For a 6-week-old breast-fed baby with jaundice and increased direct bilirubin, what is the most appropriate next step in management?

• A. Complete blood count
• B. Ultrasound of the abdomen
• C. Liver function tests
• D. Referral to a specialist

Answer: (B)

In the case of a 6-week-old breast-fed baby presenting with jaundice and increased direct bilirubin, the most appropriate next step in management is an abdominal ultrasound. This imaging test plays a crucial role in assessing for potential structural causes of jaundice, especially concerning biliary obstruction or anatomical abnormalities in the liver and biliary tree.

Increased direct bilirubin typically indicates conjugated hyperbilirubinemia, which can result from conditions such as biliary atresia or other liver disorders. An abdominal ultrasound is non-invasive and can help visualize the liver, gallbladder, and biliary tree to identify any obstructions or abnormalities that might be leading to the increased direct bilirubin levels.

While other options like liver function tests or complete blood counts can provide additional information, they are not as immediately helpful in ruling out anatomical causes of jaundice. Referral to a specialist may be necessary later depending on the findings, but it is essential first to assess the anatomical structure via ultrasound to guide further management.

Therefore, an abdominal ultrasound is the most appropriate next step to take in this clinical scenario.