Pulmonary emboli (PE) are a common clinical problem seen when a peripheral deep vein thrombosis (DVT) migrates to the pulmonary arteries. However, emerging literature suggests that not all filling defects in the pulmonary arteries are the result of embolism, and that in situ pulmonary arterial thrombus (ISPAT) or low-flow stasis artifact (LFSA) within the pulmonary arteries can mimic acute PE.