Contributors: Barbara J Watrous

 Species: Feline   |   Classification: Techniques

Introduction Requirements Preparation Procedure Aftercare Outcomes Further Reading

Introduction

  • Administration of positive contrast agent to provide information about the lumen of the gastrointestinal tract and to give crude assessment of gastrointestinal transit time.
  • Visualization of mucosal surfaces of gastrointestinal tract.
  • Allows assessment of gastrointestinal wall thickness.

Uses

  • Identification of position of gastrointestinal tract if not visible on plain radiographs, eg in suspect diaphragmatic hernia Diaphragm: hernia , ascites.
  • Allows some assessment of gastrointestinal transit time.
  • Identification of radiolucent gastrointestinal foreign bodies Intestine: foreign body - linear .
  • Investigation of vomiting Vomiting .
  • Investigation of abdominal mass Abdominal organomegaly .
  • Investigation of abdominal pain.
  • Investigation of melena.
  • Investigation of weight loss.

Advantages

  • Simple.
  • Relatively non-invasive.

Disadvantages

  • Time-consuming and moderately expensive (cost may be comparable to exploratory laparotomy).
  • May give minimal information if total gastrointestinal obstruction as barium may not reach the site of obstruction.
  • Often normal in cases of chronic diarrhea.
  • Does not provide information about large intestine (a barium enema Radiography: large intestine contrast or pneumocolon is required).

Technical Problems

  • Requires considerable experience and knowledge of normal appearance of study to interpret films.

Alternative Techniques

  • Fluoroscopy (provides more information about motility).
  • Ultrasonography (may give more accurate assessment of intestinal wall).
  • Endoscopy .
  • Radiopaque markers (BIPs) - require fewer radiographs to provide information on gastric emptying and GI motility but does not give anatomic or morphologic information.
  • Scintigraphy (Provides more information on gastrointestinal function and can assess solid and liquid phase gastric emptying. May also be useful in identifying site of GI bleeding).

Time Required

Preparation

  • 20 min.

Procedure

  • Up to 24 hours depending on results.

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

  • Is animal sufficiently stable to tolerate prolonged procedure before diagnosis?
    If laparotomy is anticipated may be prudent to perform endoscopy/laparotomy instead.
  • Assess hydration of animal prior to study.
  • If suspect gastrointestinal tract rupture it is theoretically safer to use a water-soluble contrast agent.
  • However gastrointestinal tract rupture will require surgery and abdominal lavage so leakage of barium is of minor importance.
    Iodine-based contrast agents may exacerbate hypovolemia and tend to get diluted as they pass through gastrointestinal tract, producing increasingly poor contrast. They may readily pass through partial obstruction and therefore hide diagnosis.

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.
  • Stomach tube.
  • Means of keeping mouth open for stomach tubing, eg inner part of bandage roll.
  • Large syringe.

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.
  • Positive contrast agent.
  • Lubricant (for stomach tubing).

Preparation

Dietary Preparation

  • Food should be withheld for 12-24 hours.
  • May need to withhold food for 24 hours if suspect delayed gastric emptying.

Restraint

  • Sedation/anesthesia should be avoided if possible as this often affects GI transit time.
  • Low dose acepromazine Acepromazine maleate 0.05-0.1 mg/kg has minimal effect on GI motility. A combination of acepromazine Acepromazine maleate (0.1 mg/kg) and butorphanol Butorphanol tartrate (0.05 mg/kg) slows GI movement, but may be acceptable.
  • Diazepam Diazepam delays gastric emptying.

Other Preparation

  • Warm water enema   Enema  the night before and not within 2-3 hours of study if feces present in colon.

Choice of contrast

  • Micronized barium sulfate as suspension is preferred (usually 15% w/v):Commercially prepared suspension less likely to clump.
    • May be bought as a suspension or powder to mix with water.

Procedure

Approach

Step 1 - Control films

  • Lateral and ventrodorsal abdominal radiographs Radiography: abdomen:
    • Check exposure settings (requires low kV and high mAs) and processing.
      Increase exposure by 5 kV from control film.
    • Confirm positioning adequate.
    • Confirm diagnosis not apparent without contrast study.

Step 2 - Pass stomach tube

  • Measure length of stomach tube needed from mouth to cranial abdomen of animal and mark tube.
  • Stomach tube patient Stomach tubing.
  • Inject small amount of sterile water/saline to ensure tube correctly placed in gastrointestinal tract and not respiratory tract.

Core Procedure

Step 1 - Administer contrast

  • Administer micronized barium sulfate suspension 5-10 ml/kg.
  • Remove stomach tube.

Step 2 - Obtain radiographic views

  • See abdominal radiography for positioning technique Radiography: abdomen.
  • Immediately take left and right lateral, VD and DV radiographs.
  • Repeat all four views after 10 min.
  • Take lateral and VD radiographs at regular intervals (typically every 10-30 min) depending on rate of passage of barium.

Exit

Step 1 - Assess radiographs

  • Ensure apparent lesions are consistent over time and on multiple views.
  • Continue radiography until a diagnosis has been made or barium has reached the large intestine, and stomach is empty.
  • A 24 hour radiograph may be useful to identify barium retained in stomach or small intestine (all barium should be in large intestine after 24 hours).

Step 2 - Additional radiographic procedures

  • Number of radiographs taken will vary according to purpose of investigation.
  • If wanting to assess position of stomach and small intestine a lateral and ventrodorsal radiograph after 30-40 min may be sufficient.
  • If investigating suspected small intestinal lesions radiographs may need to be taken every 15-30 min.

Aftercare

Immediate

Potential complications

  • Administration of iodine-based contrast agents may exacerbate hypovolemia as these draw fluid into intestinal lumen and may cause vomiting

Outcomes

Complications

  • Bowel perforation with barium leakage can result in granuloma formation.
  • Aspiration of barium - most likely if syringing barium into buccal pouch.

Reasons for Treatment Failure

  • Mucosal lesions may be missed.
  • Barium may fail to reach site of obstruction in total intestinal obstruction.
  • Inadequate volume of barium administered can produce incomplete filling of small intestine.
  • Dilution of iodine-based contrast agents on passage through gastrointestinal tract may make identification of distal small intestinal lesions difficult.
  • Poor knowledge of normal variations, eg Peyers patches, peristalsis may result in erroneous diagnosis.
  • Excessive barium may make interpretation of mucosal detail difficult.
  • Inadequate number of films taken (must be able to see abnormalities consistently on several films).

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Herrtage M E & Dennis R (1987) Contrast media and their use in small animal radiology. JSAP 28 (12), 1105-1114 VetMedResource.

Other sources of information

  • Gomez J A (1974) The gastrointestinal contrast study - methods and interpretation. Vet Clin North Am 4, 805-842.