[The "false-positive polyp" during contrast examination of the colon (author's transl)]

44 cases of false-positive radiological diagnosis of colonic polyps are reviewed with regard to cause, frequency, distribution and radiological criteria. Most common causes are scybala and air bubbles (77%) and effects of overlapping and projection (19%). Due to extensive folding of the colon misinterpretations are frequently seen in the sigmoid and in the area of both flexures; the folding allows overlapping of mucosal structures and trapping of bowel contents. The validity of roentgen signs in polyp diagnosis and the limits of colonoscopy are discussed. Diagnostic reliability may be improved by optimal technique of examination and standardized proceeding.