Case Presentation: A 59-year-old man with a history of a chronic provoked bilateral pulmonary embolism with left lower extremity deep vein thrombosis (DVT), Non-ST-elevation myocardial infarction and hypercholesterolemia presented to the emergency department with acute, severe, constant left calf pain and swelling, exacerbated by standing. He stated that “I think I have another blood clot in my leg” and reported adherence to twice daily apixaban. He denied fever, trauma, recent travel or tobacco exposure. Physical examination revealed an uncomfortable-appearing patient in significant distress, due to pain. His temperature was 36.4C; pulse, 66/min; and blood pressure, 165/96 mm Hg. The left calf was swollen, moderately tender to palpation without significant erythema or warmth, with intact sensation. Popliteal and dorsalis pedis pulses were palpable. The remainder of the physical exam was unremarkable. Laboratory data revealed a normocytic anemia without leukocytosis with a normal activated partial thromboplastin time. Lower extremity duplex revealed a non-occlusive residual thrombus with partial vein wall compression with a 4.3 x 3.2 cm avascular mass of the proximal left calf, thought to be due to a DVT or possibly a Baker’s cyst. The patient was started on a heparin infusion for suspected acute on chronic left lower extremity DVT. A run-off computed tomography angiogram (CTA) of the left lower extremity revealed a large intramuscular hematoma within the left medial gastrocnemius with venous compression, distended subcutaneous venous collaterals and diffuse subcutaneous edema. Heparin infusion was discontinued and following negative evaluation by orthopaedic surgery for compartment syndrome, the patient was managed with oral analgesia, ice and elevation. Anticoagulation was held pending outpatient hematology evaluation for bleeding diathesis which ultimately revealed normal von Willebrand Factor antigen, ristocetin cofactor, factor VIII and platelet aggregation.

Discussion: Spontaneous calf hematoma is rare with the majority of cases reported in middle-aged or elderly males with no clear identifiable cause. In our patient’s case, the use of direct oral anticoagulation (DOAC) was determined to be the precipitating factor. The differential for unilateral calf pain and swelling is broad and should include etiologies such as DVT, hematoma, infection, and muscle rupture. A careful history and physical exam that includes use of antiplatelets or anticoagulants is vital to diagnosis. In this patient, the initial diagnosis was an acute on chronic DVT and the patient was treated with heparin infusion prior to confirmatory imaging which potentially could have resulted in limb-threatening complications. Lower extremity duplex lacked the specificity to distinguish between DVT, hematoma and a Baker’s cyst. CTA was pivotal in making the diagnosis of intramuscular hematoma and altered medical management through discontinuation of heparin infusion.

Conclusions: This case highlights the crucial importance of confirmatory imaging in the management of patients presenting to the hospital with unilateral calf swelling, particular in the setting of pre-existing lower extremity DVT. Run-off computed tomography angiogram (CTA) or Magnetic resonance imaging (MRI) are the imaging modalities of choice to identify the source, location and extent of bleeding. Surgical management may also be considered when clinically indicated, particularly in the setting of compartment syndrome.