Contributors: Barbara J Watrous

 Species: Feline   |   Classification: Techniques

Introduction Requirements Preparation Procedure Aftercare Outcomes Further Reading

Introduction

  • 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: hernia.
  • Investigation of vomiting Vomiting or hematemesis.
  • Investigation of melena.
  • Identification of suspected radiolucent foreign bodies Stomach: gastric foreign body.
  • Investigation of abdominal pain or distension.
  • Investigation of inappetence.
  • 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

  • Dependant upon method of restraint.
  • Food witheld for 12-24 hours (may not be required if animal 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 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.

Requirements

Materials Required

Minimum equipment

  • X-ray machine.
  • Cassette.
  • Processing facilities.
  • Protective clothing (lead apron) for radiographer.
  • Positioning aids (sandbags, cradle and ties).
  • Method of labeling film.
  • Large syringe.
  • Means of keeping mouth open for stomach tubing, eg inner part of bandage roll.
  • Stomach tube.

Ideal equipment

  • Ability to process films during procedure so that repeat radiographs can be taken during course of study if required.
  • High output x-ray machine.
  • High definition screen.
  • Mouth gag.

Minimum consumables

  • Radiographic film.
  • Contrast agent.
  • Water-soluble lubricant for stomach tubing.

Preparation

Dietary Preparation

  • Withhold food 12-24 hours prior to procedure.

Restraint

  • Sedation.
  • Low dose of acepromazine Acepromazine maleate (0.05-0.1 mg/kg) has minimal effect on gastrointestinal motility and transit times.
    Avoid diazepam Diazepam, xylaxine Xylazine, barbituates, opoids and parasympathic drugs, (eg atropine) Atropine, as they have been shown to delay gastric emptying in cats.
  • If performing negative or double contrast studies gastric motility can not be assessed so effect of sedation is unimportant.

Other Preparation

  • Administer cleansing enema Enema the night before procedure and 2-3 hours before procedure if necessary.
  • Glucagon has been used to promote gastric relaxation for double-contrast gastrography, but is very expensive.

Procedure

Approach

Step 1 - Control films

  • Plain abdominal radiographs Radiography: abdomen should be obtained prior to contrast study to:
    • Check exposure settings and processing.
    • Confirm animal adequately prepared, ie colon empty.
    • Confirm positioning adequate.
    • Confirm diagnosis not apparent without contrast study.
    • Identify radiopaque foreign bodies which may be masked by barium.
  • Premeasure stomach tube against animal from mouth to stomach, and mark on tube length required to reach stomach.

Step 2 - Selection of contrast agent

  • Positive:
    • Liquid barium (10 ml/kg,15% W/W).
    • Iodine-based contrast (2.2 ml/kg, 10% W/W) (hyperosmolar and may cause hypovolemia and shock. Expensive).
    • Suitable for assessing position of stomach, wall thickness and gastric emptying.
    • May mask foreign bodies.
    • Can be used for follow through investigation of small intestine.
  • Negative:
    • Air (4-8 ml/kg).
    • Carbon dioxide/air.
    • Suitable for assessing position of stomach and identifying foreign bodies and gross wall thickening.
  • Double contrastwhich provides best information on mucosal detail.

Step 3 - Insert stomach tube

  • Insert premeasured length of stomach tube Stomach tubing to level of stomach.
  • Inject small amount of water/saline to ensure tube correctly placed in stomach and not respiratory tract.

Core Procedure

Step 1 - Instill contrast agent

  • Inject (negative or positive) contrast in sufficient quantity to distend stomach Stomach: normal - gastrogram lateral   Stomach: normal - gastrogram VD .
    Tendency to underfill stomach in most cases.
  • In cats that are continuously vomiting give low dose of barium (20 ml) orally - this may reduce gastric irritation and permit radiography.

Double contrast gastrography

  • Administer 1-3 ml/kg of barium by nasogastric tube Nasoesophageal intubation.
  • Roll animal through 360degrees then re-stomach tube and inflate stomach with air/carbon dioxide 5-10 ml/kg.
  • Glucagon may be given prior to administration to allow maximum distension of stomach.

Step 2 - Obtain radiographic views

  • Withdraw stomach tube before radiography.
  • See abdominal radiography Radiography: abdomen for details of positioning.
  • Immediately take DV, VD, left and right lateral projections.
  • Repeat after 5-10 min.
  • If abnormality seen make sure it is consistent on several films/views.
  • If barium alone has been used a follow through study of intestines can be performed.
    This is not possible if negative or double contrast study performed.

Exit

Step 1 - Assess radiographs

  • Ensure stomach adequately distended for interpretation.
  • Stomach contractions may mimic pathology, including mural thickening and stenosis - re-radiograph if in any doubt.
  • If barium administered while food still present in stomach this may mimic pathological filling defects.

Step 2 - Additional radiographic projections

  • Follow-up film at 24 hours may be useful for demonstrating retention of barium in stomach, eg foreign body or ulceration.
  • If trying to identify position of stomach take lateral and VD views at 30-40 min when barium is in stomach and small intestine.
  • Double-contrast views give superior mucosal detail, this is the best procedure to identify a gastric ulcer but views are often difficult to interpret.

Aftercare

Immediate

Potential complications

  • Aspiration of barium either during administration or after procedure if patient vomits.

Outcomes

Reasons for Treatment Failure

  • Inadequate patient preparation, ie stomach not empty.
  • May not identify mucosal lesions or motility disorders.
  • Poor gastric distension.
  • Failure to obtain sufficient radiographs - lesion must be consistent on several films for diagnosis to be made.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Evans S M & Biery D N (1983) Double contrast gastrography in the cat; technique and normal radiographic appearance. Vet Radiol 24 (1), 3-5 VetMedResource.
  • Evans S M (1983) Double versus single contrast gastrography in the dog and cat. Vet Radiol 24 (1), 6-10 VetMedResource.

Other sources of information

  • Brawner R W & Bartels J E (1983) Contrast radiography of the digestive tract. Vet Clin North Am 13, 599-626.
  • Hall J A & Watrous B J (2000) The effect of pharmaceuticals on radiographic appearance of selected examinations of the abdomen and thorax. Vet Clin North Am Small Anim Pract 30 (2), 1-29.