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Overview of Kidney and Urinary Tract Birth Defects

By Ronald Rabinowitz, MD, Professor of Urology and Pediatrics, University of Rochester Medical Center ; Jimena Cubillos, MD, Associate Professor of Clinical Urology and Pediatrics, University of Rochester School of Medicine and Dentistry

Birth defects are more common in the kidney and urinary system (urinary tract) than in any other system of the body. Defects can develop in the

  • Kidneys (the two organs that filter waste from the blood to make urine)

  • Ureters (the tubes that transport urine from the kidneys to the bladder)

  • Bladder (the expandable, muscular sac that holds urine)

  • Urethra (the tube that drains urine from the bladder out of the body)

A Look Inside the Urinary Tract

Did You Know...

  • Birth defects are more common in the kidneys and urinary system than in any other systems of the body.

Complications of urinary tract defects

Urinary tract defects may

  • Block or slow the flow of urine

  • Allow urine to flow backwards from the bladder to the kidneys (urinary reflux)

Any birth defect that blocks or slows the flow of urine can cause urine to become stagnant, which can result in urinary tract infections (UTIs) or formation of kidney stones.

Urinary reflux usually happens when defects involve the junction where the two ureters connect to the bladder. Normally these junctions (one for each ureter) allow urine to flow only one way, from the kidneys to the bladder. Defects of the junction can allow urine to flow backward from the bladder into the kidneys (urinary reflux). In addition, other defects that block the flow of urine can increase the pressure in the bladder and cause urinary reflux.

Urinary reflux and/or frequent infections can damage the kidneys and ureters over time. Kidney damage can cause high blood pressure and rarely kidney failure.

Severe urinary tract defects in a fetus can cause little or no urine to be produced. The fetus's urine becomes part of the fluid that surrounds the fetus in the uterus (called amniotic fluid). If the fetus does not release enough urine, the amount of amniotic fluid is reduced. If there is too little amniotic fluid, the fetus's lungs, heart, face, and limbs may develop abnormally. Severe defects can cause death while the fetus is in the womb or shortly after birth.


Many urinary tract defects cause no symptoms and are often discovered only when imaging studies are done for other reasons, or during the well-child examination. Some kidney defects do not cause problems or become known until adulthood.

When urinary tract defects do cause symptoms, children may have

Children who have urinary obstruction are also at increased risk of significant urinary bleeding after a minor injury because the kidney is under pressure.


  • Before birth, prenatal ultrasonography and blood tests

  • After birth, imaging tests and sometimes cystoscopy

  • Sometimes voiding cystourethrography

Before birth, urinary tract defects are often discovered by doctors during routine prenatal ultrasonography or other routine screening tests for hereditary disorders.

After birth, if doctors suspect a child has a urinary defect, they typically do imaging tests such as ultrasonography, computed tomography (CT), nuclear scans, and magnetic resonance imaging (MRI). Rarely, doctors do intravenous urography or cystoscopy. In cystoscopy, doctors look inside the bladder and urethra through a flexible viewing tube called a cystoscope (a type of endoscope).

To diagnose certain defects of the urinary tract, doctors sometimes do a test called voiding cystourethrography (VCUG). For voiding cystourethrography, a catheter is passed through the urethra into the bladder, a liquid dye that shows up on x-rays (contrast agent) is put through the catheter, and x-rays are taken before and after the child urinates.


  • Sometimes surgery

Defects that cause symptoms or those that lead to increased pressure in the kidneys or bladder usually need to be surgically corrected.

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