Contributors: Barbara J Watrous
Species: Canine | Classification: Techniques
- Use of positive, negative or a combination of contrast agents to highlight the gastric lumen.
- Identification of the position of the stomach, eg in ascites or if suspect gastric displacement, eg diaphragmatic hernia Diaphragm: traumatic hernia.
- Assessment of lumen size and gastric axis if stomach not visible on plain films.
- Relatively simple procedure in most patients.
- Often difficult to assess subtle mucosal lesions.
- Not very accurate for assessment of motility disorders.
- Difficult to interpret if not familiar with normal appearance.
- 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).
- Barium impregnated polyurethane spheres (BIPs).
- 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.
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?
- 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.
- X-ray machine.
- Processing facilities.
- Protective clothing (lead apron) for radiographer.
- Positioning aids (sandbags, cradle and ties).
- Method of labelling film.
- Large syringe.
- Means of keeping mouth open for stomach tubing, eg inner part of bandage roll.
- Stomach tube.
- 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.
- Grid for examination of large dog.
- Mouth gag.
- Radiographic film.
- Contrast agent.
- Water-soluble lubricant for stomach tubing.
- Withhold food 12-24 hours prior to procedure.
- Low dose of acepromazine Acepromazine maleate (0.05-0.1 mg/kg) has minimal effect of 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.
- If performing negative or double contrast studies gastric motility can not be assessed so effect of sedation is unimportant.
- 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.
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
- 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.
- Air (4-8 ml/kg).
- Carbon dioxide/air.
- Suitable for assessing position of stomach and identifying foreign bodies and gross wall thickening.
- Double contrast: provides best information on mucosal detail.
Step 3 - Insert stomach tube
- Insert premeasured length of stomach tube to level of stomach.
- Inject small amount of water/saline to ensure tube correctly placed in stomach and not respiratory tract.
Step 1 - Instil contrast agent
- Inject (negative or positive) contrast in sufficient quantity to distend stomach.
Tendency to underfill stomach in most cases.
- Dose 5-12 ml/kg (with reduced dose rate for larger dogs).
- Administer 1-3 ml/kg of barium - lower doses for larger dogs.
- Roll animal through 360° then restomach 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.
Step 1 - Assess radiographs
- Ensure stomach adequately distended for interpretation.
- Stomach contractions may mimic pathology, including mural thickening and stenosis - if in doubt repeat radiograph.
- If barium is administered when food is 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.
- Aspiration of barium either during administration or after procedure if patient vomits.
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.
- Recent references from PubMed and VetMedResource.
- Miyabayashi T & Morgan J P (1991) Upper gastrointestinal examinations - a radiographic study of clinically normal beagle puppies. JSAP 32 (2), 83-88 VetMedResource.
- Evans S M (1983) Double versus single contrast gastrography in the dog and cat. Vet Radiol 24 (1), 6-10 VetMedResource.
- Evans S M & Laufer I (1981) Double contrast gastrography in the normal dog. Vet Radiol 22 (1), 2-9 Wiley Online Library.
Other sources of information
- 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 S A Pract 30 (2), 349-377, vii PubMed.
- Brawner W R Jr. & Bartels J E (1983) Contrast radiography of the digestive tract. Indications, techniques, and complications. Vet Clin North Am S A Pract 13 (3), 599-626 PubMed.
- American College of Veterinary Radiology, Executive Director: Dr M Bernstein, PO Box 87, Glencoe, IL 60022, USA. www.acur.ucdavis.edu.