RADIOLOGY: VASCULAR: Case# 33936: RIGHT ATRIAL THROMBUS; ALVEOLITIS. 62 year old male with fever of unknown etiology. 1. Right atrial thrombus of unknown etiology. There is no thrombus in the IVC to suggest direct extension. 2. Alveolitis of unknown etiology. Differential considerations include extrinsic allergic alveolitis, CMV and ARDS. 3. No evidence of pulmonary embolus from right atrial thrombus.