Composition of iodobenzoic acid derivatives for visualization of the gastrointestinal tract

Disclosed are contrast agents of the formula or a pharmaceutically acceptable salt thereof, contained in aqueous compositions and methods for their use in diagnostic radiology of the gastrointestinal tract wherein Z = H, halo, C1-C20 alkyl, cycloalkyl, lower alkoxy, cyano, where the alkyl and cycloalkyl groups can be substituted with halogen or halo-lower-alkyl groups; R = C1-C25 alkyl, cycloalkyl, or halo-lower-alkyl, optionally substituted with halo, fluoro-lower-alkyl, aryl, lower-alkoxy, hydroxy, carboxy, lower-alkoxy carbonyl or lower-alkoxy-carbonyloxy, (CR1R2)p - (CR3 = CR4)mQ, or (CR1R2)p - C IDENTICAL C - Q; R1, R2, R3 and R4 are independently lower-alkyl, optionally substituted with halo; x is 1-3 y is 1-4; n is 1-5; m is 1-15; p is 1-10; and Q is H, lower-alkyl, lower-alkenyl, lower-alkynyl, lower-alkylene, aryl, or aryl-lower alkyl in an aqueous, pharmaceutically acceptable carrier.