Disclosed are x-ray contrast compositions for oral or retrograde examination of the gastrointestinal tract comprising a polymeric material capable of forming a coating on the gastrointestinal tract, said polymeric material having atoms containing polarizable electrons thereon, in combination with a divalent cation; and an x-ray contrast producing agent of the formula

or a pharmaceutically accetable salt thereof,
wherein
X = or
Z = H, halo, C 1 -C 20 alkyl, cycloalkyl, lower alkoxy, cyano, where the alkyl and cycloalkyl groups can be substituted with halogen or halo-lower-alkyl groups; R = C 1 -C 25 alkyl, cycloalkyl, aryl or halo-lower-alkyl, optionally substituted with halo, fluoro-lower-alkyl, lower-alkoxy, hydroxy, carboxy or lower-alkoxy carbonyl, lower-alkenyl, lower-alkynyl, lower-alkylene or lower-alkoxy-carbonyloxy, n is 1-5; y is 0-4; and w is 1-4,
in a pharmaceutically acceptable carrier and a method of its use in diagnostic radiology of the GI tract.