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What Are the Causes of OAB?

Overactive Bladder

How the Urinary Tract Works Normally, and What Causes OAB

The urinary tract   is the important system in our bodies that removes liquid waste (urine). It includes the organs that produce, store and pass urine. These are:

  • Kidneys: two bean-shaped organs that clean waste from the blood and make urine.

  • Ureters: two thin tubes that take urine from the kidney to the bladder.

  • Bladder: a balloon-like muscular sac that holds urine until it’s time to go to the bathroom.

  • Urethra: the tube that carries urine from the bladder out of the body. The urethra has a muscle called a sphincter that locks in urine.

  • The sphincter muscle opens to release urine when the bladder contracts.

Overactive Bladder
Overactive Bladder

Normally, when your bladder is full of urine waste, your brain signals the bladder. The bladder muscles then squeeze. This forces the urine out through the urethra. The sphincter in the urethra opens and urine flows out. When your bladder is not full, the bladder is relaxed.

With a healthy bladder, signals in your brain let you know that your bladder is getting full or is full, but you can wait to go to the bathroom. With OAB, you can’t wait. You feel a sudden, urgent need to go. This can happen even if your bladder isn’t full.

If the nerve signals between your bladder and brain don’t work properly, OAB can result. The signals might tell your bladder to empty, even when it isn't full. OAB can also be caused when muscles in your bladder are too active. This means that the bladder muscles contract to pass urine before your bladder is full. In turn, this causes a sudden, strong need to urinate. We call this "urgency."

Risk Factors for OAB

  • Neurologic disorders or damage to the signals between your brain and bladder
  • Hormone changes
  • Pelvic muscle weakness or spasms
  • A urinary tract infection
  • Side effects from a medication
  • Diseases that affect the brain or spinal cord, like stroke and multiple sclerosis

If you think you have OAB, talk with your health care provider. It’s important to learn why it’s happening so you can manage your symptoms.