Depending on the exact issues involved, someone with CAKUT might have a condition that only causes symptoms later in life. On the other hand, a more serious problem could cause a life-threatening issue from infancy.
Although many people are more familiar with other kinds of congenital abnormalities (like congenital heart issues), congenital abnormalities of the kidney and urinary tract are the most common kind of congenital birth defect, affecting roughly 1 in 500 babies born.
Some type of CAKUT is the cause in roughly half of children who have end-stage kidney disease. In adults with end-stage kidney disease, CAKUT accounts for about 7% of cases.
Types of CAKUT
Many different types of CAKUT exist, which can be categorized in different ways based on the specific organ affected, the type of involvement, and the different genetics involved (if known). In some cases, multiple parts of the urinary tract are affected. The issues could affect both sides of the body or only one side.
CAKUT can include one or more of the following:
Abnormally shaped or positioned kidney (e. g. , a “horseshoe kidney”) Partial kidney duplication Renal agenesis (complete failure of one or both kidneys to form) Kidney dysplasia (disordered kidney development) Kidney hypoplasia (small kidneys) Reflux of urine into the kidneys Problems with the urethra valves (such as posterior valves) Extra ureter or enlarged ureter Failure of the urethra to form Bladder anomalies, including bladder enlargement Obstruction (where the ureter connects to the kidney or the bladder)
CAKUT can also be a part of medical syndromes that affect multiple bodily systems. These include renal-coloboma syndrome, orofaciodigital syndrome, renal cysts, diabetes syndrome, Fraser syndrome, VACTERL syndrome, and many others.
Sometimes, other heritable forms of kidney disease are grouped along with CAKUT. For example, autosomal dominant polycystic kidney disease and autosomal recessive polycystic disease are two different inherited diseases that cause fluid-filled cysts to form inside the kidneys.
These cysts eventually interrupt kidney function and cause symptoms. However, some healthcare providers don’t include them when talking about CAKUT.
CAKUT Symptoms
The symptoms from CAKUT will depend somewhat on the specific type of congenital problem and its severity, as well as on a person’s age. Potential issues include:
Distended belly due to bladder enlargement Difficulty feeding and poor weight gain in infants Increased urinary tract infections Profuse or decreased urination Electrolyte disturbances Delayed puberty Decreased height Anemia High blood pressure Cardiovascular disease
Additionally, some fetuses with very poor kidney function will have low amniotic fluid while in the womb (oligohydramnios). This is an issue because the prenatal kidneys normally produce this fluid. This can cause other problems, like reduced growth, delayed lung maturation, limb defects, and sometimes death.
If CAKUT causes major damage to the kidneys, this can eventually cause symptoms of renal failure. If not treated with kidney transplant or hemodialysis, this can cause life-threatening problems such as the inability to make urine, severe electrolyte problems, neurological issues, increased tendency to bleed, and extremely high blood pressure. In severe cases, end-stage renal disease happens in the first years of life.
Some, but not all, people with CAKUT have problems with other body systems that might lead to additional symptoms. For example, some people with congenital problems affecting the kidney or lower urinary tract also have problems with the development of the heart, lungs, nervous system, or other organs.
Causes
Abnormal Anatomical Development
The prenatal development of the urinary system requires a complex series of physiological steps. These must be carefully coordinated as the different cell types develop into what will become the organs of the urinary system. When something disrupts this developmental pathway, CAKUT can happen.
Most people understand that the kidneys make urine, which is then transported through the urinary tract, traveling from the kidneys through the ureter and then into the bladder. Next, it flows through the urethra and out of the body. Through this system, your body removes waste products via your urine.
But the urinary system provides several other important functions. For example, your kidneys help regulate the amount of fluid in your body, as well as the amount of certain electrolytes (salts) in your blood. They also plays a key role in blood pressure control. In addition, the kidney is important for utilizing vitamin D and for producing a hormone needed to make new red blood cells.
As a result, the potential symptoms caused by CAKUT relate to these normal functions. In some types of CAKUT, the urine can’t leave the body in the normal way because there is a blockage or restricted opening. In these cases, the urine can get backed up and lead to problems.
Depending on the specific problem, this can cause abnormal enlargement of the ureter, bladder, or kidney (hydronephrosis). If not corrected, this can permanently damage the kidney over time.
Genetic and Non-Genetic Causes
Some kinds of CAKUT are genetic in nature. A specific mutation in a gene causes the kidney (and perhaps other parts of the urinary system as well) to not form normally.
Researchers have identified mutations in several different genes that can cause CAKUT, two of which are PAX2 and BMP4. Researchers are still discovering new ones.
Different mutations can lead to specific types of CAKUT of varying severity and potential treatment options. In these cases, CAKUT can be passed down in families, although this is not always the case.
Sometimes CAKUT comes along with a chromosomal abnormality. For example, many people are familiar with trisomy 21, also known as Down syndrome, which occurs when a person has an extra copy of chromosome 21.
Some people with Down syndrome have CAKUT, as do some people with other types of chromosomal abnormalities, such as trisomy 18. In chromosomal abnormalities, however, CAKUT isn’t the only issue.
Other times a person is found to have a CAKUT even though no one else in the family has ever had one, and even though no genetic cause can be found.
Some environmental factors have been shown to increase the risk of CAKUT. Two of these are diabetes in the mother and exposure to ACE inhibitors (like captopril) prenatally. However, much of the time, no cause can be found.
Diagnosis
CAKUT is now often first diagnosed prenatally. This has become more common since it became the standard of care to perform comprehensive anatomical exams (using a special kind of ultrasound) during the second trimester of pregnancy.
However, this test isn’t perfect, and sometimes a fetus who is diagnosed with a potential CAKUT prenatally is born without any problems.
If there is a concern about CAKUT, it’s very helpful to get genetic counseling and care with a multi-disciplinary team. In some cases, genetic testing may be recommended to help get an idea of the exact nature of the problem. Your healthcare provider can give you an idea of the potential severity of the issue.
The medical history and exam are a crucial part of the diagnostic process. Your healthcare provider will ask about any symptoms and past medical problems.
It’s important to find out if anyone else in the family has had problems with their kidneys or with urinary tract disease. This can give helpful clues about the specific cause. It’s important to realize that even if a cause is genetic, it doesn’t mean that CAKUT will show up the same way in each individual in a family.
Basic tests can play a diagnostic role. For example, standard blood tests might include a complete blood count and blood markers used to measure kidney function. Basic urine tests are often helpful. Using some of these findings, healthcare providers can get an estimate of how well the kidneys seem to be functioning.
Imaging tests are critical for understanding the specific anatomy involved. These might include tests like the following:
Voiding cystourethrogram Ultrasound of the kidneys Diuretic renal scan (using injection of radioactive tracer material) Computerized tomography (CT) scans Magnetic resonance urography (performed in an MRI machine)
Treatment
Treatment is tailored based on the specific CAKUT and the individual clinical situation. These individuals will need ongoing monitoring, care, and treatment from healthcare practitioners experienced in these conditions.
Treating Kidney Issues
Many individuals with CAKUT and kidney problems will eventually have kidney failure. That means the kidneys no longer function well enough to remove waste, leading to death if not treated. To prevent this, a person needs ongoing dialysis treatments or a kidney transplant.
A kidney transplant is preferred, but a suitable kidney might not always be available. If so, someone with severe kidney disease may need to undergo dialysis until an appropriate donor kidney becomes available.
A kidney transplant should cure the underlying issue. However, post-surgery, the individual will need to take lifelong immunosuppressive medications.
It is helpful to delay the need for dialysis or a kidney transplant for as long as possible. One important way to do this is by making sure the blood pressure doesn’t get too high.
As a result, one or more medications to lower the blood pressure are frequently used, often medications like ACE inhibitors (like captopril) or ARBS (like losartan). This can help delay the need for kidney replacement therapies.
Other therapies can sometimes help with some of the other complications of kidney disease, such as growth hormone for decreased height or vitamin D supplements.
Treating Lower Urinary Tract Issues
For problems that affect the lower urinary tract, surgical repair may be possible, depending on the specific situation. For example, a surgery might be able to correct an abnormal urethral valve.
A procedure called a pyeloplasty might help surgically correct a kidney that has become enlarged, or surgery might help the urine flow normally from the ureter to the bladder. Other types of surgery may be needed in specific situations.
Outlook
Unfortunately, in some cases, treatment possibilities are limited. Babies born with renal agenesis of both kidneys usually die within a few days of birth. However, the prognosis is much better for most kinds of CAKUT.
For many types of CAKUT, kidney function improves for the first couple of years of life and then plateaus for a time, before kidney replacement therapy (dialysis or transplant) becomes necessary later in adolescence. Your healthcare provider can give you a better idea of the prognosis in your situation.
Dealing with the issues of CAKUT can take a psychological toll. It’s often helpful for both patients and caregivers to get emotional and psychological support from a trained professional.
Genetics and Inheritance
It’s key to get the help of a trained geneticist when dealing with CAKUT. This can be helpful in initial diagnosis as well as in estimating risks for other family members. This may include getting specialized types of blood tests to try to identify the specific gene or genes that might have been involved. It’s also helpful for family planning purposes.
Some types of CAKUT seem to be inherited in an autosomal dominant fashion. That means that someone with CAKUT would have a 50% chance of passing it down to a child (although the symptoms and issues might not be exactly the same).
Less commonly, CAKUT might be autosomal recessive, meaning that a person would need to inherit an affected gene from both of their parents to be affected (not just one). But much of the time, a gene can’t be identified, so an exact risk can’t be determined.
A Word From Verywell
CAKUT represents a diverse array of problems that cause the kidney or other parts of the urinary system to not develop properly. Though individually uncommon, as a group they affect a significant number of people.
There’s a lot to learn about the condition, but your treatment team will help you understand the details of your situation. Working with an interdisciplinary healthcare team will help you make the best treatment decisions for you.
