During a cystoscopy, a narrow catheter (diameter of 1.3 mm) is inserted through the bladder into both ureters. It can be pushed up into the renal pelvis. Iodinated X-ray contrast agent is then injected so that the renal pelvis, ureter, and chalices are displayed under an image intensifier (fluoroscopy/X-ray machine). Differences in the contrast agents can then be recognised as stones or tumours. Using the same thin ureteral catheter, urine can be obtained for further testing.