A dog that vomits once after eating grass is unremarkable. A dog that vomits weekly, or daily, or in cycles that come and go for weeks or months, has a problem that deserves a structured diagnostic approach — not just an anti-nausea injection and a "come back if it happens again."

Chronic vomiting is one of the most common reasons dogs are presented to a veterinarian, and one of the most frustrating for owners who have been told to "wait and see" or have tried multiple diet changes without a clear diagnosis. This article explains what chronic vomiting actually means, how veterinarians work it up, what conditions the workup is trying to rule in or out, and what the 2026 ACVIM consensus on canine chronic inflammatory enteropathy (CIE) now recommends.

Quick answer

Chronic vomiting in dogs is generally defined as vomiting that persists for three weeks or longer, or that recurs in episodes over a longer period. It is not a diagnosis — it is a clinical sign with many possible causes, ranging from simple dietary intolerance to inflammatory bowel disease (IBD), intestinal lymphoma, liver disease, kidney disease, pancreatitis, or systemic illness.

The diagnostic workup proceeds in steps: baseline bloodwork (CBC, chemistry, urinalysis), fecal testing and empiric deworming, then — if those do not identify a cause — a structured food trial with a hydrolyzed-protein or novel-protein diet for a minimum of two weeks (the 2026 ACVIM consensus recommends at least 14 days to assess dietary response). If the vomiting persists despite a strict diet trial, additional testing includes a GI panel (cobalamin, folate, pancreatic lipase), resting cortisol to screen for hypoadrenocorticism, abdominal ultrasound, and ultimately endoscopy or surgical biopsy.

Biopsy is the only way to definitively diagnose inflammatory bowel disease and to distinguish it from intestinal lymphoma. However, biopsy is not the first step — it is reserved for dogs that fail dietary and medical trials, or for those with severe signs (weight loss, protein-losing enteropathy, hypoalbuminemia) that require a tissue diagnosis to guide immunosuppressive treatment.

When is vomiting "chronic"

Not all vomiting requires an extensive workup. The following patterns help distinguish chronic, clinically significant vomiting from acute, self-limiting, or episodic benign vomiting:

The 2026 ACVIM consensus on canine chronic inflammatory enteropathy (CIE) uses the term "chronic" for clinical signs persisting beyond 14–21 days. Chronic inflammatory enteropathy encompasses food-responsive enteropathy (FRE), antibiotic-responsive enteropathy (ARE), and steroid- or immunosuppressive-responsive enteropathy (SRE/IRE). The diagnostic pathway is designed to identify which subtype is present, because treatment differs substantially.

What causes chronic vomiting in dogs

Chronic vomiting arises from gastrointestinal (GI) causes and non-GI (extra-intestinal) causes. The workup is designed to separate these efficiently.

GI causes

• Chronic inflammatory enteropathy (CIE) / inflammatory bowel disease (IBD): the most common cause of chronic vomiting and diarrhea in dogs. A complex, immune-mediated inflammation of the gastrointestinal tract influenced by genetics, diet, gut microbiome, and environmental factors. Breeds with known predisposition include German Shepherd Dogs, Soft-Coated Wheaten Terriers, Chinese Shar-Peis, Boxers, and French Bulldogs — but any breed can be affected.
• Dietary intolerance or adverse food reaction: a subset of CIE that responds to dietary change alone (food-responsive enteropathy). This is more common than many owners realize and is often the first condition the workup tests for.
• Intestinal parasites: Giardia, hookworms, roundworms, whipworms, and Strongyloides can all cause chronic GI signs. Fecal testing may miss intermittent shedders, which is why empiric broad-spectrum deworming with fenbendazole is recommended as an early step.
• Partial GI obstruction: chronic or intermittent vomiting caused by a foreign body, intussusception, or stricture that does not fully block the intestine but disrupts normal motility.
• GI neoplasia: intestinal lymphoma, adenocarcinoma, leiomyosarcoma, and mast cell tumors can present with chronic vomiting, often with weight loss and sometimes with a palpable abdominal mass.
• Helicobacter infection: Helicobacter species are found in the stomachs of many healthy dogs, but in some cases they may contribute to chronic gastritis.
• Gastric motility disorders: delayed gastric emptying without mechanical obstruction.

Extra-intestinal causes

• Chronic kidney disease: uremic gastritis from toxin accumulation.
• Liver disease: hepatitis, hepatic lipidosis, portosystemic shunts.
• Pancreatitis: chronic or recurrent pancreatitis can present with intermittent vomiting.
• Hypoadrenocorticism (Addison's disease): an important and easily missed cause of waxing and waning GI signs. A resting cortisol screen is recommended in the workup of any dog with unexplained chronic GI disease.
• Hyperthyroidism: rare in dogs but possible with thyroid carcinoma.
• Toxin exposure: chronic low-level exposure to irritants or medications (NSAIDs, corticosteroids).

Step-by-step diagnostic workup

The workup is intentionally sequential. Each step either identifies a cause or narrows the differential list before committing to more invasive and expensive testing.

Step 1: History, physical exam, and minimum database

The foundation of the workup is a detailed history and physical examination. Key history questions:

• Frequency, timing, and appearance of vomitus (food, bile, blood, foam).
• Relationship to meals (immediately after vs. hours later).
• Concurrent signs: diarrhea, weight loss, appetite changes, energy level, stool quality.
• Diet history: current food, recent changes, treats, table food, access to garbage or outdoor foraging.
• Medication history: NSAIDs, steroids, antibiotics, supplements.
• Environment: multi-pet household, travel history, exposure to toxins or standing water.

The minimum database includes:

• CBC (complete blood count): evaluates for anemia (GI blood loss, chronic disease), leukocytosis (inflammation, infection), eosinophilia (parasites, eosinophilic gastroenteritis), and thrombocytopenia.
• Serum chemistry panel: evaluates kidney function (BUN, creatinine, SDMA), liver enzymes (ALT, ALP, GGT), total protein and albumin (hypoproteinemia is a red flag for protein-losing enteropathy), electrolytes (hypokalemia from chronic vomiting), glucose, and cholesterol.
• Urinalysis: helps interpret kidney function, assess hydration, and screen for concurrent urinary disease.

Step 2: Fecal testing and empiric deworming

Fecal flotation and antigen testing (Giardia ELISA) are standard. However, because parasite shedding can be intermittent, the ACVIM consensus and most internists recommend empiric deworming with fenbendazole (50 mg/kg once daily for 5 consecutive days) regardless of fecal test results. This treats Giardia, hookworms, roundworms, whipworms, and Strongyloides.

Step 3: Diet trial

If the minimum database and fecal testing do not identify a cause, the next step is a structured food trial — not just switching brands, but a controlled diagnostic intervention.

The 2026 ACVIM consensus on CIE recommends a diet-first approach as the initial therapeutic trial:

• Hydrolyzed protein diet: proteins broken into small peptides that are less likely to trigger an immune response. Examples include prescription hydrolyzed diets from Royal Canin, Hill's, and Purina.
• Alternatively, a novel protein diet: a single protein and carbohydrate source the dog has not previously eaten. Less reliable than hydrolyzed diets because many over-the-counter "novel" proteins are cross-contaminated during manufacturing.
• Duration: minimum 14 days to assess initial response, but many internists recommend extending to 4–6 weeks for a full assessment. The ACVIM consensus notes that food-responsive enteropathy is the most common CIE subtype and often responds within the first two weeks.
• Strict compliance: no treats, table food, flavored medications, access to other pets' food, or outdoor scavenging. Even small dietary infractions can invalidate the trial.

If the vomiting resolves or significantly improves during the diet trial, the diagnosis is food-responsive enteropathy — a subset of CIE — and long-term dietary management becomes the primary treatment.

Step 4: GI panel and endocrine screening

If the diet trial fails (vomiting persists despite strict compliance), the next step is advanced laboratory testing:

• GI panel: serum cobalamin (vitamin B12), folate, and pancreatic lipase (SPEC cPLI or equivalent). Low cobalamin indicates ileal disease or small-intestinal bacterial overgrowth (SIBO) and has prognostic significance — dogs with hypocobalaminemia have a worse response to treatment and require B12 supplementation. Low folate suggests proximal small-intestinal disease or SIBO.
• Resting cortisol: a single baseline cortisol measurement. If the result is above 2 µg/dL, hypoadrenocorticism (Addison's disease) is effectively excluded. If it is below 2 µg/dL, an ACTH stimulation test is needed. Addison's disease is an important mimic of chronic GI disease and is fatal if missed.
• Total T4: to screen for hypothyroidism, which can contribute to GI signs, although it is a less common cause of isolated chronic vomiting.
• Canine CRP (C-reactive protein): an inflammatory marker that can help assess disease severity and monitor treatment response, though it is not specific for GI disease.

Step 5: Abdominal ultrasound

Abdominal ultrasound evaluates the gastrointestinal tract wall (thickness, layering, masses, lymph nodes), liver, pancreas, spleen, kidneys, and other abdominal organs. It is not a replacement for biopsy — a normal ultrasound does not rule out IBD or early neoplasia — but it serves several important purposes:

• Rules out structural disease: masses, foreign bodies, intussusception, obstructive lesions, and major organ disease.
• Assesses GI wall changes: thickening, loss of normal layering (suspicious for neoplasia, especially lymphoma), muscularis hypertrophy, and mesenteric lymph node enlargement.
• Guides sampling: ultrasound-guided fine-needle aspirates of masses, enlarged lymph nodes, or abnormal organs.
• Assesses disease severity: helps determine whether the case can continue to be managed in general practice or should be referred to an internist.

The ACVIM consensus recommends abdominal ultrasound before biopsy to rule out structural disease and to help plan the biopsy approach (endoscopic vs. surgical).

Step 6: Biopsy — endoscopy or exploratory surgery

Biopsy is the gold standard for diagnosing IBD and distinguishing it from intestinal lymphoma, which cannot be reliably differentiated on imaging alone. The 2026 ACVIM consensus emphasizes that histopathology — not response to empiric treatment — is required for a definitive diagnosis.

Endoscopic biopsy is less invasive and requires shorter recovery. It allows direct visualization of the stomach and duodenum (upper endoscopy) or colon and ileum (lower endoscopy), and targeted sampling of abnormal mucosa. Limitations include reach — endoscopy cannot access the jejunum or deeper intestinal layers — and sample quality, which depends on technique and the number of biopsies obtained.

Surgical (exploratory) biopsy provides full-thickness samples from any segment of the GI tract, as well as access to the liver, pancreas, and lymph nodes that are beyond endoscopic reach. It is more invasive, carries higher risk (dehiscence, especially in hypoalbuminemic patients), and requires a longer recovery, but it provides the most comprehensive diagnostic information.

The choice between endoscopic and surgical biopsy depends on the suspected disease location, the patient's stability, the practice's capabilities, and whether referral to a specialist is available. In most cases, endoscopy is the first approach; surgery is reserved for cases where endoscopy is nondiagnostic, where full-thickness samples are needed, or where surgical correction of a lesion is anticipated.

What the 2026 ACVIM CIE consensus changes

Published in January 2026 in the Journal of Veterinary Internal Medicine (Heilmann, Jergens, Kathrani, Allenspach, et al.), this is the first major update to the CIE guidelines in over a decade. Key takeaways for primary-care veterinarians and pet owners:

1. Diet-first approach: the consensus strongly recommends a structured dietary trial as the initial diagnostic-therapeutic intervention, before antibiotics or immunosuppressive drugs.
2. Antibiotic use is de-emphasized: antibiotic-responsive enteropathy is still recognized, but the consensus discourages empiric antibiotic use before dietary trials are completed. This reflects growing concern about antimicrobial resistance and microbiome disruption.
3. Probiotics: the De Simone Formulation (used in Visbiome Vet) is the only probiotic identified as having RCT-level evidence supporting its use as an adjunct in CIE, after diet trials.
4. CIBDAI scoring: the Canine Inflammatory Bowel Disease Activity Index (CIBDAI) — which scores attitude/activity, appetite, vomiting, stool consistency, stool frequency, and weight loss on a 0–18 scale — is recommended for initial assessment and treatment monitoring.
5. Two-tier diagnostic approach: the consensus recommends classifying patients as CIE-I (mild to moderate disease, amenable to stepwise outpatient workup) or CIE-II (severe disease with weight loss, hypoalbuminemia, or protein-losing enteropathy, requiring more aggressive and often specialist-led workup).

When to refer to an internist

Referral to a board-certified small-animal internist is appropriate when:

• The dog has weight loss, hypoalbuminemia (albumin below 2.0 g/dL), or clinical signs suggestive of protein-losing enteropathy.
• The vomiting is progressing despite appropriate dietary and medical management.
• Abdominal ultrasound reveals findings concerning for neoplasia, severe layer disruption, or significant lymphadenopathy.
• Endoscopy or surgical biopsy is needed and not available in your practice.
• The owner wants a definitive diagnosis (histopathology) before committing to long-term immunosuppressive therapy.
• The dog has concurrent disease (hepatopathy, pancreatitis, hypoadrenocorticism) complicating the clinical picture.

Early referral does not mean you failed as a primary-care veterinarian. It means you recognized a case that will benefit from the additional tools, experience, and perspective of a specialist.

What owners should ask their veterinarian

If your dog has been vomiting chronically and you are unsure whether the workup has been thorough enough, these are productive questions to raise:

• "Have we done baseline bloodwork, urinalysis, and fecal testing?"
• "Has my dog been dewormed with fenbendazole even if the fecal test was negative?"
• "Should we try a strict hydrolyzed-protein diet trial for at least two weeks before doing more invasive tests?"
• "Do we need to check cortisol levels to rule out Addison's disease?"
• "Should we check vitamin B12 (cobalamin) levels?"
• "Would an abdominal ultrasound help rule out structural problems before we consider biopsy?"
• "At what point should we consider referral to an internal medicine specialist?"

Sources

• Heilmann RM, Jergens AE, Kathrani A, Allenspach K, Gaschen F, et al. ACVIM-endorsed statement: consensus statement and systematic review on guidelines for the diagnosis and treatment of chronic inflammatory enteropathy in dogs. J Vet Intern Med. 2026;40(1):aalaf017. https://pubmed.ncbi.nlm.nih.gov/41742497
• dvm360. ACVIM endorses updated guidance on canine chronic inflammatory enteropathy. February 25, 2026. https://www.dvm360.com/view/acvim-endorses-updated-guidance-on-canine-chronic-inflammatory-enteropathy
• dvm360. Diagnosis and management of acute and chronic vomiting in dogs and cats (Proceedings). https://www.dvm360.com/view/diagnosis-and-management-acute-and-chronic-vomiting-dogs-and-cats-proceedings
• Cornell University College of Veterinary Medicine. Inflammatory bowel disease (IBD). https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-topics/inflammatory-bowel-disease-ibd
• Davies Veterinary Specialists. Inflammatory bowel disease fact sheet. https://www.vetspecialists.co.uk/fact-sheets-post/inflammatory-bowel-disease-fact-sheet
• Veterinary Information Network (VIN). Veterinary Partner — Inflammatory bowel disease in dogs and cats. https://veterinarypartner.vin.com/doc?id=4951476&pid=19239
• Vet-CT. Managing chronic vomiting and diarrhoea in dogs. https://resources.vet-ct.com/managing-chronic-vomiting-and-diarrhoea-in-dogs
• dvm360. Diagnosis and management of IBD in dogs and cats. https://www.dvm360.com/view/diagnosis-and-management-of-ibd-in-dogs-and-cats