CTICasesSystemic-to-Pulmonary Arterial Fistulae from Prior Tuberculosis Mimicking Chronic PE
Imaging findings
Chest radiograph demonstrates unilateral right-sided rib notching involving the third through fifth ribs, with abnormal vascular density in the right upper lobe. CT angiography shows a network of enlarged intercostal arterial collaterals fistulating into the pulmonary arterial branches of the right upper lobe, producing filling defects on CT that were initially misdiagnosed as pulmonary emboli and subsequently as chronic PE with V/Q mismatch. Pulmonary arteriography from 2013 shows absent or reversed flow in the right upper lobe pulmonary arteries with direct visualization of the fistulous connections from intercostal arteries. The underlying cause is right upper lobe fibrocavitary post-tuberculous scarring with calcified granulomas.
Key takeaways
Systemic-to-pulmonary arterial (smoke) fistulae arising from prior TB can be chronically misdiagnosed as pulmonary embolism and chronic thromboembolic pulmonary hypertension. The diagnostic clue on plain radiography is unilateral rib notching from enlarged intercostal arteries. On CT, the filling defects from reversed flow in pulmonary artery branches exactly mimic clot. V/Q mismatch persists because pulmonary blood flow is truly absent in the affected segments (fistulae supply the parenchyma directly). Pulmonary arteriography is definitive.
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