Gastric and duodenal ulcers and perforation
Their radiographic identification is not easy, and necessitates high-quality images. Ulcerations are seen as out-pouching
of contrast on positive-contrast studies, because the contrast accumulates in the crater of the ulcer, if the ulcer is tangential
to the X-ray beam. When the X-ray beam strikes the ulceration perpendicularly, the lesion is seen "en face" and appears as
a focal pool of contrast medium surrounded by a lucent line representing a rim of wall thickening. In this region, there is
effacement of the normal rugal folds and an overall thickening of the gastric or duodenal wall. If fluoroscopy is used, decreased
motility of the affected wall segment may be observed.
If GI perforation is suspected, typical ultrasonographic signs of perforation, such as free fluid, hyperechoic mesentery and
free gas are relatively easily detected. It becomes more difficult in postoperative patients, where a certain degree of mesenteric
inflammation, fluid and gas in the abdomen are already present.
Patients with gastric peg-tubes and patients who are more painful, vomiting or generally not recovering as expected after
peg-tube placement or enterotomies often are evaluated with contrast radiography for GI tract leakage.
Traditionally, barium is not recommended for investigation of GI perforations because it has been shown to irritate the serosal
layers and peritoneum, causing chemical peritonitis. A water-soluble contrast agent should be administered initially to detect
a leak. However, small leaks can be difficult to detect because iodinated contrast is less opaque than barium.
If no leak is detected, barium should be added to rule out a small perforation, followed by laparotomy and peritoneal lavage
if leakage is present. Barium sulfate is a known safe method to diag-nose esophageal perforations.
Small intestinal obstructions
Interpretation of survey radiographs in patients with suspected mechanical obstruction can be difficult. Findings can be subtle,
and conditions such as enteritis can lead to a similar radiographic appearance. A simple contrast study to clearly localize
the colon and differentiate it from dilated small bowel loops is a pneumocolon.
The small intestines are more easily accessible with ultrasound than is the stomach, and upper GI studies are not routinely
performed anymore, but they are a good alternative to ultrasound to rule out foreign-body obstruction.
Surgeons often are concerned about complications after enterotomies in patients with intraluminal barium. However, barium's
effects on transmural wound healing of the GI tract appear minimal. Foreign bodies create a filling defect within the barium
column and, depending on the size of the foreign object (partial vs. complete obstruction), barium accumulation can be seen
oral to the obstruction.
Linear foreign bodies are visible only as filling defects if they have a certain thickness; nevertheless, the contrast agent
(barium or, in cats, also iodine) is helpful to better delineate the abnormal shape and contour of the bowel loops containing
the linear foreign body.
Infiltrative bowel disease
Contrast evaluation of patients with suspected infiltrative bowel disease are rarely performed anymore. Ultrasound provides
more information about extent of disease, integrity of wall layers and additional findings such as lymphadenopathy. In upper
GI series, neoplastic and non-neoplastic infiltrates result in a similar appearance. Main changes include irregular mucosal
surface, thickened wall, change of luminal diameter, corrugated appearance of the intestines and "thumbprinting" — irregularly
arranged indentations into the contrast column. These changes have to be differentiated from peristalsis, and have to be verified
on more than one radiographic view.
by Johnny D. Hoskins DVM, PhD, Dipl. ACVIM Dr. Hoskins is owner of Docu-Tech Services. He is a diplomate of the American College of Veterinary Internal Medicine with
specialities in small animal pediatrics. He can be reached at (225) 955-3252, fax: (214) 242-2200 or e-mail: email@example.com