Deep venous thrombosis seen on magnetic resonance imaging after ankle sprain.

A 49-yr-old woman with a work-related left-ankle sprain noted pain and bruising of her shin and medial ankle immediately after injury. She was treated for the ankle sprain with anti-inflammatory medication and reported gradual improvement. (Her only other medication was an oral estrogen/progesterone replacement therapy for menopausal symptoms.) Four weeks later, she developed increased calf pain and swelling. A lower limb venous duplex ultrasound revealed no thrombus. Radiographs of her left foot, ankle, tibia, and fibula were also normal. Four months after the initial injury, she presented for evaluation in the physical medicine and rehabilitation department with complaints of swelling and aching in her left leg. Pertinent positives on physical exam included antalgic gait, calf circumference discrepancy (left calf 1.5 cm greater in circumference than the right calf), minimal ankle tenderness, and severe proximal left thigh tenderness. The neuromuscular exam was otherwise unremarkable. The differential diagnoses included vascular compression, peripheral nerve injury, and radiculopathy. Although sonography has become an acceptable screening tool, contrast venography remains the gold standard when deep venous thrombosis (DVT) is suspected. Venography was not performed in this case because the authors’ clinical suspicion for DVT was quite low. Magnetic resonance imaging, which was obtained to evaluate the inguinal neurovascular structures, identified acute thrombosis of the common femoral vein, with an intense soft-tissue inflammatory reaction. There was no evidence of cephalic extension, but caudal extension was likely present based on the extensive surrounding inflammation (Fig. 1). This patient developed dyspnea on exertion, and spiral computed tomographic examination of the chest revealed a pulmonary embolism in the right lower lobe. Anticoagulation was initiated with enoxaparin followed by warfarin. Laboratory work-up for hypercoagulability mutations, including protein S, factor V Leiden, homocysteine, and anticardiolipin antibodies was negative. Fortunately, the patient’s symptoms resolved without long-term sequelae. Virchow’s triad (venous stasis, thrombophilia, and vascular endothelial injury) increases one’s risk of DVT. Thromboses often present in patients with advanced age, immobilization, surgery, trauma, malignancy, or hormone replacement therapy. Several clotting-factor mutations have also been implicated. This patient had two known risk factors: trauma and estrogen/progesterone medication. Foot and ankle surgeries are known precipitants of DVT, particularly in the postoperative period, but ankle sprains are obviously less likely to result in thrombus. The most serious complication of DVT is pulmonary embolism, with an estimated mortality of 30%. This seemingly minor scenario of an ankle sprain provides the following teaching points: (1) even minor limb trauma predisposes one to DVT, particularly if other risk factors are present, and (2) magnetic resonance imaging, which has been shown to be sensitive and accurate in identifying DVT, may be useful as a diagnostic aid.