Each kidney Kidneys The kidneys are bean-shaped organs that figure prominently in the urinary tract. Each is about 4 to 5 inches (12 centimeters) long and weighs about one third of a pound (150 grams). One lies... read more continuously filters waste from the blood to produce urine. The urine then drains through the 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 into the bladder Bladder The bladder is an expandable, muscular sac. Urine accumulates in the bladder as it arrives from the ureters. The bladder gradually increases in size to accommodate an increasing volume of urine... read more at a low pressure. From the bladder, urine drains through the urethra Urethra The urethra is a tube that drains urine from the bladder out of the body. In men, the urethra is about 8 inches (20 centimeters) long, ending at the tip of the penis. In women, the urethra is... read more 
to exit the body. In males, the urethra is located in the penis. In females, the urethra ends in the vulvar area (the area of the external female genital organs).
A Look Inside the Urinary Tract
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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
Urinary reflux can cause frequent urinary tract infections Urinary Tract Infection (UTI) in Children A urinary tract infection is a bacterial infection of the urinary bladder ( cystitis), the kidneys ( pyelonephritis), or both. Urinary tract infections are caused by bacteria. Infants and younger... read more (UTIs). Severe reflux and frequent infections can damage the kidneys and ureters over time. Kidney damage can cause high blood pressure High Blood Pressure High blood pressure (hypertension) is persistently high pressure in the arteries. Often no cause for high blood pressure can be identified, but sometimes it occurs as a result of an underlying... read more 
and rarely kidney failure Overview of Kidney Failure Kidney failure is the inability of the kidneys to adequately filter metabolic waste products from the blood. Kidney failure has many possible causes. Some lead to a rapid decline in kidney function... read more .
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 uses high-frequency sound (ultrasound) waves to produce images of internal organs and other tissues. A device called a transducer converts electrical current into sound waves... read more 
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 During imaging tests, contrast agents may be used to distinguish one tissue or structure from its surroundings or to provide greater detail. Contrast agents include Radiopaque contrast agents... 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.
