Kidney cysts are round pouches of fluid that form in the kidneys and are typically less than 1 inch in diameter. The simple kidney cyst is different from the cysts that develop when a person has polycystic kidney disease (PKD), a genetic disease.
Simple Kidney Cysts
Simple kidney cysts are often detected during an
imaging test (e.g. ultrasound, CT, MRI) being done for another condition, because they rarely cause pain or other symptoms. It is not clear what causes simple kidney cysts, although the risk of having one increases with age. Simple kidney cysts in children are rare.
Complex Kidney Cysts
While cysts are commonly a simple sack of fluid, they can have multiple chambers, like a bag of grapes. These cysts are called complex, or septated, cysts. Septations are walls within the cyst. Having many or thick walled septations suggests a low but possible
cancer risk. If the cyst is complex,
your doctor may repeat the imaging test a few months later to be sure it is not growing and becoming cancerous.
Multicystic Dysplastic Kidney
Multicystic dysplastic kidney (MCDK) is a condition that occurs when a kidney is not put together correctly when it forms in the womb. The result is a non-functioning kidney full of cysts and scar tissue. Fortunately, the remaining kidney is usually able to take over all kidney function. In infants with MCDK, however, the remaining kidney may have an abnormality. Your doctor may do more tests to evaluate this kidney.
Incidence: MCDK affects 1 in every 4,000 babies.
Diagnosis: 70% of MCDK cases are diagnosed by
ultrasound before a baby is born.
Prevention: There is no way to prevent MCDK from occurring early in a baby's development, and there is no known way to prevent it from happening later in life.
Outlook: A baby with MCDK and no other birth defects has a normal life expectancy. For
a child with only one kidney that works, that kidney may be a little bigger than normal. She will need follow-up care for life to make sure the kidney remains healthy.
Polycystic Kidney Disease
Kidney cysts can also be caused by a
genetic mutation. The most common form of this is PKD, in which cysts can replace the kidney over time and cause kidney failure. There are two forms: autosomal dominant (ADPKD) and autosomal recessive (ARPKD).
Autosomal Dominant Polycystic Kidney Disease
Large kidney cysts are associated with ADPKD. They often begin to appear in childhood, although most affected children and teens have no symptoms until they are adults.
Incidence: ADPKD affects 1 in 500. It does not skip a generation. There is usually a family history of ADPKD. A parent with ADPKD has a 50% chance of passing the disease on to each of their children.
Symptoms: Often the first sign is
high blood pressure,
blood in the urine, or a feeling of heaviness or pain in the back, sides, or abdomen. Sometimes, the first sign is a
urinary tract infection (UTI) and or
Children with a family history of ADPKD should have periodic urinalyses and blood pressure measurements to identify early manifestations of the disease. It is
not recommended for otherwise healthy children and teens to have kidney-imaging tests done, regardless of whether a parent has ADPKD. One reason is that it may adversely affect the child’s insurability, even if there are no symptoms yet. Routine genetic testing of potentially affected children and teens is also
Note: These recommendations may change with advances in the treatment of ADPKD.
Outlook: There is currently no accepted therapy to prevent cysts from forming or enlarging.
Autosomal Recessive Polycystic Kidney Disease
Enlarged kidneys with tiny cysts are associated with ARPDK. Sometimes, the kidneys are so large and function so poorly that infants are born with
severe respiratory problems and do not survive.
Incidence: ARPKD is relatively rare and occurs in 1 in 20,000.
Diagnosis: Most ARPKD cases are diagnosed by ultrasound before a baby is born.
Outlook: Most children with ARPKD have high blood pressure and progressive kidney failure. They will need to be on kidney dialysis and or receive a kidney
transplant by late childhood to survive. A number of these children will also develop liver disease, leading to esophageal bleeding and ultimately liver failure.
Physical Activity & Children with Cystic Kidney Disease
Very large cysts can rupture with minor trauma and lead to blood in the urine and occasionally severe hemorrhaging.
Your child's doctor will help decide if physical activity should be limited. It is possible that children with large kidneys and/or large cysts will have more episodes of blood in the urine if they play contact sports, such as
Outlook for Children with Kidney Cysts
The number of cysts a child has affects his signs and symptoms. In most children, kidney cysts grow very slowly, if at all, and cause no problems. Therefore, there is no treatment needed.
If a cyst becomes very large, it may cause
side or stomach pain or interfere with the kidney's function. However, it is extremely rare to do surgery on a cyst. Typically, a cyst is removed or drained if it is infected and not responding well to antibiotics or is causing significant pain. A
pediatric nephrologist and a
pediatric urologist work together to decide whether to remove kidney cysts.
Note: Surgery can only remove a limited number of cysts in children with cystic kidney disease. After surgery, the smaller cysts can continue to enlarge. This means the surgery is not the final treatment and further care is needed for long-term management.