Congenital Abnormalities of the Kidneys and Urinary Tract (CAKUT)
Congenital anomalies of the kidneys and urinary tract (CAKUT) are one of the top causes of end stage renal disease (ERSD) in children. Explore what CAKUT are and potential treatments.
- Medically reviewed by
- Oliver Brooks MD
- Last updated
- August 8, 2024
What is CAKUT?
CAKUT is the abbreviation commonly used for congenital, or conditions that exist at birth, anomalies of the kidneys and urinary tract. This refers to a group of anomalies (abnormalities) that occur as a baby grows. Those who have CAKUT have one or more kidney or urinary tract abnormalities.
CAKUT are responsible for 40-50% of all pediatric end stage kidney disease cases.
Some examples of kidney abnormalities include:
- Changes in the size and location of the kidneys
- Abnormal growth and development that affects kidney function
- A kidney made up of cysts (small pocket filled with fluid)
- Blockages in the ureter (the tube that urine flows through from the kidneys to bladder) where it joins the kidney
- Underdevelopment of a kidney
- Buildup of urine in the kidney
- Having only one kidney
As the name implies, CAKUT also includes issues in the growth and development of the urinary tract. The urinary tract is your body's system that removes waste and extra fluid from the blood through urine (pee). This system includes:
- The kidneys
- Ureters (tubes that carry urine from the kidneys to the bladder)
- Bladder (hollow, balloon shaped organ that holds urine)
- Urethra (tube that urine uses to leave your body from the bladder)
Some examples of urinary tract abnormalities include:
- Urine building up in the bladder
- Extra or very wide ureters
- Urine that backflows into the bladder
- Abnormal membranes in the urethra which block urine from leaving the body
Who does CAKUT affect?
CAKUT happens during pregnancy, as the baby grows. A pregnant person will not have any symptoms of CAKUT, even if their baby is diagnosed with any of these abnormalities.
Kidneys in a growing baby can be seen on an ultrasound between weeks 12 and 15 of pregnancy. An ultrasound is an imaging test that uses sound waves to create images of things inside your body, including a baby if a person is pregnant. CAKUT are usually diagnosed between weeks 16 and 20 of pregnancy during a routine ultrasound, though some may not be found until later in life.
CAKUT occurs in about 45 of 10,000 babies born. They are more commonly diagnosed in male babies.
It is not completely understood why CAKUT occurs. Some factors believed to be involved include:
- Genetic mutations (change or variation in one or more genes)
- Maternal health (including maternal history of chronic kidney disease)
- Family history of CAKUT
- Diabetes (including gestational diabetes)
- Exposures to teratogenic medicines or medicines that cause birth defects, such as angiotensin-converting enzyme (ACE) inhibitors and some anti-seizure medicines, during pregnancy
More research is needed to understand how genetics affect CAKUT and how it may be inherited (passed on from family members).
What are the symptoms of CAKUT?
Many cases of CAKUT are diagnosed before a baby is born through imaging tests, such as ultrasounds.
For children diagnosed after birth, the most common symptom is frequent urinary tract infections (UTIs). UTI's can spread to the kidneys and cause kidney damage. If your child has frequent UTI's talk to their doctors about why this may be occurring so frequently, and if they should be examined for CAKUT.
Symptoms of a UTI in children can include:
- Needing to urinate (pee), even after you have already peed
- Peeing in small amounts often
- Red, pink, or cola-colored pee
- A strong smell coming from pee
- Pain above the pubic bone
- Pain in the back or side below the ribs
- Wetting themselves during the day or night (after being fully potty trained)
- Nausea and vomiting
- Tiredness
- Fever and chills
For infants, symptoms can also include:
- Crying while peeing
- A strong, foul smell coming from pee
- Fever
- Nausea or vomiting
- Weight loss
- Diarrhea
How are CAKUT diagnosed?
CAKUT are usually diagnosed during pregnancy, typically when the baby is between 16 and 20 weeks old. During this time, many of the baby's organs are growing, including their kidneys. This makes it a good time for doctors to look for CAKUT on ultrasounds.
If a full bladder can be detected in the baby, this is an indicator that at least one kidney is functional. The function of an unborn baby's kidneys can also be tested by looking at the amniotic fluid, which is the fluid in the womb that surrounds and protects a baby during the pregnancy. The amount of fluid and the chemicals in the fluid can help doctors diagnose CAKUT.
The ureters of an unborn baby are not usually seen on an ultrasound. If they are, it can indicate a blockage in the ureter or bladder, or vesicoureteral reflex (VUR), all of which are kinds CAKUT. VUR is when urine flows backward from the bladder to the ureter and sometimes the kidneys.
Once a baby with suspected CAKUT is born, doctors will do the following tests to gather more details on the baby's condition:
- Imaging: Ultrasounds and CT scans may be done to visualize the kidneys and other structures, and to search for blockages.
- Blood tests: blood tests may be done to measure kidney function. This may occur within a day or more after birth to ensure kidney function is being accurately assessed.
- Physical Exam: physical exams can help find any masses that could be an enlarged kidney or a full bladder, both of which can indicate blockages.
Doctors may suspect CAKUT in male infants with prune belly syndrome, a birth defect that causes the skin on a baby's belly to wrinkle, and infants with single umbilical cord arteries.
For children with frequent UTI's who have not already been diagnosed with CAKUT, these tests along with urine testing, can help confirm a diagnosis.
How are CAKUT treated?
Treatment of CAKUT depends on the severity, which can range from mild to severe.
Mild cases include frequent UTIs and blockages in the urinary track. Repeated UTIs are important to treat, as overtime, frequent UTI's can damage the kidneys and the bladder. Blockages anywhere in the urinary tract should be treated as well. In children, blockages are often caused by structural issues. While these instances of CAKUT may not be categorized as severe, they are still dangerous.
Treatment strategies for mild cases of CAKUT can include:
- Teaching children different positions to use when urinating or voiding (pooping)
- Taking a daily medicine
- Catheterizing the urinary tract (this is when doctors insert a flexible tube into the bladder to drain urine)
- Interventions while the baby is still inside the womb
- Surgery (once a child is old enough)
Severe forms, such as the absence of a kidney or a malformed kidney, can result in chronic kidney disease (CKD) and kidney failure. For children who progress to this stage, transplant is the most successful intervention. For those whose transplants are not immediately available, dialysis is another treatment option.
Pediatric kidney disease can be progressive, so as children with CAKUT get older, their primary care providers should closely monitor their kidney function with certain lab tests like their eGFR, cystatin C, and serum creatinine. Growth failure in children with CKD is common, it's important to work with your child's medical provider to watch for any CKD related stunted growth.
Can I Prevent CAKUT?
Preventing CAKUT is difficult because the causes are not completely understood. Generally, pregnant people should do their best to avoid any medicines or substances that can harm the baby, attend all doctors' appointments, and maintain a healthy lifestyle.
If you have a family history of CAKUT, have CKD, or diabetes, work with your doctor to understand the risks and plan for your pregnancy.
