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

It is a procedure so the doctor can see the kidney and ureter (tube that takes urine from the kidney to the bladder). You are given an injection of a 'contrast agent' into the vein, usually the arm. This is removed from the bloodstream via the kidneys, and the doctor is able to see it on x-rays. X-rays are taken at intervals as it goes through the different parts of the urinary system.