What exactly is a gastrointestinal ulcer in a dog?

A gastrointestinal ulcer is a break in the mucosal lining that protects the stomach or duodenum (the first segment of the small intestine) from the hydrochloric acid and digestive enzymes the body produces to break down food. The Merck Veterinary Manual describes gastric and duodenal ulcers in dogs as erosions that can range from superficial damage limited to the mucosa to deep, full-thickness perforations that allow stomach contents to leak into the abdominal cavity (Merck Veterinary Manual, 2023). Stomach ulcers are diagnosed more often than duodenal ulcers in dogs, though both share the same underlying mechanism of acid overwhelming a compromised protective barrier.

The mucosal barrier depends on a layer of mucus and bicarbonate secreted by cells lining the stomach wall, along with adequate blood flow to keep those cells healthy and able to regenerate. When something disrupts that barrier — a drug, an underlying illness, or reduced blood supply during shock — acid begins to digest the stomach's own tissue rather than just the food inside it, a process the American College of Veterinary Internal Medicine has described as central to how nonsteroidal anti-inflammatory drug (NSAID) toxicity damages the gut (ACVIM, 2020).

What are the first signs an owner usually notices?

Vomiting is typically the earliest and most consistent sign, and it may include partially digested blood that looks like coffee grounds or, in more severe cases, fresh red blood. Cornell University's Riney Canine Health Center notes that dogs with gastrointestinal ulceration commonly show decreased appetite, lethargy, and abdominal discomfort that owners sometimes mistake for a dog simply being 'off' for a day or two (Cornell Riney Canine Health Center, 2022).

Black, tarry stool — a sign called melena that results from digested blood passing through the intestines — is one of the more specific indicators of an upper GI bleed and warrants same-day veterinary attention rather than a wait-and-see approach. Some dogs also grind their teeth, adopt a hunched 'praying' posture, or show reluctance to lie down flat, all of which reflect the abdominal pain associated with active ulceration (Merck Veterinary Manual, 2023).

What causes stomach ulcers in dogs?

NSAIDs are among the most frequent culprits, and the risk climbs sharply when a dog receives more than one NSAID at once, gets a human formulation like ibuprofen, or is given a veterinary NSAID without a proper washout period after steroids. The FDA has issued warnings specifically about carprofen and other canine NSAIDs causing gastrointestinal ulceration and bleeding when dosing guidelines aren't followed (U.S. Food and Drug Administration, 2021).

Beyond medications, ulcers can stem from liver disease, kidney failure, mast cell tumors that release histamine and stimulate excess acid production, Addison's disease, severe systemic illness causing shock, and foreign body obstructions that damage the intestinal wall. Gastrinomas, rare hormone-secreting tumors, can also drive excessive acid secretion, though they represent an uncommon cause compared with drug-induced and disease-associated ulcers (Merck Veterinary Manual, 2023).

How do veterinarians diagnose a GI ulcer in a dog?

Diagnosis usually starts with bloodwork to check for anemia from chronic blood loss and to screen for underlying organ disease, followed by fecal testing for occult blood when melena isn't obvious on visual exam. Abdominal ultrasound can reveal thickened stomach or intestinal walls, free fluid suggesting perforation, or an underlying mass, and the American Animal Hospital Association lists imaging as a key step in working up dogs with unexplained vomiting or GI bleeding (AAHA, 2022).

Endoscopy remains the gold standard for directly visualizing and, when needed, biopsying an ulcer, since it allows a veterinarian to distinguish a benign erosion from a tumor. Because ulcers frequently occur secondary to another disease, a thorough workup for liver, kidney, and adrenal function is typically part of the diagnostic plan rather than an optional add-on (Cornell Riney Canine Health Center, 2022).

How are gastrointestinal ulcers in dogs treated?

Acid-suppressing medications such as omeprazole or famotidine are the mainstay of treatment, reducing the amount of acid available to further erode the damaged tissue while the mucosa heals; sucralfate is often added as a coating agent that binds directly to ulcerated tissue to protect it during recovery. The Merck Veterinary Manual notes that discontinuing any offending NSAID or other causative drug immediately is essential, since continued exposure prevents healing regardless of medication support (Merck Veterinary Manual, 2023).

Dogs with severe blood loss may need a transfusion, IV fluids for shock, and hospitalization for monitoring, and a perforated ulcer is a surgical emergency requiring immediate repair to prevent life-threatening peritonitis. Treating the underlying cause — whether that means addressing Addison's disease, removing a mast cell tumor, or managing kidney disease — is just as important as the ulcer medications themselves for a lasting recovery.

What can I feed a dog recovering from a stomach ulcer?

Most veterinarians recommend a bland, low-fat, easily digestible diet during recovery, offered in smaller, more frequent meals rather than one or two large ones, since a full stomach can increase acid production and discomfort. Prescription gastrointestinal diets formulated for reduced fat and increased digestibility are commonly used during the healing period and are typically continued for several weeks under veterinary guidance (Cornell Riney Canine Health Center, 2022).

Avoid giving any NSAID, including over-the-counter human products, without explicit veterinary approval, since even a single inappropriate dose can reignite ulceration in a healing stomach. Fresh water should always be available, and any recurrence of vomiting, appetite loss, or dark stool during the recovery period should prompt an immediate recheck rather than waiting out the standard follow-up interval.

Can dogs fully recover from GI ulcers, and will they come back?

Prognosis is generally good for dogs whose ulcers are caught early and whose underlying cause is identified and corrected, with many dogs healing within two to three weeks of starting appropriate acid-suppressive therapy. Dogs whose ulcers stem from an ongoing disease process, such as untreated Addison's disease or a malignant tumor, carry a more guarded outlook until that root cause is controlled (Merck Veterinary Manual, 2023).

Dogs that needed emergency surgery for a perforated ulcer face a higher risk during the immediate postoperative period, but survival rates improve considerably with prompt intervention compared with delayed treatment. Long term, dogs prescribed NSAIDs for chronic conditions like osteoarthritis benefit from periodic veterinary rechecks and the lowest effective dose to minimize the chance of a repeat ulcer.