Renal artery aneurysms (RAA) are the second most common visceral aneurysm (15-22%), the most common being splenic artery aneurysm (60%).
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Epidemiology
Renal artery aneurysms occur in ~0.1% of the population 6,8. They are more common in females 6 . The median age at diagnosis is 50 years 8.
Clinical presentation
Most cases are asymptomatic. Symptoms usually arise from rupture of an aneurysm, embolization of the 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.
In pregnancy, the acute, severe unilateral flank pain induced by maternal renal artery aneurysm rupture is usually attributed to a number of other, more common causes. This explains in part the high maternal and fetal mortality rate, which is why it should always be on the list of differential diagnoses, especially if followed by dropping blood pressure 10.
Pathology
Approximately 20% of cases are bilateral. Most 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
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 amenable 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 renal artery aneurysm rupture is associated with a high mortality for both mother and fetus.
Follow-up for renal artery aneurysm 5:
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1.0-1.5 cm: can be safely followed 6
follow-up in 1-2 years, as long as the patient is not premenopausal (see above)
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>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 renal artery aneurysm: embolization
main renal artery aneurysm: ligation and bypass surgery, nephrectomy or stent placement
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