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Open Surgical Treatment of Pararenal and Suprarenal Abdominal Aortic Aneurysms
Pararenal abdominal aortic aneurysms (AAAs) are an uncommon but important category of aortic disease. Pararenal AAAs are classified as being juxtarenal ( Figure 1 A) or suprarenal ( Figure 1 B) in location. Juxtarenal AAAs extend superiorly to just below the renal arteries such that no normal aorta exists between the aneurysm and the renal arteries. Suprarenal AAAs extend superiorly to include the orifices of the renal arteries to one or both kidneys. Juxtarenal AAAs are encountered four times more often than suprarenal AAAs. Pararenal AAAs, by definition, do not involve the superior mesenteric or celiac arteries and do not extend above the diaphragm to involve the thoracic aorta.
A, Anatomic diagram of a juxtarenal abdominal aortic aneurysm showing the aneurysm abutting the renal arteries. B, Suprarenal abdominal aortic aneurysm showing aneurysmal involvement of both renal arteries but not involving the superior mesenteric artery.
Pararenal AAAs account for 3% of all AAAs. Certain aspects of pararenal AAAs make them a challenge to treat, including the need for more extensive aortic dissection and the necessity for suprarenal clamping, with subsequent renal ischemia. Concomitant treatment of renal artery occlusive disease, which is commonly encountered in patients with pararenal AAAs, is a topic of separate discussion elsewhere in this text.
Presentation and Diagnosis
Men are more likely than women to have pararenal AAAs (2:1 ratio), though not to the same extent as with infrarenal AAAs (3.5:1 to 4:1 ratio). The increased affliction of women with pararenal AAAs, compared to infrarenal AAAs, may be caused by gender-related practice patterns, with a recognized delay in treating women until their AAAs become larger. This might contribute to a greater likelihood of aneurysmal changes in the more cephalic pararenal aorta. It is also possible that the loss of reproductive hormones following menopause—such as estrogen, that enhances elastin and collagen cross-linking—could contribute to a more generalized form of aortic dilation. If such is the case, then when infrarenal AAAs evolve in women, the juxtarenal aorta and suprarenal aorta are likely to also exhibit aneurysmal changes. Considerable anecdotal experience supports this contention, but definitive data to confirm this speculation are nonexistent.
The average age at diagnosis of pararenal AAAs is 67 years. Most pararenal AAAs exhibit extensive atherosclerosis. Currently, most pararenal AAAs are asymptomatic, being discovered during physical examinations or radiologic imaging for other illnesses. Pararenal AAAs are usually larger than infrarenal AAAs at the time of diagnosis.
Computed tomography arteriography (CTA) is preferred for imaging the anatomic character of pararenal aortic aneurysms and the adjacent aortic branches ( Figure 2 ). Reformatted three-dimensional reconstructions are most useful for developing a therapeutic plan. The risks of renal toxicity with large quantities of iodinated contrast during CTA studies must be carefully weighed in patients with preexisting renal insufficiency. Conventional biplanar catheter-based angiography, the standard in past decades for defining the anatomy of pararenal AAAs, continues to provide detailed information for clinicians, but it is used less often now because noninvasive imaging has improved.
Magnetic resonance angiography (MRA), enhanced by a breath-hold gadolinium technique, is another means of imaging the aortic anatomy with a high degree of accuracy. MRA can correctly identify the proximal AAA extent in nearly all patients, and it is very sensitive in recognizing splanchnic and renal artery stenoses greater than 50%.
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