What is the most likely diagnosis for a 3-week-old infant who presents with light tan-colored stools, worsening jaundice, and elevated direct bilirubin?

The presentation of a 3-week-old infant with light tan-colored stools, worsening jaundice, and elevated direct bilirubin strongly suggests biliary atresia as the most likely diagnosis. Biliary atresia is a condition characterized by the absence or obstruction of the bile ducts, which prevents bile from reaching the intestines. This leads to the characteristic pale stools, as the bilirubin, which normally colors the stool, is unable to reach the intestines. The accumulation of direct bilirubin in the bloodstream results in jaundice, further indicating a problem with bile excretion.

In this case, the infant's symptoms fit the classic signs of biliary atresia, where the obstruction of bile flow leads to the distinct stool color and the elevated direct bilirubin levels seen in cholestasis. Early recognition and diagnosis are crucial, as timely surgical intervention can significantly improve outcomes for the infant. Other conditions, while they may cause jaundice, do not typically present with the specific combination of pale stools and elevated direct bilirubin levels seen in this case.