Congenital Anomalies of the Kidneys and Urinary Tract

What are congenital anomalies of the kidneys and urinary tract?

Congenital anomalies of the kidneys and urinary tract are birth defects affecting the form and function of the kidneys and urinary tract.

Babies are usually born with two kidneys, which filter waste and excess liquid from the blood. The kidneys also produce hormones that help strengthen bones, control blood pressure, and direct the production of red blood cells. The filtered waste, in the form of urine, drains from the kidneys to the bladder through the ureters, and is excreted from the bladder through the urethra.

Congenital anomalies are abnormal variations in the anatomy at birth that affect the function of the kidneys and the healthy excretion of urine from the body.

Types of congenital kidney and urinary tract anomaly

Anomalies can be found in each part of the urinary tract.

Anomalies of the kidneys

  • One kidney may be missing (renal agenesis).
  • One or both kidneys may be abnormally small (renal hypoplasia).
  • One or both kidneys may have formed abnormally (renal dysplasia).
  • The kidneys may be joined to form a single arched or horseshoe kidney.
  • The kidneys may be in the wrong position.
  • One or both kidneys may have fluid-filled cysts (polycystic kidney disease or multicystic kidney disease).

Anomalies of the ureters

Anomalies of the urethra

  • Extra flaps of tissue may develop in the urethra, slowing or blocking the flow of urine out of the bladder (urethral valves).

When the flow of urine from the kidneys is blocked or slowed, or when urine is able to flow backward to the kidney, urine can build up in the kidney and cause it to swell, a condition known as hydronephrosis. This is often the first sign of a kidney and urinary tract problem, as the enlarged kidney can be seen in routine prenatal ultrasound images.


A family history of kidney or urinary tract problems may increase the risk of a baby being born with one of these anomalies, but in most cases the cause of the anomaly is unknown.

Signs and symptoms

Congenital anomalies of the kidneys and urinary tract are most often detected in a prenatal ultrasound. When this happens, doctors monitor the pregnancy carefully for signs of insufficient amniotic fluid, as the fluid is made up primarily of urine produced by the baby.

If a kidney or urinary tract anomaly is not detected before birth in an ultrasound, signs of the problem in infancy or childhood may include:

  • Urinary tract infections (sometimes noticed as unexplained fevers)
  • Swollen belly (from the bladder not emptying)
  • Swelling of the hands or feet or in the face around the eyes
  • Nausea and vomiting
  • Loss of appetite
  • Unusual tiredness or lack of energy
  • Poor growth

Testing and diagnosis

When a kidney or urinary tract anomaly is detected before birth in a routine ultrasound, additional prenatal imaging may be done to more accurately assess the problem and understand the risk to the baby.

To ensure an accurate diagnosis, it is important to visit a fetal therapy center with a multidisciplinary team experienced in evaluating pregnancies affected by kidney or urinary tract anomalies. At Children's Hospital of Philadelphia, you and your unborn baby will be seen in our Richard D. Wood Jr. Center for Fetal Diagnosis and Treatment for a thorough prenatal evaluation to help determine the best course of treatment and any special care your baby may need before, during and after birth.

Depending on the severity of the problem as seen in imaging studies, additional tests are done in the days or weeks after birth. These tests may include:

  • Urine test to check for infection
  • Blood test to estimate the kidneys’ function (glomerular filtration rate or GRF)
  • Ultrasound, CT scan or MRI of the kidneys and urinary tract
  • Voiding cystourethrogram (VCUG) — an imaging test using X-rays and marker material or dye to see how urine is flowing into and out of the bladder
  • Renal scan — a nuclear imaging test to assess kidney function and the drainage of urine

If the problem is not detected at birth, but is found later in childhood, additional tests may be done to understand the condition of the kidneys and assess possible loss of kidney function. These tests may include:

  • Blood test to estimate the kidneys’ function (glomerular filtration rate or GRF)
  • Blood tests to look for low red blood cells (anemia) or electrolyte abnormalities
  • Urine test to check for the presence of protein
  • Kidney biopsy


In some cases, no treatment is required. Children often outgrow minor problems with urine flow through the ureters and urethra. Even when one kidney is missing or damaged, no treatment may be needed. People can live healthy lives with partial kidney function or a single kidney.

In other cases, treatment ranging from medication to surgery may be needed to maintain health.

When vesicoureteral reflux is found, treatment may include:

  • Antibiotics to prevent urinary tract infections, which, with urine backflow, might otherwise spread to the kidneys and the bloodstream
  • Surgery to reattach the ureter to the bladder, creating an opening that closes when the bladder is full, or other procedures to help prevent reflux

In cases of severe ureter or urethra blockage, treatment may include:

  • Surgery to remove the blockage

When congenital anomalies of the kidneys and urinary tract are not detected early, or in cases when treatment is unable to prevent serious damage to the kidneys, kidney failure may require treatment with:


Minor congenital anomalies of the kidneys and urinary tract may not need treatment. When treatment is required, it is sometimes successful in correcting the problem and stopping further kidney damage.

When minor kidney damage occurs, it does not usually affect a person’s health or future life.

When kidney function falls to levels that cause serious health problems, dialysis and kidney transplantation can restore health.

Follow-up care

Children with congenital anomalies of the kidneys and urinary tract typically require monitoring through childhood and adolescence to periodically measure kidney function. If both kidneys are damaged, patients may need ongoing treatment to maintain health.

The frequency of that ongoing care and monitoring will vary greatly case by case.

Why choose CHOP?

The Division of Nephrology at Children's Hospital of Philadelphia (CHOP) provides your child with world-class care for and treatment of chronic kidney disease. Our division is consistently ranked as one of the top programs in the nation by U.S. News & World Report. Our physicians and staff are known for their ability to diagnose, treat and care for children with all forms of kidney disease, including congenital anomalies of the kidneys and urinary tract. Here, you'll find superb clinical care and an equal measure of understanding and compassion.

Our multidisciplinary team — including nephrologists, clinical nurse specialists, social workers, a pharmacist, psychologist, and nutritionist — provides comprehensive medical consultations and evaluations for children with renal diseases, electrolyte disorders and hypertension. We manage the care of children needing dialysis or a transplantation and work closely with other physicians at CHOP including neonatology, urology and transplant surgery to provide the best possible outcomes for our patients.

Reviewed by Benjamin L. Laskin, MD, MS

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