Final answer:
A widened mediastinum on CXR and pericardial fluid post-cardiac surgery may suggest cardiac tamponade, a condition where fluid in the pericardial cavity compresses the heart, necessitating immediate medical intervention.
Step-by-step explanation:
The condition that presents with a widened mediastinum on chest X-ray (CXR) and a small amount of pericardial fluid on echocardiogram (echo), particularly following cardiac surgery, could indicate a postoperative complication such as cardiac tamponade. Cardiac tamponade occurs when excess fluid accumulates within the pericardial cavity, exerting pressure on the heart and compromising its function. This rare but serious condition requires prompt treatment, commonly the insertion of drainage tubes into the pericardial cavity to remove the excess fluid. Potential causes for this accumulation post-surgery include premature removal of drainage tubes or clot formation within these tubes.