Consequences of Gastric Disease - Pathology

Vomiting

• Has potentially lethal effects in the monogastric animal.

Water Loss

• Fluid loss is evident as:
  1. An increased PCV or haematocrit.
  2. An increased total protein concentration.
  3. A prerenal azotaemia.

Gastric Electrolyte Loss

• The main losses are of H⁺ and Cl^-, and also K⁺
• Can potentially cause metabolic alkalosis, although this is only likely with disease which stops at the pylorus, e.g.: pyloric outflow obstruction.
  • In cases where mild alkalosis occurs, homeostatic mechanisms produce a more alkaline urine to restore normal body pH.
  • However, in severe metablolic alkalosis with marked dehydration, acidic urine may be produced- this is termed paradoxical aciduria.
    • Because vomiting induceses hypokalaemia, there is an overriding stimulus in the kidney for Na⁺ (and therefore water) retention.
    • Na+ can only be resorbed in exchange for H+
      • H⁺ is therefore excreted in the urine, causing it to be acidic.
    • Vomiting also induces hypochloraemia, meaning bicarbonate rather than chloride is resorbed with the Na+ to maintain electrical neutrality
      • This perpetuates the alkalosis.
• Vomiting does not occur in the ruminant although abomasal content may reflux into the forestomachs.
  • Sequestration of secretions in the abomasum will have similar effects to pyloric outflow obstruction with vomiting in the monogastric animal.
    • e.g. abomasal torsion
    • Causes dehydration, hypochloraemia, hypokalaemia and metabolic alkalosis.

• Lesions in the small intestine can also lead to vomiting
  • Both gastric acid and pancreatic and intestinal bicarbonate secretions are lost
    • Animal consequently has a normal pH or may even be acidotic.

Raised Intraluminal pH

• Associated with some forms of gastritis.
  • e.g. Ostertagiasis
• Causes failure of digestion.
  • Anorexia and weight loss follow.
• Increases the number of bacteria in the stomach.
• Diarrhoea reults
  • Cause is unknwn is unknown but appears to be related to the elevated pH.

Hyperacidity

• May develop in certain gastric disturbances
• Thought to be a contributory factor in peptic ulceration.

Anaemia

• May also develop in certain gastric diseases
• Is usually haemorrhagic in nature
  • Due to bleeding from gastric ulceration.