Single-contrast (SC) and double-contrast (DC) colon examinations were compared in 425 consecutive patients for detection of polyps and stricturing carcinomas. Each patient was examined with both SC and DC during the same session. In patients with carcinoma, there was no significant difference between the two modalities. DC was far superior to SC for detection of rectal or colonic polyps (p less than 0.05); however, the techniques appeared to be complementary in the sigmoid and cecum. The authors conclude that DC is superior to SC as a means of screening for polyps of the rectum and colon, with SC being useful as an adjunct in problem areas such as the sigmoid and cecum.

The diagnostic value of biphasic radiographic examination of the stomach and duodenum was compared with that of fiberoptic endoscopy in a prospective, blinded study of 385 patients with dyspepsia. This investigation was directed at gastric malignancies and peptic ulcers. Methodologically there is no absolute standard for a study of this kind because histologic examination is useful for detection of cancer but inadequate for ulcers. As an alternative, kappa indexes and the sensitivity and specificity, as derived by Hui and Walter, were calculated and compared. For the detection of gastric carcinoma, radiographic and endoscopic findings had almost perfect agreement beyond chance. For gastric ulcers, radiography and endoscopy had substantial agreement, which became perfect if small ulcers (less than 5 mm) were excluded. For duodenal ulcers, radiography had a lower sensitivity than endoscopy; this disagreement disappeared if small ulcers were excluded. Both methods have equal merit; choice of the initial diagnostic procedure will therefore depend on cost, discomfort to the patient, and risk of complications.

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