Your kidneys make urine by filtering wastes and extra water from your blood. The waste is called urea. Your blood carries it to the kidneys. From the kidneys, urine travels down two thin tubes called ureters to the bladder. The bladder stores urine until you are ready to urinate. It swells into a round shape when it is full and gets smaller when empty. If your urinary system is healthy, your bladder can hold up to 16 ounces (2 cups) of urine comfortably for 2 to 5 hours.
You may have problems with urination if you have
Some conditions may also cause you to have blood or protein in your urine. If you have a urinary problem, see your health care provider. Urinalysis and other urine tests can help to diagnose the problem. Treatment depends on the cause.
NIH: National Institute of Diabetes and Digestive and Kidney Diseases