Biliary atresia is a serious liver disease in newborns where the bile ducts outside the liver become inflamed, scarred, and ultimately blocked. Without functioning bile ducts, bile cannot drain from the liver into the intestines, leading to liver damage that progresses to cirrhosis if untreated. It affects roughly 5 to 6 out of every 100,000 live births in Europe and North America, with significantly higher rates in East Asian countries and French Polynesia, where incidence ranges from 15 to 29 per 100,000.
How Biliary Atresia Damages the Liver
Bile is a digestive fluid produced by the liver. It travels through a network of small tubes called bile ducts, eventually reaching the intestines where it helps break down fats and absorb nutrients. In biliary atresia, the body’s own immune system attacks the cells lining these ducts. Immune cells swarm the area, creating inflammation that destroys the duct lining and forms a plug of scar tissue that blocks bile flow entirely.
Once bile can no longer drain, it backs up into the liver. This causes ongoing damage to liver cells, triggers more scarring (fibrosis), and eventually leads to cirrhosis. By the time a baby is diagnosed, the bile ducts outside the liver are completely obstructed. Inside the liver, the smaller ducts are typically overgrown and surrounded by inflammation and fibrosis. Without treatment, the progression to end-stage liver disease is consistent.
Recognizing the Signs
The earliest and most visible sign is jaundice, the yellowing of a baby’s skin and eyes. Many healthy newborns develop mild jaundice in the first week or two of life, so biliary atresia can be easy to miss initially. What sets it apart is that the jaundice doesn’t fade. It persists or worsens beyond two to three weeks of age.
Two other early clues are pale or white stools and unusually dark urine. Normal newborn stool has a yellow, green, or brown color because bile pigments pass through the intestines. When bile can’t reach the intestines, stools lose their color. Stool color cards, which help parents and healthcare providers compare their baby’s stool against normal and abnormal shades, have been shown to speed up the time to diagnosis. Despite these signs, babies with biliary atresia often appear healthy at first and may grow well in the early weeks. Later signs like poor weight gain, a swollen belly from fluid buildup, and an enlarged spleen typically don’t appear until after three months, when cirrhosis has already set in.
Isolated vs. Syndromic Forms
Most babies with biliary atresia have no other birth defects. This is the isolated form, and it accounts for the large majority of cases. In roughly 10% of cases in European and North American populations, biliary atresia occurs alongside a specific pattern of other anomalies known as biliary atresia splenic malformation syndrome (BASM). Babies with BASM typically have abnormalities of the spleen (often multiple small spleens instead of one), reversed organ positioning, absence of a major vein in the abdomen, and a portal vein that sits in front of the intestine instead of behind it.
Rarer syndromic forms have also been identified, including associations with Cat-Eye syndrome, Kabuki syndrome, and several others. Some otherwise isolated birth defects, like esophageal or intestinal blockages and cleft palate, appear alongside biliary atresia more often than chance would predict.
How It’s Diagnosed
Diagnosing biliary atresia involves a combination of imaging, tissue sampling, and sometimes surgery. An abdominal ultrasound is often the first test. Specific findings can raise suspicion: a missing gallbladder is highly specific for biliary atresia (100% specificity in some studies), and a “triangular cord” sign near the liver can point toward the diagnosis, though neither finding catches every case. A nuclear medicine scan can assess whether bile is flowing into the intestines at all.
A liver biopsy, taken through the skin with a needle, often shows a characteristic pattern of overgrown bile ducts and scarring in the liver’s portal areas. However, false positives and false negatives do occur, especially as the disease progresses and the biopsy appearance shifts.
The definitive diagnosis requires surgery. During an operative cholangiogram, a surgeon injects dye directly into the bile duct system to see whether any open passages remain. If no open ducts are found, the surgeon proceeds immediately with the corrective operation.
The Kasai Procedure
The primary surgical treatment is called a Kasai portoenterostomy. The surgeon removes the damaged, blocked bile ducts outside the liver and connects a loop of intestine directly to the liver’s surface, creating a new path for bile to drain. Timing is critical. About half of babies who undergo the Kasai procedure before two months of age will achieve enough bile flow to grow and remain healthy for years. Outcomes are noticeably better when surgery happens before 30 to 45 days of life, and they worsen significantly when it’s delayed past 90 days. The old benchmark of 60 days is not a sharp cutoff; rather, it’s a general window where earlier consistently outperforms later.
Even when the Kasai procedure restores bile flow, the liver damage already present does not fully reverse. Many children eventually develop progressive liver problems despite an initially successful surgery. Very rarely, a child with biliary atresia lives their entire life without needing further intervention.
Liver Transplantation
Biliary atresia is the leading reason for liver transplantation in children. By age five, approximately 37% of children with the condition have undergone a transplant, with the median age at transplant being just over 10 months. Some children need a transplant because the Kasai procedure didn’t restore enough bile flow; others do well for months or years before the liver deteriorates.
Outcomes after transplant are encouraging. In the United States, more than 90% of children are alive five years after receiving a new liver. Long-term data shows an 80% survival rate at 30 years post-transplant, meaning most children who receive a liver go on to live well into adulthood.
Nutritional Challenges After Diagnosis
Because bile is essential for absorbing dietary fat, babies with biliary atresia struggle to get enough calories and key nutrients even after surgery. Healthy infants need about 100 to 120 calories per kilogram of body weight each day. Babies with biliary atresia need 30 to 50% more, roughly 130 to 150 calories per kilogram, to support adequate growth.
Standard infant formula fats are difficult for these babies to absorb. Special formulas enriched with medium-chain triglycerides (MCTs), a type of fat that can be absorbed without bile, are a cornerstone of their nutrition. If specialized formula isn’t available, refined MCT oil can be added to standard formula. Essential fatty acids like omega-3 and omega-6, which are critical for brain and nervous system development, may need to be given in water-soluble or emulsified forms to improve absorption.
Fat-soluble vitamins (A, D, E, and K) are particularly hard for these babies to absorb, since they rely on bile for uptake. European pediatric nutrition guidelines recommend using water-soluble or specially formulated versions of these vitamins. Doses are often much higher than what a healthy infant would need and are adjusted based on regular blood monitoring. A bile acid replacement medication called ursodiol is sometimes used to help with both fat digestion and liver protection.