Update on gastrointestinal imaging.

The current status of three gastrointestinal imaging techniques-positron emission tomography (PET) with 18 F-fluorodeoxyglucose (FDG), computed tomographic (CT) colonography, and magnetic resonance cholangiography (MRC)--are reviewed here. FDG-PET should not be used as an initial means to identify patients with primary colorectal malignancy; for the detection of colorectal carcinoma metastases and recurrence, contrast-enhanced CT should be used to monitor patients, with the use of PET reserved for equivocal cases. CT colonography is comparable to colonoscopy for the detection of patients with colorectal polyps > or = 1 cm, and its advantages include its capability of detecting extracolonic abnormalities. MRC is a relatively new application of MR imaging, with utility in multiple clinical settings, including patients with suspected obstructive disease, choledochal cysts, primary sclerosing cholangitis or AIDS cholangiopathy, biliary-enteric anastomoses, and patients with failed or inadequate endoscopic retrograde cholangiograms.