Use of low-osmolality contrast medium does not increase prevalence of medullary sponge kidney.

To assess the prevalence of intrapapillary linear collections of contrast medium as well as of homogeneous papillary blush on excretory urograms obtained with a low-osmolality contrast medium, iohexol was used in 300 patients. Intrapapillary linear collections of contrast medium (ie, three or more linear collections of contrast material within a papilla) were found in 10 (9.5%) of the 105 patients with renal stone disease and two (1.0%) of the 195 patients without nephrolithiasis (P less than .001). These prevalences are similar to those found in a previous study with use of a high-osmolality contrast medium (sodium amidotrizoate). The difference in the prevalence of homogeneous papillary blush between stone formers and non-stone formers was nonsignificant. The authors conclude that intrapapillary linear collections of contrast medium on excretory urograms obtained with use of a low-osmolality contrast medium should be considered to have the same clinical significance as those on excretory urograms obtained with use of a high-osmolality contrast medium, that is, as indicating the presence of medullary sponge kidney.