Chronic Post-Traumatic Organized Hematoma of the Brachial Artery: The Role of Multimodal Ultrasound

Chronic post-traumatic organized hematoma of the upper extremity is uncommon and may mimic a soft-tissue mass or a pseudoaneurysm when predominantly thrombosed. We report a 60-year-old woman with progressive right upper-arm swelling and finger numbness 30 years after blunt trauma. CT angiography demonstrated a low-attenuation mass along the brachial–ulnar arterial course with tortuous vessels along its margin. Gray-scale ultrasound demonstrated a large heterogeneous, predominantly hypoechoic lesion adjacent to the brachial artery, while conventional color Doppler provided limited vascular information. Superb microvascular imaging (SMI) detected sparse intralesional and perilesional arterial flow, and contrast-enhanced ultrasound (CEUS) further demonstrated partial microbubble filling supplied by small arterial branches arising from the brachial artery. These findings initially raised the possibility of a chronic partially thrombosed pseudoaneurysm; however, no pseudoaneurysmal neck or characteristic to-and-fro flow was identified. The lesion was therefore considered most consistent with a chronic post-traumatic organized hematoma with neovascularization supplied by small brachial artery branches. Ultrasound-guided biopsy revealed organized fibrous tissue with hemorrhage and sparse inflammatory cells, supporting an organizing hematoma and excluding malignancy. This case underscores the diagnostic challenge of chronic post-traumatic organized hematoma and highlights the role of comprehensive ultrasound, particularly SMI and CEUS, in characterizing vascularity and informing clinical decisions.