retrograde pyelography, a radiological technique for examining the structures of the collecting system of the kidneys that is especially useful in locating a urinary tract obstruction. A radiopaque contrast medium is injected through a urinary catheter into the ureters and the calyces of the pelves of the kidneys. Rarely, severe anaphylactoid reaction to the medium may occur because of a patient’s hypersensitivity to the iodine in the medium, and infection or trauma may result from the catheterization.
