Image: Clubbing and hypoxia

A 40-year-old male with no significant past medical history presented to the emergency department with a severe headache for 3 days. On physical examination, the patient appeared very uncomfortable and was hypoxic on room air to 86%. He was ambulatory with no apparent focal neurologic deficits, but his fingers were clubbed. Electrocardiogram showed normal sinus rhythm. Computed tomography (CT) angiogram of the chest incidentally revealed a portosystemic shunt in the left upper quadrant. CT brain and magnetic resonance imaging (MRI) brain with and without contrast were obtained (Figures 1 and 2). Brain abscesses can occur in individuals with hepatopulmonary syndrome, who are at higher risk due to intrapulmonary right-to-left shunting. This condition can arise from direct spread of nearby infections or, less commonly, from hematogenous spread, typically in the middle cerebral artery's territory from distant infections.1-3 Intrapulmonary right-to-left shunting can be caused by pulmonary arteriovenous malformations or hepatopulmonary syndrome, characterized by impaired oxygenation due to intrapulmonary vascular changes from liver disease or portal vein abnormalities. This condition is most common in patients with chronic liver disease. Capillaries in the lung dilate, causing a perfusion mismatch, theorized to result from bacterial translocation and release of inflammatory markers, leading to hypoxemia and dyspnea.4 Our case highlights an important risk factor for developing a brain abscess in a patient presenting with hypoxia and headache. Intrapulmonary shunts can lead to chronic hypoxia and paradoxical embolism, seeding infection into the cerebral vasculature. Diagnosis is made with MRI and brain biopsy, and treatment includes broad-spectrum antibiotics and neurosurgical drainage.