Coloured 3D computed tomography (CT) scan of the abdomen showing the urinary system. The kidneys (upper centre right and left) filter waste products from the blood and excrete them as urine. The urine is carried from the kidneys to the bladder (yellow, bottom centre) by the ureters (tubes). The kidney at left has a duplicated ureter. This is a congenital condition where two ureters are present, both draining a single kidney.