Uniformity of Oral Contrast Material in the Bowel

Although positive oral contrast agents are used for the majority of abdominopelvic CT scans
in the United States, the quality of bowel opacification has not been compared between the
three major classes of positive oral contrast material (barium sulfate, ionic iodinated
contrast material, and non-ionic iodinate contrast material). The investigators will
retrospectively identify 250 patients each who received oral barium sulfate, diatrizoate,
and iohexol for CT scanning of the abdomen and pelvis (total 750 patients) and assess the
quality of bowel lumen opacification by the positive oral contrast agents.

Primary objective:

- To show the uniformity of bowel opacification is different between the three main types
of CT oral contrast material used in the United States (Barium sulfate, Diatrizoate,
and Iohexol).

Secondary objectives:

- To show whether or not one of the oral contrast agents provides more uniform
opacification than the others in the proximal or distal bowel

- To assess the relative opacification of the distal small bowel (ileum) by the three
contrast agents.

Inclusion Criteria:

- CT scans in which oral contrast material was given

Exclusion Criteria:

- CT scans in which an obvious paucity of oral contrast material is seen,

- CT scans of patients who had studies within 1 week prior where enteric contrast may
have been given, including fluoroscopic, endoscopic, or interventional studies