Diagnosis and Treatment Approach for Giant Muscle Hematoma of the Thigh Due to a Post-traumatic Arteriovenous Fistula: A Case Report.

Intramuscular hematomas have varied etiologies, and accurate diagnosis requires a detailed medical history in combination with laboratory and imaging evaluations. We report a case of a giant thigh hematoma that enlarged over a chronic course and was ultimately attributed to a post-traumatic arteriovenous fistula (AVF). An 18-year-old man was diagnosed with an intramuscular hematoma after blunt trauma to the thigh, which gradually enlarged. He later presented with sudden worsening of thigh swelling and pain and was transported to the emergency department. Contrast-enhanced CT showed extravasation in the proximal thigh together with dilation of the internal iliac and inferior gluteal arteries, raising suspicion of a vascular malformation. Angiography performed the same day confirmed active bleeding from an AVF at the level of the inferior gluteal artery. Because surgical hemostasis was deemed difficult, transcatheter arterial embolization (TAE) was performed, and achieved hemostasis. Three months later, with no recurrence of abnormal vessels, the giant hematoma was excised. The patient has remained free of recurrence for five years. When encountering a large intramuscular hematoma, clinicians should consider a high-flow vascular malformation. Identification of signal voids on MRI and extravasation on contrast-enhanced CT is critical for early diagnosis. For active bleeding due to high-flow lesions, arterial embolization is an effective therapeutic option.