Residency · Residency · Interventional Radiology

Visceral Artery Aneurysm Embolization

Overview

Visceral artery aneurysms (VAAs) are uncommon but clinically important because of their rupture potential. A true aneurysm involves all three layers of the arterial wall, whereas a pseudoaneurysm is a contained rupture in which the wall consists only of adventitia or surrounding tissue, conferring a significantly higher rupture risk. The overall incidence is 0.1-2% in autopsy series, with detection rates increasing due to widespread use of cross-sectional imaging.

Distribution by Artery

The splenic artery accounts for approximately 60% of all VAAs, making it by far the most common site. The hepatic artery is next at 20%, followed by the superior mesenteric artery at 5-8%, the celiac artery at 4%, gastric and gastroepiploic arteries at 4%, renal artery at 3%, and pancreaticoduodenal/gastroduodenal arteries at 2-3%. Jejunal, ileal, and colic branches collectively account for less than 2%.

Splenic Artery Aneurysm (SAA)

Epidemiology and Risk Factors

The splenic artery aneurysm is the most common VAA and has a notable female predominance with an F:M ratio of 4:1. Key associations include multiparity, portal hypertension, medial fibrodysplasia, and liver transplant. Most are discovered incidentally on CT or ultrasound.

Rupture Risk and Indications for Treatment

The overall rupture risk for true splenic artery aneurysms is 2-3%. However, rupture risk increases dramatically during pregnancy, with up to 25% maternal mortality and 75% fetal mortality reported. Treatment is indicated when the diameter exceeds 2 cm (some advocate a threshold of 3 cm given the low rupture rate), for any size in women of childbearing potential, for any pseudoaneurysm regardless of size, for symptomatic aneurysms, and for documented growth on serial imaging.

Embolization Technique

Access is transfemoral with selective catheterization of the celiac trunk and then the splenic artery. Sac packing involves deploying coils within the aneurysm sac and is preferred when feasible. The exclusion or sandwich technique involves embolizing the splenic artery both distal to and proximal to the aneurysm, trapping the sac, and is preferred for saccular or wide-neck aneurysms. Stent-graft exclusion places a covered stent across the aneurysm neck to maintain in-line splenic artery flow, though this is technically challenging because of the tortuous course of the splenic artery. Post-embolization splenic infarction may occur but is usually clinically insignificant if distal collateral flow through the short gastric arteries is maintained. The risk of overwhelming post-splenectomy infection is negligible with coil embolization because the spleen typically maintains viability via these collaterals.

Hepatic Artery Aneurysm

Key Considerations

The hepatic artery aneurysm is the second most common VAA. Eighty percent are extrahepatic, occurring in the common hepatic, proper hepatic, or bifurcation, while 20% are intrahepatic at the segmental or subsegmental level. The rupture risk is higher than that of splenic artery aneurysms, with figures of 20-40% reported in surgical series, though these are likely overestimated. Rupture may present as hemobilia (bleeding into the bile duct), hemoperitoneum, or gastrointestinal hemorrhage.

Treatment

The repair threshold is greater than 2 cm or any pseudoaneurysm. Maintaining hepatic arterial flow is desirable when possible, though the portal vein supplies 75% of hepatic blood flow, so hepatic artery sacrifice is usually tolerated provided the portal vein is patent. Embolization with coil exclusion and sacrifice of the involved hepatic branch is performed after confirming portal vein patency. A stent-graft placed across the aneurysm preserves hepatic flow and is preferred when anatomy allows. If the portal vein is thrombosed or stenotic, hepatic artery sacrifice may cause hepatic ischemia or infarction.

SMA and Celiac Artery Aneurysms

These are less common but carry higher mortality with rupture. SMA aneurysms are often mycotic (infected) or associated with pancreatitis. Treatment involves coil embolization with flow preservation via collaterals, or stent-graft placement when possible. Downstream bowel perfusion must be considered because sacrifice of the SMA trunk is poorly tolerated. Celiac aneurysms are rare and treated similarly with coil exclusion or stent-graft.

Pseudoaneurysms

Etiologies

Pancreatitis is the most common cause of visceral pseudoaneurysms, with enzymatic digestion of the arterial wall commonly involving the gastroduodenal, pancreaticoduodenal, and splenic arteries. Trauma, both blunt and penetrating, is another important cause. Iatrogenic pseudoaneurysms arise after surgery (hepatic artery after cholecystectomy or liver transplant) or after biopsy. Infection can produce mycotic aneurysms.

Management Principles

All pseudoaneurysms should be treated regardless of size because they lack a true wall and carry a high rupture rate. Embolization is first-line for most visceral pseudoaneurysms. For end-organ arteries (such as intrahepatic branches), the approach is to embolize both proximal and distal to the pseudoaneurysm using the front-door and back-door technique. For in-line arteries (such as the SMA trunk), a stent-graft is used to preserve flow. Direct percutaneous thrombin injection may be employed for select pseudoaneurysms, such as those occurring after liver biopsy.

Embolic Agents for VAA

Coils

Coils are the most commonly used agents, providing mechanical occlusion. They come in pushable or detachable configurations and are size-matched to the target vessel. They are preferred for sac packing and exclusion techniques.

Liquid Embolics

N-butyl cyanoacrylate (NBCA or glue) polymerizes on contact with blood and is particularly useful for emergent embolization of pseudoaneurysms when rapid occlusion is needed. Onyx and PHIL are ethylene vinyl alcohol copolymer agents that offer slower, more controlled delivery and are used in select cases.

Vascular Plugs

The Amplatzer vascular plug enables precise deployment in larger vessels and is useful for proximal occlusion of the splenic artery.

Covered Stent-Grafts

Devices such as the Viabahn, iCAST, or BeGraft preserve flow through the parent artery while excluding the aneurysm. Their application is limited by vessel tortuosity and small caliber.

Surveillance

Post-treatment imaging with CTA or duplex ultrasound is performed at 1, 6, and 12 months, then annually, assessing for sac shrinkage, endoleak in stent-graft cases, and reperfusion. Untreated small true aneurysms under 2 cm are followed with surveillance imaging every 6-12 months.

<image>Anatomic illustration showing the distribution of visceral artery aneurysms. An anterior view of the abdominal vasculature with the celiac trunk, SMA, and IMA branches labeled. Color-coded circles indicate the relative frequency of aneurysms at each location: large circle at the splenic artery (60%), medium circle at the hepatic artery (20%), and small circles at the SMA (5-8%), celiac (4%), renal (3%), and gastroduodenal/pancreaticoduodenal arteries (2-3%). An inset shows the difference between a true aneurysm (all three vessel wall layers intact) and a pseudoaneurysm (contained by adventitia or perivascular tissue only).</image>

<image>Illustration of splenic artery aneurysm embolization techniques. Three panels: (1) Sac packing technique showing coils deployed within the aneurysm sac through a microcatheter, with the splenic artery remaining patent; (2) Exclusion (sandwich) technique showing coils placed distal to and proximal to the aneurysm, trapping the sac, with collateral flow to the spleen via short gastric arteries indicated by arrows; (3) Stent-graft exclusion showing a covered stent deployed across the aneurysm neck preserving in-line splenic artery flow. Each panel includes a small inset showing the post-treatment angiographic result.</image>

<image>Angiographic images of visceral pseudoaneurysm embolization in the setting of pancreatitis. Three panels: (1) Celiac angiogram showing a pseudoaneurysm of the gastroduodenal artery with an irregular, lobulated sac adjacent to the pancreatic head; (2) Selective microcatheter positioned distal to the pseudoaneurysm with coils deployed for back-door embolization; (3) Completion angiogram after proximal (front-door) coil embolization showing complete exclusion of the pseudoaneurysm with no residual filling. The pancreaticoduodenal arcade collateral pathway is labeled.</image>

Clinical Pearls

All pseudoaneurysms should be treated regardless of size because they lack a true wall and carry high rupture risk. For splenic artery aneurysms, women of childbearing potential should be treated at any size due to the catastrophic rupture risk during pregnancy. Before sacrificing the hepatic artery, portal vein patency must be confirmed because hepatic artery occlusion is well-tolerated only if portal flow is intact. The sandwich or front-door/back-door embolization technique is critical for pseudoaneurysms, as embolizing both inflow and outflow prevents back-bleeding. Pancreatitis is the most common cause of visceral pseudoaneurysms, and a high index of suspicion should be maintained in patients with pancreatitis who develop hemodynamic instability or a drop in hemoglobin. Covered stent-grafts preserve flow but are limited by vessel tortuosity, especially in the splenic artery.

References

• Defined by the Defined by the SIR Guidelines on Management of Visceral Artery Aneurysms. J Vasc Interv Radiol 2020
• Defined by the CIRSE Standards of Practice on Visceral Artery Aneurysm Embolization. Cardiovasc Intervent Radiol 2021
• Defined by the Defined by the SVS Clinical Practice Guidelines on Visceral Aneurysms. J Vasc Surg 2020
• Defined by the Defined by Defined by Pulli R et al. Visceral artery aneurysms: a review. J Cardiovasc Surg 2019

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