Which of the following features is associated with acute biliary atresia?

Acute biliary atresia is characterized by a progressive obstruction of the bile ducts, which leads to the accumulation of bile in the liver. This condition often manifests within the first few weeks of life. One of the hallmark features of biliary atresia is cholestasis, which can lead to dark urine. The dark urine results from the excretion of conjugated bilirubin in the urine, a consequence of impaired bile flow.

In contrast, the other options do not directly correlate with acute biliary atresia in the same way. Splenomegaly may be seen in various liver conditions but is not specific to biliary atresia; it usually indicates portal hypertension or other chronic liver issues. Recent vaccination history is unrelated to biliary atresia and would not contribute to its diagnosis or presentation. Abdominal pain is not typically a feature of biliary atresia, as the condition is more characterized by signs of liver dysfunction and jaundice than by pain.

Thus, the presence of dark urine strongly indicates a problem with bilirubin processing, confirming the connection with acute biliary atresia.