a patent foramen ovale ( pfo ) can act as a pathway for a thrombus from the peripheral veins , bypassing the lungs and entering the systemic circulation .
systemic , noncerebral , paradoxical embolisms occur less frequently , accounting for 5%10% of all paradoxical embolisms .
renal infarction secondary to paradoxical embolism has rarely been described , and paradoxical embolism involving kidneys has been reported to commonly involve multiple organs , such as the lung , kidneys , and brain . here , we report a case of a paradoxical embolism caused by pfo involving only kidneys .
a 48-year - old korean man was referred to our hospital with sudden right flank pain that had begun 10 days earlier .
he had been diagnosed with idiopathic thrombocytopenic purpura ( itp ) 10 years earlier , but his platelet counts had been stable ( > 50,000/l ) with no significant bleeding , over the past 10 years . he had undergone a hemorrhoidectomy two months earlier . he was a 30-pack - year smoker and an occasional drinker , with no noteworthy family medical history . on admission ,
the patient 's blood pressure was 107/68  mm hg and his pulse rate was 78 beats / minute .
his respiratory rate and body temperature were 18 breaths / minute and 36.3  c , respectively .
his neurologic findings were normal , and neither edema nor bruising was found on the lower extremities .
blood test results showed a low platelet count ( white blood count 6,800/l , hemoglobin 12.4  g / dl , platelet 63,000/l ) , and his serum creatinine was 0.83  mg / dl and blood urea nitrogen 13.0  mg / dl .
urine microscopy revealed mild hematuria ( red blood cell count 35/hpf ) and pyuria ( white blood cell count 1120/hpf ) .
his levels of antithrombin iii activity , plasminogen activity , protein c activity , coagulation factor viii activity , homocysteine , lupus anticoagulant , and anticardiolipin antibody were within the normal ranges , suggesting no abnormality of the coagulation system .
a contrast - enhanced abdominal computed tomography ( ct ) scan was performed in the previous hospital , showing no stones , but a wedge - shaped perfusion defect was detected in the right kidney , suggestive of renal infarction ( fig .
1 ) . contrast - enhanced abdominal magnetic resonance ( mr ) angiography was performed to exclude the possibility of a renal artery thrombus or dissection .
because the patient 's renal arteries were intact despite acute renal infarction , the filling defect was suspected to be caused by embolization , and the cortical scars on the left kidney suggested the possibility of previous recurrent renal infraction .
a duplex lower extremity vein scan showed no obvious thrombosis in the deep venous system , which is a frequent potential source of an embolism .
electrocardiography showed a normal sinus rhythm , and transthoracic echocardiography revealed no thrombus , but normal left ventricular function .
however , a contrast study and bubble test during transesophageal echocardiography revealed a small pfo ( fig .
3a ) . from these findings , a paradoxical embolism through a small pfo was confirmed as the cause of the patients multifocal renal infarction .
the patient had been given intravenous heparin for his renal infarction in the previous hospital . during the heparin treatment ,
he developed hemorrhoidal bleeding , and underwent hemorrhoid ligation and discontinued anticoagulation . therefore , pfo closure was planned to prevent further embolic events and bleeding complications , which can recur under anticoagulation therapy .
the diagnosis of acute renal infarction is often missed or delayed because the disease is both rare and has a nonspecific clinical presentation . in a patient with an increased risk of thromboembolism
diagnostic tests should be considered for patients who are at risk of systemic embolization and present with symptoms suggestive of renal infarct .
a contrast - enhanced ct scan should be performed to look for renal infarction , for which the classic finding is a wedge - shaped perfusion defect .
two major causes of renal infarction are thromboemboli , which usually originate from a thrombus in the heart or aorta and in situ thrombosis of a renal artery or renal artery dissection , which is less common .
the major sources of a clot embolism include the left atrium during atrial fibrillation , a left ventricular thrombus in patients with myocardial infarction , and thromboemboli originating from complex plaques in the aorta .
other potential embolic sources include valvular vegetations in patients with infective endocarditis and , rarely , paradoxical embolism through a pfo .
the foramen ovale , which allows blood to flow across the atrial septum in the fetal stage , normally closes shortly after birth .
however , in approximately 25% of adults , closure of the foramen ovale is incomplete .
when a right - to - left shunt exists across the pfo , thrombi , and vasoactive substances formed in the right - side venous circulation can bypass the lung filter and enter the left arterial system , causing a paradoxical embolism .
although the vast majority of people with pfo are asymptomatic , the presence of pfo has been implicated in stroke , migraine headache , decompression sickness , high - altitude pulmonary edema , and platypnea - orthodeoxia syndrome .
although ischemic events can occur in most organs , including the brain , eyes , kidneys , spleen , and intestines , and in the upper and lower extremities , stroke is the most usual common manifestation of paradoxical embolism .
the prevalence of pfo is estimated to be 45% among patients with cryptogenic stroke or transient ischemic attacks . in a recent study the most common reason for the primary referral of patients with pfo - related conditions for pfo closure ( n=416 ) was cryptogenic stroke ( n=219 ) .
noncerebral paradoxical embolism was rare ( n=12 ) and 75% of noncerebral embolisms were myocardial infarctions ( n=8 ) . whereas myocardial infarction is a rare complication of paradoxical embolism through pfo , there are even fewer reports of renal infraction in patients with pfo .
most patients reported with paradoxical renal infarction present with multiorgan involvement and have multiple acute ischemic symptoms , such as dyspnea and abdominal pain .
this case is unique in that the patient had acute flank pain and the embolism was confirmed only in the kidneys , with no other organ involvement .
secondary prophylaxis for a paradoxical embolism can involve pharmacotherapy or the closure of the right - to - left shunt , which can be performed surgically or with a transcatheter procedure .
the efficacy of the devices used to prevent recurrent systemic arterial embolisms , and in particular cerebrovascular embolisms , is unknown but is currently under investigation in large - scale clinical trials .
closure of the pfo after the first embolism is recommended for patients at high risk of recurrent embolic events .
the risk factors associated with embolic recurrence include atrial septal aneurysm , high shunting volume , and shunting at rest .
other risk factors include large pfo ( more than 3.4  mm ) , higher mobility of the pfo valve , a well developed eustachian valve , a valsalva maneuver immediately prior to event , and a history of recurrent embolic events .
pfo can be closed percutaneously with a low rate of significant residual shunting and very few complications .
after closure of the pfo , no patient experienced a recurrent paradoxical embolic event during the medium - term ( up to four years ) follow - up period . in this case , the patient also had long - standing itp when his renal infarction occurred .
his platelet count had not changed for 10 years , without treatment . given that his coagulation profile was normal and there was no thrombosis in the renal artery ,
because he had no obvious source of emboli , we used contrast echocardiography and a bubble test during the valsalva maneuver to examine the possibility of a paradoxical embolism and confirmed the diagnosis of paradoxical renal infarction caused by pfo .
echocardiography shows that he has a shunting not only at valsalva but also at rest .
and the patient was suspected of having had recurrent renal infractions in the past based on mr angiography findings .
so , secondary prophylaxis was required to prevent additional embolisms . because he suffered hemorrhoidal bleeding during heparin treatment and his platelet count was low ,
the insertion of a transcatheter pfo closure device was planned , considering the potential problems associated with maintaining oral anticoagulation therapy . in conclusion , the role of pfo as a source of ischemic events in various organs is becoming increasingly evident .
this case suggests that renal infarction can be caused by a paradoxical embolus from a pfo .
paradoxical embolism is a rare cause of renal infarction , but immediate recognition of a paradoxical embolus is very important so that anticoagulation or device closure can prevent further embolic infarctions in other organs , as well as in the kidneys . if renal infarction occurs repeatedly , with no evident cause of the thromboembolism or during anticoagulation therapy , a paradoxical embolism through a pfo should be considered .
 a 48-year - old man presented with acute right flank pain . a computed tomography scan revealed right renal infarction . 
 because he had no thrombosis in the renal vessels and no clear embolic source , a further examination was performed to find the cause of the renal infarction . 
 on transesophageal echocardiography , a right - to - left shunt during the valsalva maneuver established a diagnosis of patent foramen ovale . 
 this is a case of paradoxical embolism through a pfo leading to renal infarction . 
Introduction
Case report
Discussion
Conflict of interest