CausesBy Mayo Clinic staff
Your urinary system includes your kidneys, ureters, bladder and urethra. All play a role in removing waste products from your body.
The kidneys, a pair of bean-shaped organs at the back of your upper abdomen, filter waste, water and electrolytes — minerals, such as sodium, calcium and potassium, that help maintain the balance of fluids in your body — from your blood. Tubes called ureters carry urine from your kidneys down to your bladder, where it is stored until it exits the body through another tube (the urethra) during urination.
Vesicoureteral reflux can develop in two forms, primary and secondary:
- Primary vesicoureteral reflux. The cause of this more common form is a defect that's present before birth (congenital). The defect is in the functional valve between the bladder and a ureter that normally closes to prevent urine from flowing backward. As the child grows, the ureters lengthen and straighten, which may improve valve function and eventually resolve the reflux. This type of vesicoureteral reflux tends to run in families, which indicates that it may be genetic, but the exact cause of the defect is unknown.
- Secondary vesicoureteral reflux. The cause of this form is a blockage or malfunction in the urinary system. The blockage most commonly results from recurrent UTIs, which may cause swelling of a ureter.
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