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By Dr. Richard Cambria Expert April 12, 2011 – 10:08am

Abdominal Aortic Aneurysm – Case Study

by

Angela Rodriguez-Wong, MD, RVT, RPVI

Lois Eliassi, BS, RVT

http://www.navixdiagnostix.com/downloads/Navix%20-%20Q1%20’13%20Ultrasound%20Solutions.pdf

An aneurysm is defined as a focally dilated segment of an artery that is 1.5 times its normal diameter and involves all three arterial walls (intima, media and adventitia). Aneurysms can be found in the common femoral and popliteal arteries in the lower extremities, the splenic, mesenteric, and renal arteries in the abdomen, and also in the intracranial vessels. However, the most common is an abdominal aortic aneurysm (AAA) involving the aorta and iliac arteries.

Abdominal aortic aneurysms are generally asymptomatic and are discovered accidentally either by physician palpation or by a radiologic examination such as a chest or abdominal X-ray. The risk factors that increase the probability of developing a AAA are primarily smoking and family history. An abdominal aortic aneurysm can rupture and, according to the Centers for Disease Control and Prevention, ruptured AAA was the 10th leading cause of death in males between the ages of 65-74 in the United States in 2000.

The preferred method of screening for AAA is diagnostic ultrasound. According to the Journal of Vascular Surgery, diagnostic ultrasound performed by a registered vascular technologist has a sensitivity of 100 percent and a specificity of 96 percent for the detection of an infrarenal AAA. The abdominal aorta is considered aneurysmal when it measures >3.0 cm.

Because of its accuracy, diagnostic ultrasound not only has become an integral part in diagnosing AAA but is also an integral part in the evaluation of disease progression, the preoperative AAA evaluation, and the follow-up of AAA surgical repair. It is important to note that a rupture of an AAA is a surgical emergency and is difficult to evaluate with ultrasound due to the inability to easily demonstrate abdominal free fluid. If a rupture is suspected, it is recommended that other imaging modalities such as CT be employed to better demonstrate the ruptured aneurysm and any intra-abdominal free fluid.

Case Study – 

Abdominal Aortic Aneurysm – A 77 year-old male

Angela Rodriguez-Wong, MD, RVT, RPVI

Lois Eliassi, BS, RVT

Figure 1 Distal abdominal aortic aneurysm with mural thrombus.

Figure 2 Bifurcation of the aorta.

Case Study: A 77 year-old male with a past medical history of diabetes, hypertension, arthritis, aortic valve disease and heavy smoking was referred to Eastern Vascular Diagnostic Center with a 4.2 centimeter aneurysm. The patient denied any family history of aneurysm and is allergic to intravenous contrast. A physical exam found the patient alert with a blood pressure of 100/60 mmHg, a pulse of 58 and respiration of 16. Auscultation found a bruit in the left carotid artery, clear lungs, and a regular heart rhythm with an aortic systolic murmur. The patient had a well healed sub-costal incision on his abdomen. The physician was unable to palpate the aneurysms. The patient had an aortic valve replacement in 2007 and also a cholecystectomy. On May 12, 2012, a magnetic resonance imaging (MRI) scan without contrast was performed on the patient’s abdomen. The MRI found an AAA measuring greater than 3 cm with extensive plaque near the bifurcation. The aneurysm extended into the right common iliac artery (CIA) measuring 4.2 cm and into the left CIA measuring 3.1 cm. The MRI exam did not include the pelvis, so the extent of the iliac aneurysms was not clear. On July 31, 2012, the ultrasound was performed, demonstrating normal ankle brachial index (right-1.2, left-1.1) and a AAA measuring 3.9 cm which extended into the right and left CIA. The maximum diameter of the right CIA measures 4.1 cm with mural thrombus creating a residual lumen of 2.0 cm. The maximum diameter of the left CIA measures 4.3 cm, there is also mural thrombus noted but without significant appreciable diameter reduction within the vessel. A computed tomography (CT) scan of the abdomen and pelvis without contrast was performed on July 18th confirming the infrarenal AAA with extension into the iliac arteries bilaterally.

Surgery is recommended when an AAA reaches 5.0-5.5 cm in a male and 4.5-5.0 cm in females. Surgery, depending on the aneurysm, can be an open repair or an endovascular repair. In this patient, despite the size of the AAA being 4.1 cm, the disease also involved the bilateral common iliacs prompting the need for surgical intervention. The patient was cleared by cardiology and on July 31st had an AAA and bilateral Iliac aneurysm resection with a re-implantation of the inferior mesenteric artery and an Aorta to right Hypogastric bypass to maintain pelvic perfusion.

The U.S. Preventive Services Task Force has released a statement summarizing recommendations for screening for AAA. It states that screening benefits patients who have a relatively high risk for dying from an aneurysm; major risk factors are age 65 years or older, male sex, and smoking at least 100 cigarettes in a lifetime. The guideline recommends one-time screening with ultrasound for AAA in men 65 to 75 years of age who have ever smoked. No recommendation was made for or against screening in men 65 to 75 years of age who have never smoked, and it recommended against screening women. Men with a strong family history of AAA should be counseled about the risks and benefits of screening as they approach 65 years of age.

Angela Rodriguez-Wong, MD, RVT, RPVI 

awong@navixdiagnostix.com

Lois Eliassi, BS, RVT

leliassi@navixdiagnostix.com

Figure 3 Sagittal image of the right common iliac artery demonstrating the measurement of the aneurysm and the true lumen.

Figure 4 Coronal view of the left common iliac artery.

REFERENCES 

1. Anderson RN. Deaths: Leading causes for 2000. Natl Vital Stat Rep. 2002;50:1–85.

2. Kent KC, Zwolak RM, Jaff MR, et al. Screening for abdominal aortic aneurysm. J Vasc Surg. 2004;39:267–9.

3. Upchurch G Jr, Schaub T. Abdominal aortic aneurysm. American Family Physician. 2006;73(7), 1198-1204. http://www.aafp.org/afp/2006/0401/p1198.html

http://www.navixdiagnostix.com/downloads/Navix%20-%20Q1%20’13%20Ultrasound%20Solutions.pdf