Blood pressure shifts resulting from a concealed arteriovenous fistula associated with an iliac aneurysm: a case report

Abstract

BackgroundA 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.Case presentationA 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.ConclusionsDefinite 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.

An Ilio-iliac Arteriovenous Fistula Following Spontaneous Rupture of a Right Common Iliac Artery Aneurysm

“…4,5 The spontaneous rupture of a CIAA into an adjacent venous structure creating an IIAVF accounts for fewer than 1 % of all ruptures in CIAAs. 6 Trauma is usually the primary aetiology for presentation in intraabdominal arteriovenous fistula, with a variety of causes including gunshot wounds, stab wounds and seat belt trauma. Other causes such as malignancy, intervertebral disc surgery and other iatrogenic injuries have also been described.…”

“…[7][8][9][10] However, this triad of symptoms is present in only 20-50 % of reported cases, with their occurrence dependent on factors such as origin, size and location of the fistula, patient age and the presence of concomitant cardiac, liver and renal disease. [6][7][8] On serum blood tests, leucocytosis is usually present but unlike free aneurysmal rupture, the haemoglobin level remains stable. Initial renal function tests indicate decreased effective circulatory volume, which is nearly always reversible following repair.…”