Final answer:
Retrograde urography is the procedure involving the injection of contrast medium into the renal pelvis via a urethral catheter for urinary tract visualization.
Step-by-step explanation:
The radiologic procedure that requires a contrast medium to be injected into the renal pelvis via a catheter placed within the urethra is Retrograde urography. This procedure is used to visualize the structures of the urinary tract, including the kidneys, ureters, and bladder. During retrograde urography, a catheter is inserted into the urethra and guided up the urinary tract to the level of the renal pelvis, where the dye is then introduced to outline these structures on X-ray images.