What are the indications for a small bowel follow through?
A small bowel follow-through may be performed whenever small bowel disease is suspected. The patient drinks a large volume (750 to 1000 mL) of thin barium, and a single-contrast examination of the esophagus, stomach, and small bowel is performed. Barium filling of the small bowel is limited by gastric emptying at the pylorus. The radiologist is unable to distend all the loops of small bowel either quickly or at the same time. A small bowel follow-through is also limited by the normal 30- to 120-minute transit time from the pylorus to the ileocecal valve. The radiologist cannot stand in the fluoroscopic suite for 1 to 2 hours and watch the barium flow down the small bowel. The radiologist examines the patient at 15- to 30-minute intervals, palpating loops of small bowel when they are optimally distended with barium. A small bowel follow-through relies on fluoroscopically obtained spot radiographs, not overhead images.
A water-soluble contrast agent is used if bowel perforation is strongly suspected. A water-soluble contrast study of the small bowel is often suboptimal, however, because the hyperosmolar water-soluble contrast agent draws fluid into the lumen and prevents fluid resorption. The water-soluble contrast agent is diluted, and the images are very difficult to interpret. If a gastric or proximal small bowel leak is suspected, a water-soluble contrast upper GI study and proximal small bowel follow-through usually suffice. If a mid- to distal small bowel leak is suspected, a computed tomography (CT) scan may be the better initial test. If a very distal small bowel leak or anastomotic leak is suspected in a patient with an ileocolic anastomosis, a water-soluble contrast enema is probably the best examination.