Can anyone explain the term "Retrograde Pyelogram" to me? Is it a Medical procedure, or an Affliction?

It is a procedure wherein a dye is injected from the outside (urethra) to the inside (kidney) - thus being retrograde. The more comon procedure/test is an IVP (intravenous pyelogram) wherein a dye in injected into a vein and the dye is excreted through the kidneys to the bladder and then out the urethra. X-rays are taken along the way - these tests are usually done to determine a structural or functional abnormality of the urinary tract.