Inferior phrenic artery–to–pulmonary artery fistula after surgery for catamenial pneumothorax: a case report

Background: Systemic artery–to–pulmonary artery fistula (SAPAF) is a rare vascular anomaly, and involvement of the inferior phrenic artery is particularly uncommon. Acquired SAPAF may occur as a late postoperative complication; however, diagnosis is often challenging because of subtle imaging findings and complex hemodynamics. Four-dimensional CT angiography (4D-CTA) enables time-resolved assessment of blood flow and may facilitate accurate diagnosis and treatment planning. Case presentation: A 56-year-old woman was referred to the respiratory department after screening chest CT, performed as part of an evaluation for suspected malignancy due to elevated tumor markers detected during a routine health checkup, revealed a suspected right pulmonary arteriovenous fistula. During further evaluation, it was confirmed that she had undergone thoracoscopic wedge resection of the right middle lobe and partial diaphragmatic resection for catamenial pneumothorax 10 years earlier. She was asymptomatic at presentation. Dynamic 4D-CTA demonstrated absence of opacification of the right A9 segmental pulmonary artery during the pulmonary arterial and venous phases, with retrograde filling of a tortuous vessel arising from the right inferior phrenic artery, suggesting an inferior phrenic artery–to–pulmonary artery fistula. Digital subtraction angiography confirmed the diagnosis, and coil embolization was successfully performed. Post-embolization angiography showed complete occlusion of the feeder artery and disappearance of the shunt. Conclusions: This case illustrates a previously unreported late postoperative complication after surgery for catamenial pneumothorax and highlights the clinical utility of 4D-CTA as a noninvasive modality for hemodynamic assessment and decision-making in the management of SAPAF.