next step in the work-up if a diagnosis is not found. Because most cases of acute vomiting are due to dietary indiscretion, few diagnostics are required and response to symptomatic therapy by correcting the indiscretion or instituting a bland, highly digestible diet for a period of time resolves the vomiting and confirms the diagnosis.

In severe or chronic cases laboratory diagnostics are indicated and the minimum database should include a complete blood cell count, biochemical profile, urinalysis and T4 depending on age. Additionally, a fecal examination (fecal centrifugation assay and Giardia ELISA) for parasites and survey abdominal radiographs (if foreign body is suspected or thorough abdominal palpation is not possible) are appropriate. This basic assessment is required to exclude all non-gastrointestinal causes of vomiting. Normal baseline results are justified because they rule out serious problems at the beginning. Alternatively, any identified abnormalities provide direction for initial treatment and further diagnostics.

If no abnormalities are identified, animals with mild disease are usually treated symptomatically first. If they fail to resolve with symptomatic therapy or have severe disease, then an in-depth diagnostic work-up is in order. This diagnostic work-up depends on what is available in your practice but can include abdominal ultrasound examination, contrast studies, and endoscopy.

Before more invasive testing is commenced, animals with mild signs should go through a dietary food trial and receive treatment for gastrointestinal parasites. These treatments are very applicable to these mildly classified cases. Adverse food reactions consist of food intolerances or food allergies. Pet owners mostly always misunderstand this difference. Food intolerance is a non-allergic food hypersensitivity or gastrointestinal response that is a delayed, negative reaction to a food or food additive, such as a preservative. Food intolerances can result from the absence of specific chemicals or enzymes needed to digest a food substance. A true food allergy is an immune system response mediated against a protein requiring the presence of IgE antibodies. Although both can result in vomiting and variable inflammatory responses, it is important to understand the difference between the two. (Most common allergens are beef, dairy, and wheat. Less common but still documented are lamb, chicken, egg and soy.)

Dietary food intolerances are probably the most common cause of chronic, intermittent vomiting. These animals appear healthy and intermittently vomit food shortly after ingestion. In these cases, removal of the causative factor regularly results in quick improvement. Animals suspected of having food intolerances should be placed on a hypoallergenic diet for a minimum of 2 weeks. Patients with suspected food allergies require prolonged dietary trials to demonstrate a response. Since the allergens differ patient to patient, there is no universal ideal diet; therefore various dietary trials may be necessary. When the patient is diet responsive then the diagnosis of food allergy is supported.

In animals that chronically vomit with little signs of debilitation the clinician must consider parasites. Proper fecal examination techniques usually diagnose whipworms, ascarids and Giardia sp. Considered uncommon, Physaloptera spp. eggs do not readily float with fecal examination and therefore their prevalence may be underestimated. Diagnosis is frequently made with endoscopic exam. In chronic vomiting cases, symptomatic anthelmintic therapy is warranted. The author usually prescribes fenbendazole at 50 mg/kg PO daily for three to five days.

Patients that fail to improve with adequate dietary and/or anthelmintic therapy and persistently vomit or lose weight are recommended to undergo a more in-depth gastrointestinal evaluation. Diagnostic techniques for the proximal gastrointestinal tract include laboratory evaluation, radiology, ultrasonography, endoscopy or surgery.

Additional laboratory diagnostics to consider include thyroid testing, corticotropin stimulation for hypoadrenocorticism, pancreatic lipase immunoreactivity to aid the diagnosis of pancreatitis, serologic screening for leptospirosis, especially in patients with liver or renal abnormalities, serum bile acid assay in patients with hepatic disease, fecal ELISA testing for parvovirus especially in young or unvaccinated animals. Serum gastrin levels can be indicated if a gastrinoma, i.e. Zollinger-Ellison syndrome, is suspected.

If survey abdominal radiographs are normal, a complete barium series is indicated. Advantages of contrast radiography versus more invasive diagnostics such as endoscopy or exploratory/laparoscopy include: readily available in most practices, non-invasive, does not require general anesthesia, visualizes the duodenum, evaluates gastric position and size, provides visual description of gastric motility and emptying, and detects extraluminal and submucosal masses. A barium series is time consuming to perform, costly to the client, and is an extra source of radiation to the staff. When lesions are identified a tissue sample must be obtained. When a foreign body is identified – it must be removed via endoscopy or laparotomy. A barium swallow with fluoroscopy is often necessary for diagnosis of hiatal hernia disorders and gastroesophageal reflux disease.

Abdominal ultrasonography can be useful in the non-invasive, diagnostic work-up of many disorders causing vomiting. Detectable problems include disorders of the liver (e.g. inflammatory disease, abscesses, cirrhosis, neoplasia and vascular problems), gastrointestinal foreign bodies, gall bladder problems (cholecystitis, choleliths), pancreas problems (pancreatitis, cysts, neoplasia) gastric and intestinal wall thickening, intestinal masses, and intussusceptions. An ultrasound guided fine needle aspirate or true-cut biopsy may be preformed.

A reliable and mostly cost-efficient diagnostic tool currently available for evaluation of chronic vomiting is flexible gastrointestinal endoscopy. Endoscopy offers the best means of directly examining the gastric and duodenal mucosal surfaces, lumen and obtaining mucosal biopsies and mucosal brush cytology. It cannot be stressed enough that when performing endoscopy, always obtain gastric and duodenal biopsies, even if the mucosa looks normal because normal gastric biopsy may support gastric motility disorder. Check a urea culture for Helicobacter spp.

If endoscopy is unavailable, then exploratory abdominal surgery and full thickness biopsies may be indicated. The surgeon should evaluate the entire abdomen noting each organ. Full-thickness biopsies should be collected from the stomach, duodenum, ileum, jejunum, pancreas, liver, and lymph nodes.

References available on request