The AV fistula had the origine of right internal iliac artery and drains off blood to right internal iliac vein.
Arteriovenous malformations (AVMs) of the female pelvis are uncommon. These may either be congenital or acquired. Congenital pelvic AVMs are characterised by a large number of arterial feeding branches. The arterial feeders are considered undifferentiated vascular structures following arrested embryonic development at various stages . Acquired pelvic AVMs on the other hand, develop following spontaneous rupture of an atherosclerotic aneurysm into the adjacent veins or following penetrating trauma (less than 20%), e.g. gunshot wound or stabbings, or after lumbar disc surgery . Therefore, acquired AVMs are most commonly arteriovenous fistulas (AVF). The AVFs are most commonly aorto-caval fistula, followed by ilio-iliac  and aorto-iliac. However, the etiology, clinical features, pathophysiology, principles of management and postoperative care for these fistulas are similar. Approximately 3 to 4% of all patients undergoing surgery for ruptured aorto-iliac aneurysm are found to have AVF . These carry a better prognosis than intraperitoneal, retroperitoneal or enteric rupture of aorto-iliac aneurysms . The disorder has a marked male preponderance . Other rarer causes of acquired AVFs include Marfan’s syndrome, Ehler-Danlos syndrome, syphilis, Takayasu’s arteritis, invasion by malignant tumour  and in some the cause is never ascertained.
Pelvic AVMs may manifest with symptoms of pain, haemorrhage, haematuria, dyspareunia, or congestive heart failure, or symptoms secondary to mass effect on adjacent pelvic structures. Acquired AVF, secondary to surgery or trauma, tend to occur in younger patients as trauma or surgery tends to affect younger patients. In contrast, spontaneous perforation of atherosclerotic aneurysm into adjacent veins tends to occur in the older population. Two large series report mean ages of 67.3  and 69.7 years. The time of onset of symptoms is usually earlier, from hours to weeks . The initial diagnosis is often that of an abdominal aortic aneurysm, AVF is often not suspected and often the diagnosis is only made at surgery .
Iliac artery aneurysms and ilio-iliac fistulas are usually associated with abdominal aortic aneurysm, as demonstrated in this case, though they may occur as isolated entities. Rupture of atherosclerotic aneurysms into the iliac vein may have three different clinical manifestations: sudden onset of high output cardiac failure; pulsatile lower abdominal mass associated with bruit and thrill; or unilateral intermittent claudication or venous congestion. Our patient presented with the first two clinical manifestations and the tricuspid regurgitation was most likely secondary to grossly dilated ventricle from high output cardiac failure.
Ultrasound, CT or even MRI is almost always ordered for assessment of the abdominal/iliac aneurysms. Colour Doppler ultrasound has demonstrated the AV fistulas as areas of high velocity turbulent flow with aliasing of colour signal and also shows any associated thrombus at the aneurysm or fistula. Detection of ilio-iliac fistulas may however be difficult, as demonstrated by this case, as these tortuous and aneurysmal vessels lie deep within in the pelvis and obscured by overlying bowel gas. CT angiography is excellent in demonstrating the aneurysm and fistulous communications , especially with the advent of multi-detector CT and 3D software. Early contrast opacification of the iliac veins and inferior vena cava, and site of the fistula are clearly visualised.
Conventional angiography still remains the ‘gold standard’ for assessment of AVMs as well as assisting in assessing options for endovascular management. Endovascular treatment has gained considerable favour in the management of arteriovenous fistula especially for those with significant high-risk comorbid factors. Options available include percutaneous endovascular treatment with covered self-expanding stent graft to cover the mouth of the fistula. However, this is not always feasible due to the tortuous iliac vessels. Transcatheter embolisation with coils or detachable balloons  is generally not recommended due to the large size of the fistula, high flow and short neck.
Surgical options for AVF consist of endo-aneurysmal repair of the fistula and prosthetic graft replacement of the aortoiliac aneurysm but these are associated with high morbidity and mortality (approaching 60%) due to the emergent nature of the procedure . Thus early diagnosis and appropriate management is of paramount importance. Unlike acquired AVFs, surgical treatment of congenital AVMs is difficult due to the extensive nature and the large number of dysplastic feeder vessels with the potential for exsanguinating haemorrhage and damage to surrounding structures . Accordingly, transcatheter embolisation has become the treatment of choice . Preoperative embolisation of AVMs has also been used as an adjunct to decrease intraoperative blood loss. Small asymptomatic AVMs that do not increase in size may be safely observed.
AVFs between major abdominal vessels are uncommon complication of aortoiliac aneurysm. Ilio-iliac fistula in a female patient is even rarer and associated with high morbidity and mortality especially if the diagnosis is not suspected. In this patient, in the absence of history of trauma or surgery and the presence of extensive aneurysmal disease involving the aorta and iliac arteries, it is reasonable to believe that the AV fistula was secondary to perforation of the aneurysmal right iliac artery into the right iliac vein. In addition to the rapid onset, the presence of a single communication and older age group lend more support to this diagnosis.
There has only been a single reported case in the literature with an ilio-ilial fistula secondary to atherosclerotic disease . In addition the CT angiographic appearances of ilio-ilial AVF have not been described.
Spontaneous major intra-abdominal arteriovenous fistulas: a report of several cases, Astarita D, Filippone DR, Cohn JD. Angiology1985, Sep;36(9):656-61.
Most major intra-abdominal fistulas result from trauma or surgery. Spontaneous fistulas are rare with less than 100 reported cases since 1831. From a review of hospital records, five such spontaneous fistulas were identified among 215 cases of abdominal aortic aneurysm between 1975 and 1983. These cases are presented and supplemented by 73 similar cases collected from a literature review for discussion of the salient features of clinical presentation and management of spontaneous major fistulas. Major intra-abdominal arteriovenous fistulas usually present with a machinery bruit over a pulsatile mass, but may present more subtly with pain and otherwise unexplained hematuria. Because these fistulas lead to refractory heart failure, surgery should be expeditious. Closure should be performed from within the aneurysm with arterial and pulmonary artery pressure monitoring. Care must be taken to prevent pulmonary embolization.