RGP stands for retrograde pyelography. It is the radiographic examination of the renal pelvis and ureter by means of contrast medium injection via a retrogradely introduced ureteric catheter. The catheter is pushed into the ureter or renal pelvis via a cystoscopic approach through the urinary bladder. The procedure is done to delineate the site of ureteric or renal pelvis pathology (tumour, stones etc.) which cannot be demonstrated otherwise.