Aneurysm vs Pseudoaneurysm
Both aneurysm and pseudoaneurysm present the same. Both present as pulsatile, painful masses. There may be reddening around both. Because of the similar presentation, differentiation is difficult at first glance. However, there are many fundamental differences between aneurysm and pseudoaneurysm and that will be discussed here in detail, highlighting the clinical features, symptoms, causes, investigation and diagnosis, prognosis, and treatment of each condition.
Aneurysm is an abnormal dilatation of an artery. Aneurysm may be fusiform or sac-like. Aorta, iliac arteries, femoral and popliteal arteries are the common sites. Occlusion of the arterial lumen due to atheroma is the principle cause of proximal arterial dilation. In certain connective tissue diseases like Marfan’s, Ehlers-Danlos syndrome, there is extensive pliability of vessel walls leading to pathological spontaneous dilatation. Infections like endocarditis and tertiary syphilis are also known to cause aneurysms.
Most aneurysms resolve spontaneously with thrombosis, but some aneurysms may rupture causing extensive life threatening bleeding. Rupture is rare in dilated arteries with a diameter less than 5 cm. Beyond 5cm, the risk of rupture increases exponentially. Early arterial dilatation may exert pressure on surrounding structures. (Ex: abdominal aortic aneurysm may press on ureter, duodenum, and lumbar spine). Rupture results in a sudden onset severe pain and blood pressure drop. It may mimic renal colic, but immediate diagnosis and operation is life-saving. Fistula formation is a known result of aneurysm rupture. Sometimes blood clots formed inside an aneurysm may break off and embolize.
Ultra sound scan and CT scan are diagnostic. When the aneurysm is less than 5 cm in diameter, regular observation, control of blood pressure, and bed rest are vital. Regular assessment of aneurysm diameter is essential. Symptomatic aneurysms and aneurysms larger than 5 cm need operative treatment. In elective cases, CT scan is helpful in defining the proximal extent in relation to the renal arteries. Operation involves clamping the aorta below the renal arteries and clamping the iliac arteries distal to the aneurysm. The aneurysm sac is opened longitudinally, and aortic segment is replaced with either a straight or a bifurcated synthetic graft. The graft is laid inside the aneurysm, which is then closed over it. Another method involves passing a synthetic graft endoluminally through the femorals. Operative mortality of ruptured aneurysms remains around 50%.
Pseudo-aneurysms literally mean false aneurysms. It is a result of blood leakage after trauma. Blood collects outside the artery and the surrounding tissue walls it off. Pseudo-aneurysms usually present as pulsatile, painful and slow expanding masses. Because there is reddening, they are commonly confused with abscesses.
There may be a history of catheterization or other invasive vascular instrumentation. CT scan and duplex ultrasound are diagnostic. Although pseudo-aneurysms can occur anywhere in the body, femoral and radial, ulnar and brachial pseudo-aneurysms have become common because of cardiac catheterization and arterio-venous fistula formation for hemodialysis.
Treatment methods are covered stents, probe compression, thrombin injection and surgical ligation. Covered stenting involves the introduction of a small stent endoluminally to exclude the expanding hematoma from the circulation. There is usually a small circulation into and out of the pseudo-aneurysm which can be seen with ultrasonography. The probe can be pressed against the neck of the expanding hematoma for about 20 minutes. When the probe is removed, there is no further circulation because the blood inside the pseudo-aneurysm clots during those 20 minutes. This method is known as ultrasound probe compression. Thrombin is a clotting agent which can be injected into the pseudo-aneurysms under ultrasound guidance. Direct surgical ligation of the neck of the expanding hematoma is another treatment option.
What is the difference between Aneurysm and Pseudoaneurysm?
• Aneurysm is a dilatation of the artery while pseudo-aneurysm is a walled off collection of blood outside a damaged artery.
• Aneurysm and pseudo-aneurysms can both expand, but pseudo-aneurysms do not rupture with dilatation.
• Mortality of aneurysms is much higher than that of pseudo-aneurysms.