An aneurysm is a localized, abnormal bulging in the wall of a blood vessel. This weakening allows blood pressure to push the arterial wall outward. Visceral artery aneurysms are a less common type that specifically affect arteries supplying blood to abdominal organs, including the spleen, liver, kidneys, and intestines. Despite their rarity, these aneurysms carry a risk of rupture.
What is a Visceral Artery Aneurysm?
A visceral artery aneurysm is a weakened area in the wall of an artery within the abdomen, defined as an expansion exceeding 50% of the artery’s normal diameter. These aneurysms can develop in any artery supplying the abdominal organs, including the intestines, kidneys, liver, pancreas, spleen, and stomach.
The most frequently encountered type is the splenic artery aneurysm, accounting for approximately 60% to 80% of all visceral artery aneurysms. Hepatic artery aneurysms are the second most common, making up about 20% of cases, followed by superior mesenteric artery aneurysms at around 5% to 5.5%.
Why Visceral Artery Aneurysms Develop
Visceral artery aneurysms arise from various underlying conditions that compromise the structural integrity of arterial walls. Atherosclerosis, characterized by plaque buildup and hardening of the arteries, is a common contributing factor. Connective tissue disorders, such as fibromuscular dysplasia, Marfan syndrome, and Ehlers-Danlos syndrome, can also predispose individuals to these aneurysms by weakening arterial tissue. Fibromuscular dysplasia, for instance, can cause an appearance described as a “string of beads” in the artery due to alternating narrowings and dilations.
Other causes include inflammation of the blood vessels, known as vasculitis, and certain infections that can directly damage artery walls. Trauma, such as an injury or complications from abdominal surgery, can lead to the formation of pseudoaneurysms, which are collections of blood outside the arterial wall rather than a true bulging. Conditions like pancreatitis are also associated with the development of pseudoaneurysms in nearby arteries.
Identifying Visceral Artery Aneurysms
Visceral artery aneurysms are often asymptomatic and frequently discovered incidentally during medical imaging for unrelated conditions. When symptoms do occur, they indicate the aneurysm has grown to a significant size or is pressing on adjacent structures. Such symptoms can include abdominal pain, nausea, vomiting, or weight loss. Occasionally, a large aneurysm might be felt as a pulsating mass in the abdomen.
When a visceral artery aneurysm is suspected, various imaging techniques are used for diagnosis and assessment. Computed tomography angiography (CTA) and magnetic resonance angiography (MRA) provide detailed images of blood vessels and measure the aneurysm’s diameter. Conventional angiography, a more invasive procedure, involves injecting a contrast dye into the arteries to visualize their structure, which helps confirm the presence of an aneurysm and assess blood flow. Ultrasound examinations can also detect these aneurysms and are often the initial screening tool.
Managing Visceral Artery Aneurysms
The management of visceral artery aneurysms depends on several considerations, including the aneurysm’s size, location, presence of symptoms, and the patient’s overall health. For small, asymptomatic aneurysms, particularly those less than 2 centimeters in diameter, a strategy of watchful waiting is recommended. This involves periodic monitoring with imaging tests to detect any growth or changes over time. Splenic artery aneurysms may be monitored until they reach 3 centimeters before intervention is considered.
When intervention becomes necessary, endovascular repair is a common minimally invasive approach. This technique involves inserting a catheter into an artery, usually in the groin, and guiding it to the aneurysm. Coiling, where platinum coils are deployed to fill the aneurysm sac and promote clotting, or stent placement, which involves using a mesh tube to reinforce the weakened arterial wall, are common endovascular methods. This approach leads to shorter hospital stays compared to open surgery.
Open surgical repair remains an option, especially for complex cases where endovascular methods are not suitable or have been unsuccessful. Surgical techniques can include ligating (tying off) the aneurysm, performing an aneurysmorrhaphy (repairing the aneurysm while preserving blood flow), or resecting the aneurysm and reconstructing the artery with a bypass graft. The primary goal of any intervention is to prevent rupture, the most severe complication. Pseudoaneurysms, due to their higher risk of rupture, are often treated regardless of their size.
Serious Outcomes
The most serious outcome associated with a visceral artery aneurysm is its rupture, which constitutes a medical emergency. A ruptured aneurysm leads to severe internal bleeding, potentially causing shock and a significant drop in blood pressure. This life-threatening event can result in death if not addressed immediately.
Signs and symptoms of a ruptured visceral artery aneurysm include sudden, intense abdominal pain, dizziness, a rapid heart rate, and low blood pressure. The specific presentation can vary depending on the affected artery and where the bleeding occurs, sometimes leading to symptoms like bloody vomit or bloody stools. The mortality rate associated with a ruptured visceral artery aneurysm can range from 10% to 25%, and in some instances, it can be as high as 76%. For pregnant women, rupture carries an even higher risk, with maternal mortality rates potentially reaching 70% to 75% and fetal mortality rates exceeding 90%.