Dilute contrast media in diagnosis of lesions of the colon.

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The roentgenologist bears the responsibility for diagnosis of lesions of the colon above the level of direct visualization by the sigmoidoscope. With improved x-ray technic and dissemination of knowledge of methods of examination, there has been steady progress in diagnostic accuracy. There still remains, however, a reducible error, particularly in relation to small lesions of the colon. As has been repeatedly emphasized, early and accurate diagnosis of small lesions, particularly those of a polypoid type, offers the best hope for successful treatment of cancer of the colon. The relationship of the two conditions has been well established. However, the probable multiplicity of polyps of the colon or rectum de serves re-emphasis. Statistical observations indicate that lesions of the colon or rectum will be multiple in 30 to 40 per cent of all cases (1, 4). We, as roentgenologists, should not be content, therefore, to think that our job is done when the presence of a single polyp has been established by x-ray examination. Such a finding, either by sigmoidoscopy or x-ray study, should be the signal for a careful search, which can be considered complete only when every portion of the bowel above the range of direct vision has been critically demonstrated on films with whatever contrast method is used. Repeated examination may be necessary for reasonable assurance that all portions have been covered, particularly in the presence of long redundant sigmoid colon loops which may be fixed in the pelvis. Close co-operation with the examining sigmoidoscopist is required, to make sure that no part of the bowel has escaped observation either by direct vision or x-ray examination. Faced daily with these problems, we naturally seek methods which will permit easier and more accurate diagnosis. Because of the limitations of present-day fluoroscopic methods, most small lesions will be discovered on film studies, with one or another contrast technic. Gross lesions may be detected by any or all of the usual methods. For the past five years we have used in special studies of the colon, and for a shorter time in routine studies, a contrast medium of lesser density (3) than that which is usually employed. Barium suspensions with approximately 4.5 ounces of barium sulfate to a quart of water, with suitable suspending agents,2 have been found to be sufficiently dense to show a good outline of the filled colon, both fluoroscopically and on the roentgenogram. At the same time displacement of the medium by small intraluminal masses can be appreciated on critical films made with high-kilovoltage technic. The aim has been to fill the bowel with a medium of sufficiently low density so that the density variation resulting from displacement of the medium by small intraluminal masses is not obliterated. We wish to achieve contrast within the bowel. Contrast between the contour of the filled colon and the surrounding tissue is easy to obtain.