This is a medical question of type : exams and tests 
 How to diagnose Biliary Atresia ? 
 No single test can definitively diagnose biliary atresia, so a series of tests is needed. All infants who still have jaundice 2 to 3 weeks after birth, or who have gray or white stools after 2 weeks of birth, should be checked for liver damage.2
                
Infants with suspected liver damage are usually referred to a
                
- pediatric gastroenterologist, a doctor who specializes in childrens digestive diseases  - pediatric hepatologist, a doctor who specializes in childrens liver diseases  - pediatric surgeon, a doctor who specializes in operating on childrens livers and bile ducts
                
The health care provider may order some or all of the following tests to diagnose biliary atresia and rule out other causes of liver problems. If biliary atresia is still suspected after testing, the next step is diagnostic surgery for confirmation.
                
Blood test. A blood test involves drawing blood at a health care providers office or commercial facility and sending the sample to a lab for analysis. High levels of bilirubin in the blood can indicate blocked bile ducts.
                
Abdominal x rays. An x ray is a picture created by using radiation and recorded on film or on a computer. The amount of radiation used is small. An x ray is performed at a hospital or outpatient center by an x-ray technician, and the images are interpreted by a radiologista doctor who specializes in medical imaging. Anesthesia is not needed, but sedation may be used to keep infants still. The infant will lie on a table during the x ray. The x-ray machine is positioned over the abdominal area. Abdominal x rays are used to check for an enlarged liver and spleen.
                
Ultrasound. Ultrasound uses a device, called a transducer, that bounces safe, painless sound waves off organs to create an image of their structure. The procedure is performed in a health care providers office, outpatient center, or hospital by a specially trained technician, and the images are interpreted a radiologist. Anesthesia is not needed, but sedation may be used to keep the infant still. The images can show whether the liver or bile ducts are enlarged and whether tumors or cysts are blocking the flow of bile. An ultrasound cannot be used to diagnose biliary atresia, but it does help rule out other common causes of jaundice.
                
Liver scans. Liver scans are special x rays that use chemicals to create an image of the liver and bile ducts. Liver scans are performed at a hospital or outpatient facility, usually by a nuclear medicine technician. The infant will usually receive general anesthesia or be sedated before the procedure. Hepatobiliary iminodiacetic acid scanning, a type of liver scan, uses injected radioactive dye to trace the path of bile in the body. The test can show if and where bile flow is blocked. Blockage is likely to be caused by biliary atresia.
                
Liver biopsy. A biopsy is a procedure that involves taking a piece of liver tissue for examination with a microscope. The biopsy is performed by a health care provider in a hospital with light sedation and local anesthetic. The health care provider uses imaging techniques such as ultrasound or a computerized tomography scan to guide the biopsy needle into the liver. The liver tissue is examined in a lab by a pathologista doctor who specializes in diagnosing diseases. A liver biopsy can show whether biliary atresia is likely. A biopsy can also help rule out other liver problems, such as hepatitisan irritation of the liver that sometimes causes permanent damage.
                
Diagnostic surgery. During diagnostic surgery, a pediatric surgeon makes an incision, or cut, in the abdomen to directly examine the liver and bile ducts. If the surgeon confirms that biliary atresia is the problem, a Kasai procedure will usually be performed immediately. Diagnostic surgery and the Kasai procedure are performed at a hospital or outpatient facility; the infant will be under general anesthesia during surgery.