False-colour X-ray of the abdominal & pelvic areas of a healthy person, featuring the left & right kidneys & ureters (the vessels connecting the kidneys to the bladder), which have been enhanced using intravenous pyelography (IVP). The technique involves prior intravenous injection of an iodine- based, radio-opaque contrast medium, which is concentrated & excreted by the kidneys. The branches of the renal pelvis (the structures of the kidney into which urine is drained) & the ureters (25-30 cm long in adults) are clearly defined in red. IVP tests kidney function & reveals stones in kidneys or ureters & other malfunctions of the urinary tract.