Osmolality is the number of moles of osmotically active particles (molecules) present in solution per kilogram of water.
High osmolality of contrast agents is related to some of the adverse reactions.

Osmolality of iodinated contrast media:

Reno-30® is a radiopaque contrast agent indicated for retrograde or ascending pyelography. Retrograde pyelography does not include systemic administration of contrast media, so the risk of adverse reactions is extremely rare.