What is RGP and why is it done?

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.