Descripción general
Biliary atresia is a rare liver condition that affects newborns and infants. It occurs when the bile ducts become inflamed and blocked or fail to form correctly. Bile ducts are slender tubes that carry the digestive fluid bile from the liver to the small intestine. When bile cannot flow out of the liver, it builds up and causes liver damage, scarring and, eventually, progressive and severe scarring known as cirrhosis.
Biliary atresia appears in about 1 in every 10,000 to 20,000 live births, making it the leading cause of liver transplants in children. Babies with biliary atresia usually appear healthy at birth. The first sign of illness is often yellowing of the eyes and skin, called jaundice, and pale stools that last beyond two weeks.
Babies with biliary atresia should undergo a surgery called Kasai surgery. It also is called hepatoportoenterostomy. This procedure helps relieve bile buildup and slow liver damage, but it does not cure the condition. The surgery works best when done early in life, ideally within the first 60 days. The earlier it is performed, the better the outcome.
Although many children eventually require a liver transplant, a successful Kasai surgery can delay this need for many years. Some individuals may reach adulthood without ever needing a liver transplant.
Types
Healthcare professionals sometimes describe biliary atresia as either syndromic or nonsyndromic, depending on whether other birth defects are present.
- Syndromic biliary atresia. In some babies, biliary atresia occurs along with other structural problems, such as heart defects, spleen problems or differences in how the intestines are arranged. These babies may need extra tests and specialized care for those conditions.
- Nonsyndromic biliary atresia. In most cases, biliary atresia occurs without other malformations.
Healthcare professionals classify biliary atresia using the Kasai classification, which describes where the bile ducts are blocked:
- Type 1. The main bile duct, also called the common bile duct, is blocked. But the ducts inside the liver are still open.
- Type 2. The blockage is higher up, where the right and left bile ducts come together. But the smaller ducts inside the liver are still open.
- Type 3. Blockage is at the duct where bile leaves the liver, called the porta hepatis, with complete blockage of the extrahepatic biliary tree. This is the most common and severe form.
Understanding the type of biliary atresia helps healthcare professionals decide what approach may offer the best outcome.
Síntomas
Symptoms of biliary atresia usually appear during the first few weeks of life. Most babies appear healthy at birth. But as bile becomes trapped in the liver, signs of illness gradually appear. Symptoms usually appear between ages 2 and 8 weeks.
Common symptoms of biliary atresia include:
- Jaundice that lasts longer than two weeks after birth. This is one of the earliest and most reliable warning signs. Unlike typical newborn jaundice, which fades as the baby's liver matures, the jaundice seen in biliary atresia is a different type caused by bile not draining properly from the liver. It does not improve and may deepen in color.
- Pale, gray or white stools. Bile gives stool its typical brown color, so when bile flow is blocked, stools become light or clay colored. Parents often describe them as "putty colored."
- Dark yellow urine. Because bilirubin builds up in the blood, it passes into the urine, giving it a dark or tealike appearance.
- Swollen belly or firm liver. If biliary atresia is not detected early and the Kasai surgery is not performed in time, the liver and spleen may become enlarged.
- Poor weight gain or irritability. As liver function declines, babies may feed poorly or fail to gain weight.
How is biliary atresia different from infant jaundice?
Typical newborn jaundice is caused by a temporary buildup of bilirubin and resolves on its own. But jaundice from biliary atresia results from blocked bile ducts and ongoing liver injury. Persistent yellowing of the skin and eyes, pale stools, and dark urine should always prompt medical evaluation. Because many healthy babies also have mild jaundice early in life, recognizing when it persists or worsens is critical.
Causas
Scientists don't yet know exactly what causes biliary atresia, but research shows it likely begins before the baby is born. There is no evidence that biliary atresia is inherited or caused by anything a parent did or didn't do during pregnancy. It also isn't something a child with biliary atresia will pass on to their own children.
Researchers believe biliary atresia may be triggered by a mix of factors. These include problems with how the bile ducts form during pregnancy, certain genes, and possibly infections or toxins that affect the baby in the womb. The more-common type appears in healthy-looking babies during the first few weeks of life. A less common type happens alongside other birth defects, such as heart or spleen problems. This less common type is called embryonic biliary atresia. It's also known as syndromic biliary atresia.
Factores de riesgo
There are no proven, consistent risk factors that predict which babies will develop biliary atresia. Most cases appear sporadically, meaning they happen by chance in otherwise healthy infants with no family history or known cause.