The effect of osmotic diuresis on urinary iodine concentration using contrast media of differing osmolality.

The urinary iodine concentrations of a monomer (sodium iothalamate), a dimer (sodium iocarmate) and a non-ionic compound (metrizamide) have been compared in dogs with varying levels of solute excretion. All the animals were undergoing maximal antidiuresis. In dogs with normal solute excretion, metrizamide and iocarmate produced higher urinary iodine concentrations than iothalamate. There was no significant difference between metrizamide and iocarmate. With increasing levels of solute excretion, the differences between the compounds were reduced. These findings suggest that contrast media of reduced osmolality are unlikely to have a special place in advanced renal failure.