Renal artery aneurysm

Renal artery aneurysms (RAA) are considered the second most common visceral aneurysm (15-22%), most common being splenic artery aneurysm (60%). 

Epidemiology

RAAs occur in ~0.1% of the population ^6,8. They are more common in females ⁶ with a median age of diagnosis of 50 years ⁸.

Clinical presentation

Most cases are asymptomatic. Symptoms usually arise from rupture of an aneurysm, embolization of peripheral vascular bed or arterial thrombosis ¹. Hypertension is associated with ~75% of cases of these aneurysms. Hematuria has also been reported in many cases.

Pathology

Approximately 20% of cases are bilateral. Mostly, the aneurysms are saccular and tend to occur at the bifurcation of the main renal artery or first-order branch ⁸. 

Etiology

• fibromuscular dysplasia (FMD): 35%
• degenerative aneurysm: 25%
• vasculitides, e.g. Behcet disease
• phakomatoses, e.g. tuberous sclerosis, neurofibromatosis
• intrinsic collagen deficiency, e.g. Marfan syndrome, Ehlers-Danlos syndrome
• trauma ^1,2

Radiographic features

CT

• non-contrast: soft tissue mass lesion in the region or course of renal artery
• post-contrast: contrast-filled outpouching in the course of the renal artery

Angiography (DSA)

Aneurysms can be well detected and characterized by angiography, in terms of size, neck diameter and type.

Classification

One classification method proposed by Rundback et al is at follows ⁹

• type 1: saccular aneurysms arising from the main renal artery or the large segmental branch: usually amendable to an endovascular approach
• type 2: fusiform aneurysms: may require an open surgical approach
• type 3: intra-lobar aneurysms arising from small segmental arteries or accessory arteries

Treatment and prognosis

Management depends on various factors like age, sex, severity of hypertension, anticipated pregnancy, and aneurysm morphology. In any young female with anticipated pregnancy, embolization or endovascular intervention is suggested. Pregnancy-associated RAA rupture is associated with 80% mortality.

Follow-up for renal artery aneurysm ⁵:

• 1.0-1.5 cm: can be safely followed ⁶
  • follow-up in 1-2 years, as long as the patient is not premenopausal
• >1.5 cm
  • consider surgical or endovascular repair
  • surgical treatment is recommended for aneurysms >2 cm in size

Modality of management depends on location:

• branch RAA: embolization
• main renal artery RAA: ligation and bypass surgery, nephrectomy or stent placement