Renal Arteriovenous Malformations And Arteriovenous Fistulas

Classification

According to their pathogenesis, renal lesions with an abnormal communication between the renal artery and the renal vein can be classified as congenital AVMs (developmental) and acquired AVFs (traumatic, spontaneous, or neoplastic).

AVFs account for 70% to 80% of abnormal renal arteriovenous communications. Traumatic AVFs may be extrarenal or intrarenal. Extrarenal AVFs involve the main renal artery and renal vein and are often caused by nephrectomy or by penetrating injury. Intrarenal AVFs can involve the segmental, interlobar, and arcuate renal arteries and are most commonly caused by renal biopsy or by trauma, either blunt or penetrating. Spontaneous fistulas may be associated with renal artery disease, such as renal artery aneurysm and arterial fibrodysplasia.

AVMs are congenital, are characterized by an arteriovenous communication at the arteriole and venule level, and are usually supplied by multiple feeding arteries ( Figures 1 and 2 ). These malformations are either cirsoid, with multiple arteriovenous communications, or cavernous, with well-defined arterial and venous channels. In contrast, the acquired AVF usually has a single feeding artery supplying a direct communication between an artery and a vein ( Figure 3 ).

Incidence

The true incidence of abnormal renal AV communications is unknown. In a review of 9500 renal arteriograms over a period of 13 years in 1978, Cho and Stanley found 21 patients with nonneoplastic abnormal arteriovenous communications. The lesions included four patients with congenital AVMs, 11 patients with traumatic AVFs, and six patients with spontaneous AVFs, including renal arterial aneurysmal rupture (three patients), arterial fibrodysplasia (two patients) and suspected arteritis (one patient). The types of trauma were blunt abdominal trauma, percutaneous renal biopsy, and open wedge biopsy.

Clinical Features

Clinical manifestations of renal AVMs and acquired AVFs depend on their size, location, and cause. Although nontraumatic and nonneoplastic AV communications are usually silent clinically, they have been alleged to cause hematuria, hypertension, spontaneous rupture, and heart failure. Symptomatic congenital AVMs usually manifest with hematuria varying in severity and uncommonly present with hypertension. Rarely, massive hematuria occurs with hypotension requiring blood transfusion. Hematuria is the most common presentation in traumatic fistulas. A large AVF can increase the size of the renal arteries and lead to high-output heart failure and renal insufficiency. Most patients with spontaneous AVFs associated with renal artery disease are hypertensive and rarely have hematuria. Decreased renal perfusion distal to the fistula is speculated to be a cause of renovascular hypertension, but a definite cause-and-effect relationship has not been well established.