A child develops low-grade fever, lethargy, poor appetite, and abdominal discomfort several weeks after open-heart surgery. Which diagnosis from the material should be considered?

The described timing and symptoms suggest **postpericardiotomy syndrome**, a nonspecific hypersensitivity reaction to trauma involving the pericardium and epicardial surface of the heart. The lecture advises a high index of suspicion for an acute illness occurring within the first four to six weeks after cardiac surgery, although it notes that timing can be later. Low-grade fever, lethargy, loss of appetite, and abdominal pain may occur; chest pain may be absent. **Key takeaway:** Consider postpericardiotomy syndrome when compatible symptoms arise after cardiac surgery. **Glossary:** **Postpericardiotomy**: occurring after an incision into the pericardium during cardiac surgery. **Hypersensitivity reaction**: an exaggerated immune response.