Renal and Mesenteric Aneurysms

Introduction

Aneurysms of the mesenteric circulation are a rare but potentially fatal pathology. Therefore, a thorough understanding of the natural history and treatment options available is critical to the vascular surgeon potentially faced with treating this entity. Successful treatment with standard open surgical techniques was first described in the 1950s. Since that time, a major paradigm shift toward endovascular treatment has occurred not unlike many vascular pathologies we commonly encounter. Furthermore, the quality of cross-sectional imaging has improved dramatically, which has led to more frequent incidental detection of mesenteric aneurysms. At the same time, technologic advances have made an increasing number of devices available for the treatment of mesenteric aneurysms. This chapter will cover the epidemiology of mesenteric aneurysm including incidence and standard treatment indications. We will focus primarily on contemporary endovascular treatment techniques, descriptions of currently available devices, and how to avoid common complications.

Background

Visceral artery aneurysms are defined as aneurysms involving the celiac artery, superior mesenteric artery, inferior mesenteric artery, or any branch of these arteries. Renal artery aneurysms are classified separately and discussed in the following section. Estimates of the true incidence of visceral artery aneurysms vary from as low as 0.1% to 2 % in adults. The proportionate distribution of visceral aneurysms is more clearly understood than the overall incidence and is as follows: 60% splenic artery, 20% hepatic artery, 5.5% superior mesenteric artery, 4% celiac artery, 4% gastric artery, jejunal, ilial, and colic arteries 3%, pancreaticoduodenal artery 2%, gastroduodenal artery 1.5%, and inferior mesenteric artery <1%. The traditional definition of aneurysms applies with aneurysm defined as 1.5 times the diameter of the normal nondilated vessel. Visceral aneurysms include a large proportion of degenerative fusiform aneurysms, pseudoaneurysms, and saccular aneurysms. Underlying etiologies are varied as well and include, atherosclerosis, medial degeneration, collagen vascular disease, fibromuscular dysplasia, infectious etiologies, inflammatory etiologies, vasculitis, iatrogenic injury, and trauma. In previous decades it was more common for mesenteric aneurysms to present ruptured, with associated mortality as high as 70%. Exact rates of mesenteric aneurysm rupture are still not well established, but with improved imaging quality more incidental nonrupture aneurysms are being discovered.

Congruent with the global trend in vascular surgery there is a shift towards endovascular treatment of mesenteric aneurysms as a first line option. This is secondary to advances in technology and an increasing array of devices available to practitioners. Standard open surgical techniques can certainly still be applied to intact or ruptured mesenteric aneurysms, but retrospective data have demonstrated equivalent survival between open and endovascular treatment for intact aneurysms and decreased morbidity with endovascular repair. Additionally, in the ruptured cohort endovascular treatment was shown to have significantly lower postoperative mortality (7.4% versus 28.6%). Therefore, the trend toward treatment with endovascular techniques is likely to continue. This chapter will describe available methods for each anatomic location, as well as generally accepted indications.

Indications

Treatment indications vary by anatomic location. For splenic aneurysms, indications are diameter greater than 2 cm, symptomatic, ruptured, pseudoaneurysm, pregnancy, child-bearing age, orthotopic liver transplant, and portal hypertension. Hepatic artery aneurysms are the next most common mesenteric aneurysm and treatment indications are ruptured, symptomatic, pseudoaneurysm, multiple aneurysms, polyarteritis nodosa, other inflammatory conditions, and size greater than 2 cm. Superior mesenteric aneurysms are less common, but all SMA aneurysms should be repaired in appropriate surgical candidates. Similarly, all celiac artery aneurysms, gastric, gastroepiploic, pancreaticoduodenal, gastroduodenal, inferior mesenteric, jejunal, ileal, and colic artery aneurysms should be repaired unless the patient is deemed too high risk with respect to comorbidities. Finally, mesenteric venous aneurysms can generally be safely observed unless they become symptomatic.