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Year : 2006  |  Volume : 16  |  Issue : 4  |  Page : 453-456
Spontaneous aortocaval fistula due to abdominal aortic aneurysm rupture - a case report


Barnard Institute of Radiology, Madras Medical College, Chennai - 600003, India

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Keywords: aneurysm, transfemoral angiogram, atherosclerosis, fistulae, Endovascular stent

How to cite this article:
Ravi R, Peter S B, Swaminathan T S, Chandrasekar V. Spontaneous aortocaval fistula due to abdominal aortic aneurysm rupture - a case report. Indian J Radiol Imaging 2006;16:453-6

How to cite this URL:
Ravi R, Peter S B, Swaminathan T S, Chandrasekar V. Spontaneous aortocaval fistula due to abdominal aortic aneurysm rupture - a case report. Indian J Radiol Imaging [serial online] 2006 [cited 2019 Aug 20];16:453-6. Available from: http://www.ijri.org/text.asp?2006/16/4/453/32245

   Introduction Top


Spontaneous aortocaval fistula (ACF) is found in 1 % of all operations for an abdominal aortic aneurysm (AAA) and 4% of operations for ruptured aneurysms [1]. Early diagnosis and surgical treatment are necessary for a successful outcome. A case report of a 43-year old man, initially suspected to have unstable angina but subsequently diagnosed to have an aortocaval fistula is presented.


   Case report Top


A 43-year-old man was admitted with breathlessness on exertion grade III, pulsatile swelling of lower abdomen, chest pain of 6 months duration and swelling of leg & puffiness of face - 3 weeks. Vitals were normal except for mild tachycardia & elevated JVP.

On examination, pulsatile mass in umbilical region with bruit over it suggestive of an abdominal aortic aneurysm was found.

ECHO: RA, RV - hypertrophy, Mild PR, Mild TR .Normal LV Function with moderate PHT

X Ray Chest revealed mild cardiomegaly with prominent main pulmonary artery.

Plain x ray abdomen [Figure - 1] showed scalloping of anterior border of L3 vertebra.

Doppler ultrasound was done. There was abnormal and focal dilatation of infrarenal aorta with thick irregular walls and calcification.Colour Doppler mode showed extensive colour mix with aorta and IVC [Figure - 2] not separately visualized. On increasing the PRF there is turbulence within the aneurysmal segment of aorta and adjacent IVC with extensive aliasing at the level of communication between the aorta and IVC. Pulsatile arterialized flow was seen in the IVC with velocity of 110 cm / sec. [Figure - 3]


   Angiogram Top


Transfemoral angiogram revealed a saccular aneurysm of infrarenal aorta with a fistulous communication between the aorta and IVC at the level of L3 vertebra [Figure - 4]. Simultaneous opacification of IVC with proximal dilatation was observed.


   Computed tomography Top


CT showed a saccular infra-renal abdominal aortic aneurysm 8.5 cm in transverse diameter, with loss of demarcation between aorta and IVC[Figure - 5].Early detection of contrast material in the inferior vena cava during the arterial phase[Figure - 6], suggestive of an aortocaval fistula was confirmed.


   MRI/MRA Top


Contrast MRA was done. 20cc of gadolinium was used with a FLASH 3D sequence [Figure - 7]. This revealed similar findings to conventional angiogram.


   Discussion Top


Preoperative diagnosis of an aortocaval fistula is helpful in planning operative strategy, in preparing for the massive blood loss and for avoiding dislodgement of atheromatous debris that can embolise across the fistula causing pulmonary embolism.

Contrast MRA and CT angiogram are the imaging modalities of choice for diagnosis of an aortocaval fistula, being non-invasive [3]. Findings include early detection of the contrast medium in the dilated inferior vena cava, which is isodense/isointense with the adjacent aorta, an associated aortic aneurysm, loss of the normal anatomic space between the aorta and vena cava and rarely one can even visualize the abnormal communication between the aorta and vena cava, as seen in our case [6].

Pathophysiology

An AC fistula causes a sudden diversion of blood flow from high-resistance arterial circuit to low-resistance venous circuit. This produces a decrease in total peripheral resistance with an increase in venous resistance, venous pressure and volume. The heart rate, stroke volume, cardiac output and cardiac work are increased. The myocardium hypertrophies and then dilates, if untreated it leads to irreversible hyper dynamic cardiac failure. As blood is diverted through the fistula, arterial perfusion distal to the fistula is reduced. The raised renal venous pressure causes a decrease in the renal arterial perfusion pressure. The renin-angiotensin system is activated by the decreased distal perfusion and reduced renal arterial perfusion pressure. This leads to increase in the secretion of aldosterone, which, in turn, causes plasma expansion in an attempt to increase perfusion.

AC Fistula

L-R arteriovenous shunt

Reduction in mean systemic arterial pressure

Reduced perfusion pressure distal to fistula with increased venous return to heart which manifest as high output congestive cardiac failure

Abdominal aortic aneurysms (AAAs) represent a degenerative process of the abdominal aorta that is often attributed to atherosclerosis; however, the exact cause is not known. Degenerative aneurysms account for more than 90% of all infrarenal AAAs. Other causes include infection, cystic medial necrosis, arteritis, trauma, inherited connective-tissue disorders, and anastomotic disruption.

The disease generally affects elderly men. Smoking appears to be the risk factor most strongly associated with AAA.

Aneurysms are defined as a focal dilatation with at least a 50% increase over normal arterial diameter. Thus, an enlargement of at least 3 cm of the abdominal aorta fits the definition. Most cases of AAA begin below the renal arteries and end above the iliac arteries. They generally are spindle shaped; however, size, shape, and extent vary considerably. Of AAA cases 10-20% has focal outpouchings or blebs that are thought to contribute to the potential for rupture. The wall of the aneurysm becomes laminated with thrombus as the blebs enlarge. This can give the appearance of a relatively normal intraluminal diameter in spite of a large extraluminal size [2].
" Asymptomatic: Most patients present with an asymptomatic pulsatile abdominal mass.
" Rupture: The most typical manifestation of rupture is abdominal or back pain with a pulsatile abdominal mass.
" Peripheral emboli: Atheroemboli from small AAAs produce livedo reticularis of the feet or blue toe syndrome
" Acute aortic occlusion: Occasionally, small AAAs thrombose, producing acute claudication.
" Aortocaval fistulae: AAAs may rupture into the vena cava, producing large arteriovenous fistulae. In this case, symptoms include tachycardia, congestive heart failure (CHF), leg swelling, abdominal thrill, machinery-type abdominal bruit, renal failure, and peripheral ischemia [4].

Other causes include Trauma, laminectomy, Infection, Connective tissue disorder - Ehler Danlos & Marfans, Neoplasms. Most common site is distal posterolateral aorta and adjacent IVC.Other sites include aorta & iliac veins, aorta & renal vein.
" Aortoduodenal fistulae: Finally, an AAA may rupture into the fourth portion of the duodenum. These patients may present with a herald upper gastrointestinal bleed followed by an exsanguinating hemorrhage.

Management

Interventional Endovascular stent placement and Surgical. [5]

Criteria for stent: AAA < 4 cm, Aneurysmal neck <26 mm diameter, IR neck length of 1 cm.

With 'C' arm fluoroscope and with digital reconstruction to monitor the procedure through Seldinger technique both common femoral arteries catheterized for stent manipulation. Aortic segment of graft positioned immediately below the renal ostia without use of any proximal cuff .Grafts most commonly used are Vanguard bifurcated stent graft. Others include self expanding endograft, Dacron covered Palmez stent, Balloon expandable polytetrafluroethylene stents.After deployment an angiogram is done to assess adequacy of repair.

Conclusion

Spontaneous aortocaval fistula (ACF) is uncommon. Pre-operative detection is crucial for proper surgical management. Modern non invasive imaging provides accurate road map for the surgeon, similar to angiography. Demonstration of direct communication is possible with CE MRA.

 
   References Top

1.Baker WH, Sharzener LA, Ehrenhaft JL. Aortocaval fistula as a complication of abdominal aortic aneurysms. Surgery 1976;72:933-8.  Back to cited text no. 1    
2.Eisman B, Hughes RH. Repair of an abdominal aortic vena cava fistula caused by rupture of an arteriosclerotic aneurysm. Surgery 1956;39:498-04.  Back to cited text no. 2    
3.Lehman EP. Spontaneous arteriovenous fistula between the abdominal aorta and the inferior vena cava. Ann Surg 1938;108: 694-700.  Back to cited text no. 3    
4.Cortis BS, Jablokow VR, Shah AN, Cortis PF. Spontaneous rupture of an abdominal aortic aneurysm into the inferior vena cava: a case report and review of literature. Mt Sinai J Med (NY) 1972;39:566-72.  Back to cited text no. 4    
5.Umscheid T, Stelter WJ. Endovascular treatment of an aortic aneurysm ruptured into the inferior vena cava. J Endovasc Ther 2000;7:31-5.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]
6.Abram's Angiography - Vascular and interventional Radiology , IVth edition Vol 1 Page No 962   Back to cited text no. 6    

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Correspondence Address:
R Ravi
Barnard Institute of Radiology, Madras Medical College, Chennai - 600003
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-3026.32245

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    Figures

  [Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7]

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    Introduction
    Case report
    Angiogram
    Computed tomography
    MRI/MRA
    Discussion
    References
    Article Figures

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