Blood pressure shifts resulting from a concealed arteriovenous fistula associated with an iliac aneurysm: a case report
© The Author(s) 2016
Received: 2 June 2016
Accepted: 11 October 2016
Published: 21 October 2016
A solitary iliac aneurysm (SIA) is more uncommon than an abdominal aortic aneurysm. The aneurysm is located in the deep pelvis and is diagnosed when it reaches a large size with symptoms of compression around adjacent structures and organs or when it ruptures. A definite diagnosis of an arteriovenous fistula (AVF) associated with a SIA is difficult preoperatively because there might not be enough symptoms and time for diagnosis. Here, we present a patient with asymptomatic rupture of SIA into the common iliac vein with characteristic blood pressure shifts.
A 41-year-old man with a huge SIA underwent aortobifemoral graft replacement. Preoperatively, his blood pressure showed characteristic shifts for one or two heartbeats out of five beats, indicating that an AVF was present and that the shunt was about to having a high flow. During surgery, an AVF associated with the SIA was found to be concealed owing to compression from the huge iliac artery aneurysm, and the shunt showed a high flow, resulting in shock during the surgery. No complications were noted after aortobifemoral graft replacement. Postoperatively, we noted an enhanced paravertebral vein on computed tomography (CT), which indicated the presence of an AVF.
Definite diagnosis of an AVF offers advantages in surgical and anesthetic management. We emphasize that a large SIA can push the iliac vein and occlude an AVF laceration, concealing the enhancement of the veins in the arterial phase on CT. Blood pressure shifts might predict the existence of a concealed AVF that has a large shunt. Even if the vena cava and the iliac veins are not enhanced on CT, anesthesiologists should carefully determine whether their distal branches are enhanced.
KeywordsAbdominal aortic aneurysm Arteriovenous fistula Hemodynamics Iliac artery
A solitary iliac aneurysm (SIA), an aneurysm that locates only in the iliac artery, occurs in 0.6 % of the case of an abdominal aortic aneurysm (AAA) , and many of the patients are free of symptoms. The aneurysm is located in the deep pelvis and is diagnosed when it reaches a large size with symptoms of compression around adjacent structures and organs or when it ruptures. An ilio-iliac arteriovenous fistula (AVF) occurs in less than 1 % of all cases of a common iliac artery aneurysm . Because of its rarity and its various symptoms, the diagnosis and treatment of an AVF associated with a SIA are challenging to vascular surgeons and anesthesiologists. Here, we present a patient with asymptomatic rupture of a SIA into the common iliac vein with characteristic blood pressure shifts.
We presented a case of acute aneurysmal rapture into the iliac vein. Sometimes, a definite diagnosis of an AVF associated with a SIA is difficult preoperatively because there might not be enough symptoms and time for diagnosis . An AVF associated with an AAA has the following triad of symptoms: congestive heart failure, continuous abdominal bruit, and a pulsating abdominal mass ; however, these symptoms are noted in only 20–50 % of reported cases . An AVF associated with a SIA might show lower limb edema as an additional feature; however, many cases do not have hemodynamic symptoms [4–6]. Definite diagnosis of an AVF offers advantages for surgical and anesthetic management.
Arterial pressure shifts rarely occur in a clinical situation. In the present case, these shifts indicated that an AVF was present and that the shunt was about to having a high flow. These hemodynamic changes could be explained by pooling of the transient increased shunt flow to a high-capacitance venous circuit and a decreased in preload, which can produce low arterial pressure at the next heartbeat. Simultaneously, an increase in venous return raised the blood pressure following a downward shift in the blood pressure. We hypothesized that the mechanical compression of a huge aneurysm should occlude the AVF and the fistula would appear by changing of lower limb posture, high blood pressure, or pulse of the aneurysm itself. The shift disappeared during the operative preparation, indicating that shunt dilation due to anesthetic agents and muscle relaxants decreased peripheral resistance, including aneurysmal compression at the vein.
We report a patient with asymptomatic rupture of a SIA into the common iliac vein with characteristic blood pressure shifts. It was believed that the AVF did not cause a shock preoperatively because the laceration was small, the aneurysm ruptured into a relatively minor vein, and the huge aneurysm decreased shunt flow owing to compression of the common iliac vein. The blood pressure shifts indicated that the shunt of the AVF was about to open completely. Even if the vena cava and the iliac veins are not enhanced on CT, anesthesiologists should carefully determine whether the paravertebral vein and the ascending lumbar vein are enhanced. Detection of minor enhancement of these veins will help in the early diagnosis of a concealed AVF, thus preventing morbidity and mortality.
Abdominal aortic aneurysm
Central venous pressure
Solitary iliac aneurysm
SD participated in the study design, data collection, data analysis, and manuscript preparation. YM and HI were assigned in data collection. All authors read and approved the final manuscript.
The authors declare that they have no competing interests.
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