When are oral and iv contrast materials for CT and MRI administered to patients with an acute abdomen or pelvis?
Oral contrast material distends and opacifies the bowel, allowing for better characterization of bowel pathologic conditions and separation of bowel structures from nonbowel structures. Intravenous contrast material aids in the characterization of pathologic lesions and allows for opacification and evaluation of vascular and urothelial structures. Both types of contrast material are generally administered in patients with an acute abdomen or pelvis prior to CT scanning whenever possible. In patients with a history of intravenous contrast allergy or renal insufficiency, intravenous contrast material is generally not administered, unless the patient has received a corticosteroid preparation or is scheduled to undergo dialysis after the CT examination. In patients with suspected urolithiasis, unenhanced CT without oral or intravenous contrast material is generally performed because unenhanced images are often sufficient for making a diagnosis. In patients undergoing CT angiography evaluation of the arterial vasculature, oral contrast material is generally not administered because it can obscure normal vessels and vascular pathologic conditions during multiplanar image reconstruction.
Oral contrast material is not routinely administered to patients undergoing MRI examination in the acute setting because the improved soft tissue contrast resolution allows for good visualization of the bowel wall and lumen. Intravenous gadolinium-based contrast material is routinely administered to patients undergoing MRI examination of the abdomen or pelvis in the acute setting. However, if there is a history of intravenous contrast allergy, renal insufficiency, or pregnancy, it is not administered.
