The spleen is an organ inside the belly that helps filter blood. A splenic cyst is a fluid-filled structure in the spleen of the baby. They are often small and almost always cause no problems in the baby. Occasionally, they are large and can press other nearby organs.
A splenic cyst can be detected by ultrasound. They are usually found in the last 3 months of pregnancy. They are rarely present at the time of the anatomy scan around 20 weeks of pregnancy. They are seen as small, round areas within the spleen of the baby.
We don’t know why some babies have splenic cysts. Some experts suggest that there are changes in cells within the spleen that result in a small fluid collection. This has not been proven because most babies born with splenic cysts do not need to have them surgically removed, so the cyst are usually not looked at under a microscope.
You may be offered a more detailed ultrasound by a specialist. This is to carefully look at your baby for any other ultrasound findings or anomalies and to make sure that the cyst is located within the spleen and to help determine the cause for the cyst. Ultrasound can identify many but not all anomalies.
Additional ultrasound exams will usually be offered. These are done to monitor the growth of the baby and the size of the cyst. Some cysts actually disappear during pregnancy, while others may grow. If the cyst grows larger, ultrasound can be used to see if there is compression of any other nearby organs like the stomach and the left kidney.
If the cyst remains small, your baby will likely be healthy at birth. The baby will most likely have an ultrasound after being born to evaluate the size and location of the cyst. You will also likely be offered to have follow-up with a pediatrician to make sure the cyst doesn’t grow. Typically, these cysts do not need treatment unless the baby develops symptoms, which is quite rare.
Splenic cysts are unlikely to be seen in the next pregnancy.
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Last updated January 2021