Aorto-left renal vein fistula

Last revised by Bahman Rasuli on 2 Oct 2020

Aorto-left renal vein fistula is an extremely rare complication of abdominal aortic aneurysm rupture. The initial clinical presentation is often non-specific, however, characteristic imaging findings, if recognized early, can lead to prompt diagnosis and assist in surgical planning. 

Spontaneous aorto-left renal vein fistula most commonly involved a variant retroaortic left renal vein and less commonly seen in trauma or post-surgical complications. 

Clinical presentation is often non-specific, which includes abdominal, left flank and groin pain.  It can mimic gastrointestinal and urologic conditions. Specific clinical findings include palpable pulsatile aorta or bruits on auscultation. Hematuria is often a presenting feature and most often the patient has an abnormal renal function 1.

The variant retroaortic left renal vein traverses between the aorta and the vertebral column. It is proposed that the pulsation of an abdominal aortic aneurysm over time result in pressure necrosis and the development of a spontaneous aorto-left renal vein fistula. This is typically associated with a contained retroperitoneal rupture of the abdominal aortic aneurysm. Fistula formation leads to a drastic elevated left renal venous pressure, characterized by distended renal veins and an enlarged left kidney. When this venous pressure gradient overcomes the arterial pressure, the left kidney becomes non-perfused. Numerous venous collateral vessels, most often the paravertebral but also gonadal venous channels, become distended. Prompt diagnosis is critical to prevent venous infarction of the left kidney and ensuing mortality.

Post-traumatic aorto-left renal vein fistulas may result from complications of penetrating abdominal trauma (e.g. gunshot and stabbing injuries) 2-4.

The imaging findings on CT complements on the pathophysiologic process described above. Careful multiplanar evaluation of the left posterolateral aspect of the aorta is paramount to identify the location of the fistula and site of the retroperitoneal abdominal aortic aneurysm rupture.  

Besides the abdominal aortic aneurysm, a non-perfused and enlarged left kidney is often what catches the eye of the radiologist. Hemorrhage/hematoma in the renal pelvis is a common associated finding, although the exact mechanism is not elucidated. The constellation of all these features should prompt the radiologist of the diagnosis. The use of 3D reformat is a delight for the vascular surgeon.

Duplex sonography, MRI, and catheter angiography may also demonstrate the abnormal communication between the abdominal aorta and left renal vein as well as the associated findings 5

Treatment options include surgical and endovascular repair. Mortality following repair of the aorto-left renal vein fistulas is less in cases caused by trauma compared to those formed as complications of abdominal aortic aneurysms 3.

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Cases and figures

  • Case 1: post-traumatic
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