aortocaval fistula ( acf ) mostly results from ruptured abdominal aortic aneurysm ( raaa ) , with a reported overall prevalence of 2% to 6% in patients with raaa .
these patients are always under emergency situations , which have a high mortality , but their clinical presentations may be quite variable . because this disease has variable clinical manifestations ,
the diagnosis is usually delayed , which increases the difficulties in treatment . both conventional open repair ( or ) and endovascular aneurysm repair ( evar ) have been used to treat this condition .
however , no patients with abdominal aortic dissecting aneurysm rupturing into inferior vena cava ( ivc ) have been reported , and there is also no standard therapy for this condition . because morphologic and hemodynamic characteristics of dissection are different from abdominal aortic aneurysm ( aaa ) , evar may be a more valid alternative over or in these patients .
we present a patient with acf from rupture of abdominal aortic dissecting aneurysm , which had a chronic course of disease .
evar was successfully performed for this patient , without endoleak and fistula at the follow - up .
prior to referral to our institution , the 70-year - old man had recurrent cough , anhelation , and chest distress .
about half a year before he came to our hospital , he had temporary abdominal pain , which disappeared spontaneously and suddenly .
he was treated as pneumonia at the local hospital . however , these symptoms aggravated gradually , so he was transferred to our hospital for further treatment . he had a history of tobacco abuse and chronic obstructive pulmonary disease , but no history of hypertension or heart disease .
physical examination revealed blood pressure of 126/63 mm hg , heart rate of 85  beats / min , and slight pitting edema of both lower extremities below the knee .
moist crackles could be documented on both lungs , and respiratory sounds were weakened at bilateral lower lobe of lung .
no abdominal tenderness or rebound tenderness was found , but a pulsating mass with continuous vascular bruit was recognized at the lower abdomen , without abdominal thrill .
laboratory results showed no hepatic or kidney dysfunction , hgb of 124  g / l , wbc of 12.29    10/l , bnp of 2625 pg / ml , troponin - t of 40.6 ng / l . chest computed tomography scans before admission showed severe pulmonary edema and inflammation ( figure 1a ) .
a later computed tomography angiography ( cta ) revealed an abdominal aortic dissecting aneurysm with an associated aortocaval fistula , no bleeding or hematoma in retroperitoneal space ( figure 1b ) .
echocardiography demonstrated that left ventricular ejection fraction was 45% , without abnormality of heart structure .
a , chest ct scans before admission revealed bilateral diffuse interstitial infiltrations and patchy shadow in both lungs , partial pulmonary atelectasis of both inferior lobes , together with a little pleural effusion .
b , preoperative reconstructed ct scan showed dissecting aneurysm and early opacification of inferior vena cava ( ivc ) , which indicated dissecting aneurysm had ruptured to form an aortocaval fistula ( arrow ) .
this elderly patient had a severe pulmonary disease and chronic heart failure ( chf ) , thus traditional or was extremely risky for him . however , because of the ruptured abdominal aortic dissecting aneurysm and the persistent venous hypertension , this patient had a critical need for operation .
minimally invasive endovascular intervention was performed immediately after the diagnosis was confirmed . under general anesthesia , bilateral common femoral arteries
this patient 's anatomy was suitable for evar according to cta and intraoperative angiography ( figures 2 and 3a ) . because the angle of neck was about 65 and this patient 's rarely complex condition , we implanted medtronic endurant suprarenal aortic devices . a bifurcated stent graft ( enbf2516c170ee ) ,
2 contralateral iliac limbs ( enlw1613c120ee , enlw1620c120ee ) , and an ipsilateral extension ( enlw1616c95ee ) were placed .
after these stent grafts were placed , proximal type i endoleak and fistula could be seen from angiography . to close the endoleak and fistula ,
finally , the endoleak and aortocaval fistula disappeared , which suggested evar was successful ( figure 3 ) .
a , computed tomographic angiography ( cta ) revealed false lumen of aorta ( ao ) directly rupturing into inferior vena cava ( ivc ) through a 6.9  mm fistula ( arrow a ) , and the maximal diameters of this dissecting aneurysm was 89  mm .
b , cta showed the aorta divides into true and false lumen through a 27.4  mm tear ( arrow b ) , which formed the abdominal aortic dissecting aneurysm .
c , cta showed the diameter of neck was 21.3  mm ( arrow c ) .
d , reconstructed ct scan revealed the length of neck is about 20  mm ( arrow d ) , and the angle of the neck is about 65. ct  =  computed tomography .
a , angiography showed fistula ( arrow a ) between false lumen of dissecting aneurysm and early opacification of inferior vena cava ( ivc ) .
b , after endografts were placed , angiography revealed proximal type i endoleak ( arrow b ) and early opacification of ivc ( arrow c ) .
c , after balloon dilatation was performed , angiography showed the endoleak and aortocaval fistula had disappeared .
he experienced a lengthy postoperative course including 20 days in intensive care unit due to pulmonary edema and pneumonia .
he was initially maintained on venous thrombus embolism ( vte ) prophylaxis with heparin during operation and then switched to low molecular weight heparin after operation .
when he discharged , edema of both lower limbs had resolved , and not only the pulmonary edema but also pneumonia had significantly relieved ( figure 4a ) . on the follow - up of 9th month , cta showed successful endovascular exclusion without endoleak or recurrent fistula .
a , chest ct scan before discharge showed pulmonary edema and inflammation had significantly relieved . from ( b ) and ( c ) , cta at the follow - up of 9th month after operation revealed no endoleak or fistula .
it is reported that the overall prevalence of acf is quite low , about 2% to 6% in patients with raaa .
the most common cause of acf is aneurysm erosion , especially in patients with raaa . on account of increased venous hypertension
however , acf usually results from raaa , so its most frequent symptoms should be abdominal pain and hemorrhagic shock . in our case , without bleeding in the retroperitoneal space , abdominal aortic dissecting aneurysm ruptured directly into ivc to form a fistula , which led to venous hypertension . therefore , the hemodynamics and clinical presentations of this patient were different from cases before .
in addition , fistula between false lumen of dissecting aneurysm and ivc is small , and the blood flow of false lumen in this case is much lower than that of true lumen .
therefore , the low blood flow of this fistula leads to chf and chronic pulmonary congestion , and the chronic pulmonary congestion may be the reason of repeated pneumonia for this patient .
the dramatic clinical presentation in this case is rare , which leads to delay of diagnosis .
another potential reason of delayed diagnosis may lie in the local doctor 's lack of associated knowledge . according to some reports , early diagnosis and intervention can double survival rates from 25% to 50% .
the diagnosis was not made until enhanced computed tomography was performed half a year after initial presentation , which was unfortunate for the patient .
the venous hypertension had leaded to a series of severe complications , such as pneumonia and heart failure .
in addition , patients with ruptured aortic aneurysm need emergency operation according to the guideline .
it is unknown whether endovascular intervention improves survival compared with traditional or for this disease . with the risk related to chf , massive intraoperative blood loss , and pulmonary infection , the surgical mortality of open repair ranges from 16% to 66% .
evar is valid in certain anatomical configurations and may be the optimal selection in terms of stent graft available . and
evar has potential benefits of less blood loss and no need for aortic cross - clamping during operation .
several cases of evar for raaa with acf have been described , with about 30% mortality , which had partially due to delays in diagnosis . accompanied with chf and chronic pulmonary congestion , the general condition of the elderly patient in our case was poor , he was not suitable for or . meanwhile , the anatomical configurations of our patient were suitable for evar .
furthermore , the morphologic and hemodynamic characteristics of dissecting aneurysm in our case are different from aaa or dissection before . therefore , evar was the best choice for this patient . in our case
, evar alone appears to have successfully isolated abdominal aortic dissecting aneurysm and closed the acf without the need of a stent - graft in the ivc . because of aortocaval fistulas and type ii endoleak
, persistent communication between the aneurysm and the ivc may exist . in some literatures , early placement of stent graft in the ivc
. however , no evidence demonstrated stent graft of ivc should be placed at the time of initial evar . because the chance of persistent aortocaval fistula after evar is rather small , endoleak and fistula
if persistent aortocaval fistula occurs , stent graft in ivc can be performed in the future . in our case ,
no fistula or endoleak were found at the follow - up of the 9th month .
in addition , because aneurysm sac debris may dislodge , prophylaxis of pulmonary embolism should be addressed . in our case ,
however , the chance of clinically significant pulmonary embolism is minute , and ivc filter placement may complicate the possible further ivc stent - graft placement .
diagnosis of this patient was delayed , but he fortunately had a successful operation and recovered finally . despite his poor general status and the high mortality associated with this condition , his complete recovery presents the potential for recovery with appropriate treatment .
further educational programs should be developed , which may give rise to earlier diagnosis and treatment with better outcomes .
 abstractaortocaval fistula ( acf ) after rupture of an abdominal aortic dissecting aneurysm is a rare emergency situation , which has a high mortality . 
 however , the diagnosis is usually delayed , which increases the difficulties of treatment . 
 we describe a case that successfully delayed use of endovascular aneurysm repair ( evar ) for acf resulting from rupture of abdominal aortic dissecting aneurysm.we describe a special case of a 70-year - old male with an abdominal aortic dissecting aneurysm rupturing into inferior vena cava ( ivc ) . on account of his atypical presentation , 
 the diagnosis had been delayed for half a year . due to severe metabolic sequelaes of the acf and preexisting conditions , 
 the traditional open repair was too risky . 
 minimally invasive evar was performed with a successful result . 
 there were no endoleak or fistula at the follow - up of 9th month.evar is the most suitable method in patients with acf from rupture of abdominal aortic dissecting aneurysm . 
 further educational programs should be developed , which may give rise to earlier diagnosis and treatment with better outcomes . 