• Use of positive, negative or a combination of contrast agents to highlight the gastric lumen.

Uses

• Identification of the position of the stomach, eg in ascites or if suspect gastric displacement, eg diaphragmatic hernia Diaphragm: traumatic hernia.
• Investigation:
  • Vomiting Vomiting or hematemesis.
  • Melena.
  • Suspected radiolucent foreign bodies Stomach: foreign body.
  • Abdominal pain or distension.
  • Inappetance.
• Assessment of lumen size and gastric axis if stomach not visible on plain films.

Advantages

• Relatively simple procedure in most patients.
• Non-invasive.

Disadvantages

• Often difficult to assess subtle mucosal lesions.
• Not very accurate for assessment of motility disorders.

Technical problems

• Difficult to interpret if not familiar with normal appearance.

Alternative techniques

• Gastric ultrasonography (should precede contrast radiography if performed on same day).
• Gastroscopy Gastroscopy (should precede contrast radiography if performed on same day,although drugs used for restraint will affect gastric motility).
• Scintigraphy.
• Barium impregnated polyurethane spheres (BIPs).

Time required

Preparation

• Dependent upon method of restraint.
• Food withheld for 12-24 hours (may not be required if animal is inappetant).
• Enemas required ideally night before but not within 2-3 hours of procedure.
• May need to withhold food for 24 hours if delayed gastric emptying.
• If considering endoscopy Gastroscopy this should be performed before contrast radiography.

Decision taking

Criteria for choosing test

• Is the examination appropriate?
• Can you make the diagnosis without it?
• Will your management of the case be affected by the outcome of the examination?

Risk assessment

• If suspect gastrointestinal tract rupture it is theoretically safer to use water-soluble contrast agents:
  • Gastrointestinal tract rupture requires surgical intervention and abdominal lavage so leakage of contrast agents may not be a particular problem and iodine-based agents may exacerbate hypovolemia in a shocked animal by drawing fluid into the GI tract.