Gastric Ulceration - Dog

Also known as:

Gastrointestinal ulceration

Description

Is a round or oval punched out lesion of the gastric mucosa ranging from 1-4 cm in diameter.

There are many disease associations including:

Disease type	E.g.
Hypotension	Shock, Sepsis
Drug - induced	Non-steroidal anti-inflammatory drugs (NSAIDs)
Idiopathic	Stress, exercise induced
Inflammatory	Gastritis, Pancreatitis
Neoplastic	Adenocarcinoma, lymphosarcoma, leiomyoma, gastrinoma (Zollinger-Ellison syndrome),
Metabolic/endocrine	Hypoadrenocorticism, liver disease, uraemia, Disseminated Intravascular Coagulation (DIC), mastocytosis and hypergastrinaemia

Gastric ulceration is caused by damage to the gastric mucosa through the above mechanisms. NSAIDs directly damage the mucosa and interfere with the prostaglandin synthesis. Gastric ulceration is worsened by the use of NSAIDs in combination with corticosteroids. This risk can be minimised by using cyclooxygenase-1 (COX-1) sparing NSAIDs.

Gastric acid hypersecretion following mast cell degranulation of histamine and gastrin secretion from gastrinomas is a major cause of gastric ulceration.

Signalment

Sled dogs are prone to gastric ulceration.

Diagnosis

Clinical Signs

History may involve access to toxins and drugs such as NSAIDs. Clinical Signs can include vomiting, haematemesis, malaena, pale mucous membranes, abdominal pain, weakness, inappetance and hypersalivation which can progress to circulatory compromise.

Laboratory Tests

Haematology

Anaemia which may be regenerative initially, and can progress to microcytic, hypochromic and minutely regenerative anaemia. A thrombocytosis may also be present. If a stress leucogram (lymphopenia and neutrophilia) is not present this is supportive of hypoadrenocorticism. Examination of the buffy coat may detect mastocytosis. A Neutrophilia and a left shift are indicative of inflammation or gastric perforation. There may also be abnormalities in haemostasis.

Biochemistry

Increased liver enzymes and bilirubin, decreased urea, albumin and cholesterol will indicate hepatic disease as an underlying problem. If renal disease is present, an azotaemia will be present on biochemistry. If Hypoadrenocorticism is the cause of the ulceration, it is likely biochemistry will show a Sodium:Potassium ratio of less than 27:1. If the animal is vomiting this will lead to electrolyte and acid-base abnormalities, a metabolic alkalosis, hypokalaemia and hypochloraemia.

Urinalysis

Animals will be dehydrated resulting in Hypersthenuria. If renal disease is the underlying cause, urine may be isosthenuric.

Plain radiography

Gastric Ulceration - Copyright David Walker RVC

Not usually diagnostic but can rule out differentials such as foreign bodies and peritonitis.

Positive contrast radiography

May show filling defects.

Ultrasonography

Shows gastric thickening and rules out other differential diagnoses.

Endoscopy and Biopsy

Diagnostic test of choice and allows biopsies to be taken. NSAID related ulcers are reguarly located in the antrum and there is limited mucosal thickening or irregularity whereas ulcerated gastric tumours will have thickened mucosa and edges. Any biopsies should be taken at the edge of normal and diseased tissue to avoid further deepening or perforation.

Treatment

The main aim is to treat any primary underlying cause whilst giving general support. This may be hydrating, restoring electrolytes and acid-base and also helping the gastric lining to recover. Anti-ulcerative therapy should be continued for up to 6-8 weeks.

Fluid Therapy

Depends upon the degree of dehydration, prescence of shock and any other diseases that are affected by volume. Prolonged vomiting or anorexia may lead to hypokalaemia so KCl may need adding to any fluids given. Normal rates for treatment of shock apply with dehydration being overcome by a fluid rate over 24 hours to replace the defecits along with a maintenance rate.

Acid-base correction

Imbalances should be corrected after taking a blood gas reading.

If metabolic acidotic: give sodium bicarbonate but do repeated blood gas
If metabolic alkalosis: replace volume defecit with intravenous NaCl and KCl.
Blocking of acid secretion:

Histamine receptor antagonistsinclude cimetidine, ranitidine and famotidine.

Omeprazole inhibits the hydrogen-potassium ATPase which prevents hydrogen ion production by the parietal cell. This is the drug of choice to treat ulceration associated with mass cell tumours and gastrinomas.

- Gastrin antagonists:
  - proglumide
- Acetylcholine receptor antagonists:
  - atropine
  - pirenzepine
- Adenyl cyclase inhibitors:
  - prostaglangin E2 (PGE) analogues (misoprostol)
- H⁺:K⁺ATPase inhibitors :- for use when patient is refractory to histamine antagonists
  - omeprazole - good for exercise induced gastric ulceration

Mucosal protectants

Such as misoprostol can be given alongside NSAIDs to decrease the risk of ulceration. Sucralfate which is polyaluminium sucrose sulphate, binds to damaged mucosa and assists in the treatment of gastric ulceration. It is best given 2 hours after acid inhibitors to prevent interference.

Prophylaxis

Prophylactic treatment has been shown not to prevent gastric ulceration. Sucralfate is reported to be the best drug in patients receiving high doses of glucocorticoids.

Anti-emetics

Anti-emetics are indicated if vomiting is severe causing fluid and electrolyte imbalances and discomfort.

Analgesia

Is best provided by opiods such as buprenorphine, pethidine and fentanyl.

Antibiotics

Animals suffering from shock and gastric barrier dysfunction may require prophylactic antibiotic cover. First line drugs include ampicillin or a cephalosporin which are effective against Gram-positive, some Gram-negative and some anaerobic bacteria. These can be combined with an aminoglycoside which are effective against Gram-negative aerobes if sepsis is present. Enrofloxacin can also be used instead of an aminoglycoside in skeletally mature animals.

Surgery

May be required to investigate or to resect peforating ulcers which may lead to peritonitis.

Prognosis

For animals with peptic ulcers is good. Prognosis is poorer for patients with renal or hepatic failure related ulcers. It is also poor for animals with gastric carcinoma and gastrinoma.

References

Hall, J.E., Simpson, J.W. and Williams, D.A., (2005) BSAVA Manual of Canine and Feline Gastroenterology (2nd Edition) BSAVA

Merck & Co (2008) The Merck Veterinary Manual

From Pathology Section

Gastric Ulceration - all species

Although ulcers are often secondary to other diseases, primary idiopathic peptic ulcers do occur, due to
- Hyperacidity
- Gastric carcinoma in older dog

Secondary ulcers are often associated with systemic diseases particularly uraemia and mast cell tumours. Gastric ulcer may be the cause of death but is not the primary disease.
1. Mast cell tumours
  - Boxers and Labradors are predisposed to these.
  - Vomit continually together with abdominal pain.
  - Ulcers are usually near the duodenum.
    - Frequently secondarily infected.
    - Often penetrate deeply.
  - Actively secreting mast cell tumours produce histame, leasing to gastric hyperacidity and therefore secondary peptic ulcers.
2. Uraemia
  - Gastric lesions usually occur with chronic renal disease.
    - Gastrin is produced by the G cells of the gastric antrum during the gastric phase of digestion .
      - Acts on H2 receptors on parietal cells to increase production of HCl.
      - Increases release of histamine from gastric mucosal mast cells to increase HCl release.
    - Serum levels of gastrin are increased in chronic renal disease in dogs and cats.
  - In acute renal failure death ensues before gastric ulceration develops.
  - Pathogenesis
    - Loss of nephron and medullary concentration gradient in chronic interstitial nephritis mean collecting ducts cannot resorb fluid.
      - A common cause of interstitial nephritis in the dog was leptospirosis.
    - Consequently, the animal drinks and urinates in enormous quantities, and urea is washed out with large quantities of fluid ("compensated renal failure").
    - If fluid is restricted, urea cannot be washed out and the animal becomes uraemic.
      - Urea is excreted into stomach, giving it a horrible ammoniacal smell and filling it with brown smelly liquid.
      - Urea is also excreted into the colon.
    - Urea in the stomach breaks down to ammonia, irritating the mucosa and contributing to gastric ulcer.
    - Uraemia also causes arteriolar degeneration in the submucosa, leading to hypoxic damage to the mucosa. This is another contributing factor to gastric ulcer.
    - Vomiting causes dehydration and further raises blood urea.
      - A vicious circle is produced- ends in death by vomiting, dehydration and shock.
    - Note: If an animal in compensated renal failure is given anaesthetic, it will not drink much. It then may start to vomit and die due to uraemia.

NSAIDs, Zollinger-Ellison syndrome (due to pancreatic gastrin-secreting tumour), cirrhosis and bile reflux can all also cause gastric ulcers in the dog.