Merck Manual

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Urinary Reflux

(Vesicoureteral Reflux)


Ronald Rabinowitz

, MD, University of Rochester Medical Center;

Jimena Cubillos

, MD, University of Rochester School of Medicine and Dentistry

Reviewed/Revised Aug 2022 | Modified Sep 2022
Topic Resources

Urinary reflux is when urine flows backward from the bladder into the ureter and sometimes the kidney, usually because of a birth defect of the urinary tract.

The Kidneys
The Ureters, Bladder, and Urethra

A Look Inside the Urinary Tract

A Look Inside the Urinary Tract

Causes of Urinary Reflux

People normally have two ureters Ureters The ureters are muscular tubes—about 16 inches (40 centimeters) long—that attach at their upper end to the kidneys and at their lower end to the bladder. (See also Overview of the Urinary Tract... read more . One ureter connects the left kidney to the bladder, and the other ureter connects the right kidney to the bladder. Many birth defects of the bladder Bladder Defects There are several different birth defects that affect the bladder (the expandable, muscular sac that holds urine). Some are apparent at the doctor's examination. Others require tests to evaluate... read more or birth defects of the ureters Ureter Defects Ureters are the tubes that transport urine from the kidneys (the two organs that filter waste from the blood to make urine) to the bladder (the expandable, muscular sac that holds urine). People... read more involve the junction where a ureter connects to the bladder. Normally the junction allows urine to flow only one way, from the kidneys to the bladder. Defects of the junction can allow urine to flow back up the ureter and sometimes into the kidneys. In addition, other defects that block the flow of urine can increase the pressure in the bladder and cause urinary reflux. Reflux can affect one side or both sides.

Complications of urinary reflux

Symptoms of Urinary Reflux

Urinary reflux itself does not cause symptoms. But children may have symptoms if a urinary tract infection develops. Then children may have fever, may have pain in their abdomen or back, and may urinate more than normal or have burning when they urinate.

Diagnosis of Urinary Reflux

  • Voiding cystourethrography or radionuclide cystography

Doctors suspect urinary reflux if babies or young children have a urinary tract infection that is severe enough to cause fever. Some children are brought to a doctor because they have a sibling who was diagnosed with urinary reflux, and siblings of children with urinary reflux are at increased risk of developing the disorder. In both cases, doctors usually do ultrasonography Ultrasonography Ultrasonography is a type of medical imaging that uses high-frequency sound (ultrasound) waves to produce images of internal organs and other tissues. During an ultrasound, a device called a... read more Ultrasonography of the urinary tract to look for abnormalities.

If the ultrasonography results are abnormal or if the child keeps having urinary tract infections, doctors may do a more complicated test called voiding cystourethrography Cystography and cystourethrography There are a variety of tests that can be used in the evaluation of a suspected kidney or urinary tract disorder. (See also Overview of the Urinary Tract.) X-rays are usually not helpful in evaluating... read more . For voiding cystourethrography, a catheter is passed through the urethra into the bladder, a liquid that shows up on x-rays (contrast agent Radiopaque Contrast Agents Radiographic contrast agents are substances used to distinguish between internal structures in medical imaging, such as various types of x-rays and magnetic resonance imaging (MRI). During imaging... read more ) is put through the catheter, and x-rays are taken before and after the child urinates.

Radionuclide cystography is similar to voiding cystourethrography except that a radioactive agent is placed in the bladder and images are taken using a nuclear scanner. This test exposes the child's ovaries or testes to less radiation than voiding cystourethrography. Urinary reflux can be diagnosed only with radionuclide cystography or voiding cystourethrography.

Treatment of Urinary Reflux

  • Sometimes preventive (prophylactic) antibiotics

  • Sometimes surgery

Treatment of urinary reflux depends on the specific birth defect and also on the severity of the complications.

Children who have few symptoms and no complications usually do not require treatment, as many will outgrow the reflux.

Daily antibiotics to prevent infection are sometimes given to children who have severe reflux, frequent UTIs with fever, or both. Children with severe reflux also may need surgery to correct the problem and ensure urine drains properly.

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