A case of lower extremity deep venous thrombosis with acute pulmonary embolism and resultant pulmonary infarction

A 74-year-old elderly male was brought to the emergency department with history of acute onset right-sided chest pain and mild fever. He had a history of on and off shortness of breath since last six months. No past medical history of diabetes or hypertension was noted.

Since the patient presented with acute onset of right-sided chest pain, initial evaluation was carried out with a chest X-ray. Chest X-ray showed a thin-walled cavitary lesion in the right mid zone (Fig 1). Bilateral pleural effusion was noted. Based on the chest x-ray findings, patient was evaluated in the line of infective pathology and contrast CT chest was done (that is why we do not have the pulmonary angiography images in this case). To our surprise, contrast CT showed hypodense filling defect in the right descending pulmonary artery (Fig 4, Fig 5) and segmental arteries (Fig 6) suggestive of pulmonary thromboembolism. Cavitating, wedge-shaped peripheral based consolidation suggestive of pulmonary infarction was also noted (Fig 2, Fig 3).  Doppler study of bilateral lower limbs revealed deep venous thrombosis of the left lower limb extending to the infra-renal inferior vena cava (Fig 7, 8, 9).

Background and clinical perspective: Pulmonary thrombo-embolism refers to the occlusion of the pulmonary arterial system by a thrombus or an embolus. It usually occurs following deep venous thrombosis of the lower limbs. A number of factors can lead to the increased risk of pulmonary thrombo-embolism such as prolonged immobilization, trauma, pregnancy, malignancy, hypercoagulable states (protein C and S deficiency) and oestrogen replacement therapy. Pulmonary infarction occurs only in a minority of patients with pulmonary embolism (10 to 15% of cases) [1].

Imaging Perspective: CT pulmonary angiography is the gold standard imaging modality for the evaluation of patients with pulmonary thromboembolism [2].  However, in cases of any suspected pulmonary pathologies, chest X-ray is usually the initial investigation carried out. Typical chest radiographic findings in cases of pulmonary thromboembolism with pulmonary infarction include enlarged central pulmonary artery with regional oligaemia and wedge-shaped juxtapleural opacification (Hampton's Hump). CT angiography shows non enhancing hypodense filling defect within the pulmonary arteries (suggestive of pulmonary thromboembolism) with peripheral wedge-shaped pulmonary consolidations (suggestive of pulmonary infarction). Cavitation may be seen in septic embolism and in cases of infection of a bland infarct (cavitatory pulmonary infarction) as in our case. In CT angiography, acute pulmonary embolism is noted as a hypodense filling defect surrounded by the contrast (Polo mint sign) and it makes an acute angle with the vessel wall [3]. Chronic pulmonary embolism, on the other hand, presents as asymmetric wall thickening of the vessel with the hypodensity making an obtuse angle with the vessel wall [4]. Nuclear study in the form of ventilation/perfusion scan can also be done in patients with suspected pulmonary embolism. Ventilation-perfusion study shows areas of ventilation-perfusion mismatches [5]. A study showing two or more unmatched segmental perfusion defects is considered to be a high probability study. Doppler study of lower limbs should be carried out in all patients with pulmonary embolism so as to rule out the deep venous thrombosis of the lower extremities as the potential cause of pulmonary thromboembolism.

Treatment and outcome: In all patients with pulmonary thromboembolism, with or without pulmonary infarction, the initial treatment is the cardiopulmonary support. In those patients with no risk of active bleeding, anticoagulation should be started. In cases of patients with massive emboli, thrombolysis can be undertaken. Pulmonary artery embolectomy with placement of vena cava filters can help in preventing further episodes of pulmonary thromboembolism.

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