From kidney to kidney : an unusual case of paradoxical embolism through a patent foramen ovale in the course of a massive pulmonary embolism

Introduction: The patent foramen ovale (PFO) has been linked to paradoxycal embolism (PaE) with cryptogenic stroke, transient ischemic attack, systemic embolization. In this context pulmonary embolism (PE) has been previously described as a favoring condition due to the resulting pulmonary hypertension (PH). Case presentation: A 59 years old healthy male presented to the Emergency Room with worsening dyspnea (NYHA class III) since 2 months. ECG showed sinus tachycardia, pulmonary P waves Rv strain (Fig.1). Room air oxygen saturation was 88%. Blood sample showed mild renal impairment, increased level of troponin and BNP. A transthoracic echocardiogram showed dilatation of the right ventricle with PH (PAPs 70mmHg). After intravenous agitated saline contrast injection a moderate interatrial right-to-left shunt was demonstrated (Fig. 2). A contrast-enhanced computed tomography (CT) highlighted bilateral massive PE with a huge override thrombus at the pulmonary artery bifurcation (Fig. 3a,b), bilateral renal ischemic lesions (Fig.3c) and a right kidney mass suspected for malignancy (Fig.3d). Lower limbs ultrasonography (CUS) showed no deep venous thrombosis. Patient was successfully treated with i.v. heparin during the first 72 hours followed by long term direct oral anticoagulants (DOACs, Apixaban 5mg bd). At 6 months he is asymptomatic (NYHA class I) and a CT scan showed an almost complete resolution of previous PE. Discussion and conclusions: Coexistence of PE and systemic embolism should always suggests the presence of paradoxical embolism. Under normal physiological conditions PFO allows a small amount of L-R shunt without no significant hemodynamic changes. However, in the setting of increased right atrial pressure, significant right to left shunt can occur and lead to paradoxical embolism. In this case the only detectable cause of embolism is a renal mass, suspected for malignancy, leading to a peculiar “thrombus route” through the pulmonary artery, the PFO and finally again to the kidneys. In conclusion our case suggests that an abrupt increase in PAPs due to paraneoplastic PE created a paradoxical embolization to the kidneys through an otherwise silent PFO.