The most commonly utilized contrast materials for GI examinations include barium sulfate and Gastrografin.
Barium represents the most widely used contrast agent.
Gastrograffin is the other alternative to Barium swallow and is used somewhat less commonly. This is a water-soluble contrast agent that can be diluted to varying strengths and ingested in a similar manner as barium sulfate.
Gastrograffin may be used both as a liquid drink, or as an enema.
Chemically it is Diatrizoate Meglumine .
Generally speaking, barium produces higher quality images than Gastrograffin.
It has the downside of having a chalky taste that is somewhat upsetting to some patient. It also has the disadvantage of producing a chemical peritonitis should a bowel perforation be present and the barium spills freely into the peritoneal cavity.
If GI transit is delayed, water will be progressively absorbed from the barium compound within the gastrointestinal tract, producing hard concretions which can form in the colon and cause constipation.
Gastrograffin, on the other hand, is water-soluble and well suited to performing GI examinations where suspicion for bowel perforation exists.
It has the main disadvantage of an extremely foul taste and is often poorly tolerated by patients when administered full strength. It also has been known to cause severe chemical pneumonitis if aspiration occurs.
For this reason, Gastrograffin should only be administered with extreme caution in patients known to aspirate or given through a conduit in patients presenting with a high risk for aspiration.
Gastrograffin is also hyperosmotic and tends to draw fluid into the bowel lumen as it passes through the GI tract. While this can be advantageous in helping eliminate stool in the constipated patient, this could be disaster in patients presenting with small bowel obstructions, as the osmotic pressure will produce a more progressive dilatation of the small bowel in the obstructed patient.