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Background After patients have undergone colonoscopic polypectomy, it is uncertain whether colonoscopic examination or a barium enema is the better method of surveillance. Methods As part of the National Polyp Study, we offered colonoscopic examination and double-contrast barium enema for surveillance to patients with newly diagnosed adenomatous polyps. Although barium enema was performed first, the endoscopist did not know the results. Results A total of 973 patients underwent one or more colonoscopic examinations for surveillance. In the case of 580 of these patients, we performed 862 paired colonoscopic examinations and barium-enema examinations that met the requirements of the protocol. The findings on barium enema were positive in 222 (26 percent) of the paired examinations, including 94 of the 242 colonoscopic examinations in which one or more adenomas were detected (rate of detection of adenomas, 39 percent; 95 percent confidence interval, 33 to 45 percent). The proportion of examinations in which ...

Numerous studies of vertebral arteriography have established the normal positions of the individual arteries in the posterior fossa.1-3The precise localization of expanding mass lesions by displacement and distortion of these arteries has been more difficult, however, than with displacement and distortion of the supratentorial arteries.4Only rarely are vascular displacements in the posterior fossa of definite localizing value. One example would be the posterior displacement of the basilar artery by a mass in the region of the clivus. Many other displacements which can be noted in the vertebral arteriograms of patients with posterior fossa mass lesions are of less localizing significance. Examples of these would be the anteroposterior or midline displacement of the cranial loop of the posterior inferior cerebellar artery,5and displacements and distortions of the posterior cerebral arteries,6especially when due to tentorial herniation. Downward displacement of the caudal loop of the