Stomach ulcers in dogs: symptoms, tests and treatment

Overview

An ulcer differs from a superficial erosion in the depth of injury. An erosion is confined to the lining, while an ulcer reaches underlying tissue. Gastroduodenal ulcer means an ulcer of the stomach or duodenum.

Ulceration predominantly affects the stomach and duodenum. Signs cannot establish injury depth. Overall ulcer prevalence in dogs is unknown. Some dogs may have an ulcer without signs. In others, significant bleeding is already the first obvious problem.

Gastritis means inflammation of the stomach lining. With an ulcer, injury extends deeper than this surface layer.

Causes

The lining's protection fails

A thick, bicarbonate-containing mucus layer protects the stomach surface. Tight junctions between cells prevent acidic contents entering tissue. Good local circulation supports replacement of damaged cells. Prostaglandins maintain circulation and increase protective mucus and bicarbonate secretion.

When protection breaks down, stomach acid and digestive enzymes damage tissue. A self-sustaining cycle of inflammation and injury can result. Inflammation may further reduce lining blood flow. It may also reduce protective mucus secretion.

Medicines and underlying diseases

Non-steroidal anti-inflammatory drugs, or NSAIDs, can directly damage the lining. They also reduce protective prostaglandin production. A stomach tumour can ulcerate the lining locally. Mast cell tumours or gastrin-producing tumours may cause excessive acid secretion.

Liver diseases have been associated with stomach and duodenal ulcers. However, a post-mortem study of 168 ulcer or erosion patients found no association with liver disease. The mechanism linking liver disease and ulcers remains uncertain. Other possible causes include foreign body injury, severe inflammation and Addison's disease. The role of Helicobacter bacteria in canine stomach ulcers is unclear. They have been found in 67–100% of studied healthy dogs. Finding the bacteria therefore does not establish that they caused an ulcer.

The independent role of corticosteroids in causing ulcers is disputed. However, glucocorticoid use was associated with ulcers or erosions in the post-mortem study, with an odds ratio of 3.0. This is a statistical association rather than the percentage of all corticosteroid-treated dogs developing disease.

Risk factors

Concurrent NSAID and corticosteroid use increases ulcer risk. Combining different NSAIDs is also avoided. An ulcer can develop even during ordinary veterinary-prescribed NSAID treatment.

No single clear risk breed or general age and sex distribution has been confirmed. In the post-mortem study, working breeds were associated with ulcers or erosions: the odds ratio compared with crossbreeds was 2.8. The significance of breed as an independent risk factor needs further study.

Extreme endurance exercise, such as long-distance sled racing, is a recognised predisposing situation. After a 1,771-kilometre race, 48.5% of examined dogs had stomach ulcers, erosions or bleeding. This describes exceptional race exertion and combined lining changes rather than ulcer risk in ordinary pet dogs.

Typical symptoms

Ulcer signs resemble many other digestive problems.

• Your dog may vomit repeatedly.
• Appetite decreases or meals are left uneaten.
• The abdomen may be tender and your dog seems painful.
• Weight may fall as illness continues.
• Vomit may contain blood or dark coffee-ground material.
• Stools may become black and tarry.
• Severe injury may involve weakness and pallor.

In a study of 82 ulcer patients, 88% had vomiting. Vomiting blood was reported in 32%. Black, tarry stools occurred in 31%. Tiredness was found in 9%. Weight loss was reported in 7%. Absence of visible blood therefore does not exclude an ulcer.

Black, tarry stools develop when blood is partly digested in the gastrointestinal tract. Swallowed blood from the nose can also cause bloody vomit or dark stools.

Complications and consequences

A deep ulcer can bleed and cause anaemia. Prolonged blood loss can cause iron deficiency. Heavy bleeding may require a transfusion. Wall perforation can cause peritonitis and sepsis.

The outlook is more favourable with mild injury and prompt removal of its cause. The outlook for a tumour-related ulcer depends on tumour type and is often poor. Ulceration associated with severe liver failure can be difficult to control. Combined mortality in dogs and cats operated on for intestinal or stomach perforation has been estimated at around 60%. This concerns severely ill surgical patients rather than the outlook for all canine stomach ulcers.

Diagnosis at the vet

Blood counts and bleeding investigations

Your vet reviews every medicine, previous diseases and vomit and stool changes. A blood count assesses anaemia. Platelets and clotting tests help distinguish ulcer bleeding from bleeding due to poisoning or clotting disorders, for example. Blood and urine tests also look for diseases in other organs underlying stomach signs.

Blood urea may rise while creatinine remains normal. Normal urea does not exclude gastrointestinal bleeding. Findings may require liver investigation or adrenal function testing. Faecal occult blood testing can help if bleeding is invisible to the naked eye. However, dietary contents may cause a false positive.

Endoscopy shows the injury

Plain X-rays generally do not show an unperforated ulcer. They may help identify intestinal obstruction or peritonitis. Ultrasound shows possible wall changes, tumours and fluid. Normal ultrasound does not exclude an unperforated ulcer because sensitivity for detecting these is poor. Perforation may reveal free abdominal gas or fluid.

Stomach and duodenal endoscopy is central to confirming an ulcer. Biopsies can also investigate a tumour, for example. Samples are taken at the ulcer edge because sampling its base increases perforation risk. Disease deep within the wall may require a full-thickness surgical sample. A capsule camera may supplement lining assessment.

Capsule imaging found erosions in 10/12 dogs, or 83.3%, receiving long-term NSAIDs. In a comparison group with chronic intestinal signs, stomach erosions occurred in 3/11 dogs. These were lining erosions, so results cannot be interpreted as prevalence of deep or perforated ulcers.

A chronic ulcer can look similar to a stomach tumour. Microscopic tissue examination distinguishes these changes. Repairing granulation tissue and inflammatory cells may surround a chronic ulcer.

Treatment

Removing the cause and reducing acidity

Treatment begins by identifying and correcting the ulcer's cause. An associated NSAID is stopped according to your vet's instructions. Your vet selects medication, aiming to reduce further injury from acidic contents.

Proton pump inhibitors reduce stomach acid secretion more effectively than histamine receptor blockers. Their full acid-suppressing effect develops over around 2–4 days. Combining acid-reducing medicine groups does not improve effectiveness and may reduce the proton pump inhibitor's effect.

Sucralfate binds to damaged lining and may support its protective mechanisms. However, added benefit alongside a proton pump inhibitor has not been demonstrated in canine ulcer treatment. It can impair absorption of other medicines, which is considered in your vet's plan.

Histamine receptor blocker effects may decline with repeated use as tolerance develops. In dogs, this has been found within 13 days and sometimes as early as 3 days. An antacid that temporarily neutralises stomach acidity acts briefly, with little evidence of benefit in ulcer patients. Proton pump inhibitors can also affect how the body processes other medicines.

Stopping prolonged acid suppression is planned because abrupt withdrawal can cause increased acid secretion.

Bleeding and perforation require support

Fluids correct illness-related circulatory and hydration disturbances. Transfusion need depends on bleeding amount, progression of anaemia and clinical condition. It may be needed when tissue oxygen delivery declines. Severe lining damage, shock or sepsis risk may require antibiotics.

A perforated stomach ulcer is treated surgically. Surgery may also be necessary if an ulcer does not resolve medically.

Prevention

Unnecessary combination of NSAIDs increases gastrointestinal adverse effects. Combining them with a corticosteroid further increases ulcer risk. A painkiller prescribed for a person or another animal may harm your dog. Planning considers previous diseases and other medication.

Liver and kidney function are assessed with blood tests when planning long-term NSAIDs. Blood results are also monitored during treatment. Preventive acid medication has not been shown to benefit every dog. It may help in special situations, such as racing sled dogs.

Important for dog owners

Record symptom onset, vomiting frequency, stool colour and food eaten. Bring every medicine's name, amount given and administration times, plus details of possible accidental exposure. A photograph of vomit or stools may help show the change. Agree feeding and follow-up according to your dog's condition and procedures performed.

If vomiting, bloody or black stools, or poor appetite develops during NSAID treatment, stop the medicine and contact your vet. This concerns suspected NSAID adverse effects; do not change other long-term medicines yourself. At discharge, confirm what to do if food or prescribed medication will not stay down.

Frequently asked questions

Is a stomach ulcer the same as gastritis?

Gastritis means inflammation of the stomach lining. An ulcer extends through the lining into deeper wall layers. A superficial erosion remains confined to the lining. Vomiting or abdominal pain cannot establish injury depth, and many other stomach diseases cause the same signs.

Can a dog have an ulcer without vomiting blood?

An ulcer may occur without visible blood in vomit or stools. Some dogs have no signs at all. Absence of blood alone therefore does not determine investigation need: vomiting, pain, appetite and previous medication also matter.

Can an ordinary canine painkiller cause an ulcer?

An NSAID-related ulcer or perforation can develop even during ordinary treatment intended for animals. Risk increases when different NSAIDs are combined or a corticosteroid is given alongside them. Report vomiting, black stools or appetite changes to your vet.

Can ultrasound detect a stomach ulcer?

Ultrasound can find wall changes or an ulcer, but detection of unperforated ulcers is unreliable. Endoscopy directly shows the lining and allows biopsies. Endoscopy may therefore be needed after normal ultrasound if signs and other findings maintain strong suspicion.

Does a stomach ulcer always need surgery?

An unperforated ulcer can be managed by treating its cause and reducing acidity. A perforated ulcer needs surgery. An ulcer unresponsive to medical treatment may also require surgery. Transfusion and fluids may be needed beforehand to stabilise your dog.