Colonoscopically detected colorectal cancer missed on barium enema

The radiographs and clinical records of 26 patients with colorectal cancer missed on barium enema, and subsequently detected at colonoscopy, were reviewed to determine the cause of radiological error. Twenty (77%) of the patients were female. In 24 of 26 patients, anemia and/or rectal bleeding was a presenting feature. Fourteen of the 26 (54%) missed cancers were in the sigmoid colon, 10 (38%) in the ascending colon or hepatic flexure, and two (8%) in the rectum. Tumor size ranged from 20-100 mm. Fifteen were polyps, and 11 annular cancers. Fourteen (54%) were Dukes C or D tumors. Twenty-eight barium enemas in 23 patients were available for review: 86% were double-contrast studies. In 18 (76%), the cancer could be seen in retrospect and, in over half, the tumor was obvious. The dominant perceptive error was due to missing the lesion in the barium pool. Other major errors were missing the lesion en face or in overlapping loops. As most cancers were missed because of observer perceptive error, by both experienced and inexperienced radiologists, the authors recommend double reporting of all barium enemas.