During a routine physical examination, a family physician identifies an asymptomatic pulsatile abdominal mass in a 62-year-old man. The ultrasound evaluation that followed demonstrated a 4.2-cm aneurysm in the infrarenal aorta. This patient is subsequently referred to you for evaluation and management. His past medical history is significant for hypertension and stable angina. He has a history of 40 packs a year of cigarette smoking. His current medications include aspirin, a β-blocker, and nitrates. The patient describes himself as an active man who is retired and plays 18 holes of golf twice a week. On examination, the carotid pulses and upper extremity pulses are found to be normal. The abdomen is nontender with a prominent aortic pulsation. Pulses in the femoral and popliteal regions are easily palpated and appear more prominent than usual.
What are the complications associated with this disease process?
What is the best treatment?
ANSWERS TO CASE 29: Abdominal Aortic Aneurysm
Summary: A 62-year-old reasonably healthy man presents with an asymptomatic 4.2-cm abdominal aortic aneurysm (AAA).
• Complications: Rupture, thrombosis, distal embolism, and other peripheral aneurysms.
• Best treatment: The best treatment for this patient is debatable. The risk of complications from the aneurysm must be weighed against the risk of surgical or endovascular intervention.
1. Learn the presentation, evaluation, treatment, and follow-up of patients with aneurysms.
2. Learn the risks and outcomes associated with elective open aneurysm repair, elective endovascular repair, and the repair of ruptured aneurysms.
A relatively healthy 62-year-old man presenting with a 4.2-cm AAA can be observed with serial examinations and repeated ultrasonography or undergo elective aneurysm repair. The most important reason for AAA repair is to prevent aneurysm rupture, which is almost uniformly a fatal event. The risks and benefits of the options must be discussed with the patient. If the patient wishes to undergo elective repair, a thorough evaluation to assess other comorbidities should be undertaken. Two large randomized controlled clinical trials have compared surveillance versus prophylactic surgery for patients with asymptomatic AAA less than 5.5 cm, and both trials demonstrated no advantages to prophylactic repairs; the only limitation to these trials was that relatively few women were included.
APPROACH TO: Abdominal Aortic Aneurysm
More than 95% of AAAs develop as complications of atherosclerosis, and more than 90% are infrarenal. Many are found asymptomatically, but some can cause distal emboli or pain. Others are found in association with other peripheral (ie, popliteal and femoral) aneurysms. The majority of AAAs are detected asymptomatically. An AAA is a disease where size matters. Because of the relationship between AAA size and the risk of rupture, the maximal diameter is an important discriminant in assessment and management. The law of Laplace (wall tension is proportional to the square of the radius and the inverse of wall thickness) provides the physics behind the pathophysiology of AAA rupture. The rupture rate for asymptomatic aneurysms less than 5 cm is 0.6% per year. Once an AAA reaches 5 cm in diameter, the risk of rupture is 5% to 10% per year. At 6 cm it rises to 10% to 20% per year, and at 7 cm the rupture risk is 20% to 30% per year.
Surgical risk of patients for aneurysm repair can be stratified based on patient age, functional status, cardiac risk, pulmonary risk, renal risk, and other systemic illnesses (liver disease, malignancies, diabetes). Patients can be stratified as low, intermediate, or high risk based on these factors. Risk modification strategies including the initiation of perioperative β-blocker and statin therapy may be considered appropriate in addition to lifestyle modifications, such as smoking cessation. High-risk individuals with AAAs should be referred to a vascular surgery specialist for consideration of endovascular repair.
Repair of a ruptured AAA can be attempted in only half of patients because others never reach the hospital alive. Even today, 40% to 60% of patients with a ruptured AAA do not survive emergency surgery. Because good-risk patients have a mortality rate of 1% to 3% when undergoing elective surgery, the usual criterion for recommending repair is when an AAA reaches 5.5 cm in men and 5.0 cm in women. However, as AAAs arise in patients with atherosclerosis, there is a significant association with other risks and comorbidities that can complicate repair. Cardiac complications remain the most common cause of perioperative morbidity and mortality.
AAAs found on routine examination should have their size confirmed by an imaging study. Ultrasound is inexpensive and safe but not as reproducible over time. Computed tomography scanning requires radiation exposure but can give enough information to assess suitability for endovascular aneurysm repair (EVAR) or conventional open surgery. Arteriography cannot diagnose an AAA because it only delineates the lumen of a vessel. However, a preoperative angiogram helps in operative planning for both EVAR and open repairs. Open repair has withstood the test of time, but because of increased perioperative morbidity and mortality associated with this approach, most centers now consider EVAR as the preferred approach. Patients with a higher risk for open repair complications (severe coronary artery disease, chronic obstructive pulmonary disease, obesity, malignancy, adhesions, and others) can be offered protection from rupture with EVAR. One must realize that EVAR currently has a risk of rupture of 0.7% to 1.0% per year (according to the EURO-STAR [EUROpean collaborators on Stent-graft Techniques for abdominal aortic Aneurysm Repair] Registry). In addition, because of technical issues in EVAR, following EVAR the patient requires intensive imaging follow-up every 3 to 6 months. Because of associated risk profiles, the ultimate perioperative patient mortality for EVAR is still in the 2% to 3% range. The periprocedural cardiovascular, pulmonary, and infectious complication rates associated with EVAR are significantly lower than the complications associated with open repairs. Endoleaks are minor leaks that can occur following EVAR. A type IA endoleak is a leak around the proximal aortic neck. Type IB endoleak is a retrograde leak from the iliac artery. Type II endoleaks are the most common type and occur as the result of retrograde flow from the inferior mesenteric artery or lumbar artery into the aneurysm sac. Type III endoleaks are leakage at the endograft overlap sites or from the grafts themselves. Type IV endoleaks are related to continued leakage of fluid through the graft material even without any definitive openings. Endoleaks are amendable to additional interventions and are not associated with patient mortality. The occurrences of endoleaks requiring repeat interventions have significantly decreased (~10%) as the technology and expertise associated with EVAR has accumulated over the past 15 years. The actual recommendation for EVAR versus open AAA repair should be made by a trained vascular specialist well versed in both techniques.
For a patient who presents with AAA rupture (back pain, hypotension, and a pulsatile epigastric mass), operative open repair is the most available and most potentially lifesaving therapy. If AAA rupture is clinically suspected, the patient should undergo emergent operative repair. There is no role for radiologic imaging if the clinical impression is a ruptured AAA—the delay involved in obtaining imaging is too risky for the patient as compared to a potentially negative exploration.
29.1 A 58-year-old man is found on physical examination to have an AAA. He has no symptoms. Ultrasound reveals that it is 4 cm in diameter. Which of the following is considered appropriate surveillance for this patient?
A. Observation with yearly ultrasound
B. Percutaneous graft replacement
C. Angiography every 6 months
D. Aortofemoral bypass surgery
29.2 In which of the following conditions is conservative management indicated in the patient described at the beginning of the case?
A. Presenting 11 months later with an AAA that is 5.5 cm in size.
B. Unexplained back pain in a 4.2-cm aneurysm and normotensive.
C. Bilateral embolization to all his toes.
D. Presenting 3 years later with shock and severe abdominal pain.
E. AAA is 4.3 cm on ultrasound 2 years later.
29.3 Which of the following is a complication associated with abdominal aortic aneurysms?
A. Early satiety
B. Colonic obstruction
C. Painful discoloration of the great toe
29.4 Which of the following statements is most accurate regarding EVAR?
A. EVAR requires more intensive postprocedural follow-up than open repairs.
B. Perioperative complications associated with EVAR and open repairs are identical.
C. EVAR is an inferior approach for patients with prior intra-abdominal operations.
D. EVAR application is no longer indicated based on its complication profile.
29.5 For which of the following patients is nonoperative management most appropriate?
A. A 63-year-old petite woman with an asymptomatic 5.2-cm AAA.
B. A 96-year-old man with severe dementia and a 6-cm AAA. The patient has been a long-term resident of a chronic care facility due to the inability to ambulate or perform activities of daily living.
C. A 63-year-old man with a 5.3-cm AAA who has developed unexplainable back pain and abdominal pain over the past several days.
D. A 61-year-old man with a 5.3-cm AAA and recent onset of pain and ecchymosis in the tips of several of his toes on both feet.
29.1 D. Yearly ultrasound is part of conservative protocol for the follow-up of patients with AAA. The choice of ultrasound or CT for the imaging depends on which is more available in one’s practice environment.
29.2 E. The patient in choice D is presenting with a rupture. The patient in choice B is the most controversial candidate for operative repair; however, if a complete workup cannot find another cause of back pain, the AAA must be implicated and strong recommendations for repair should be made.
29.3. D. Most AAAs are asymptomatic. Patients may have abdominal discomfort or back pain. Rarely, aneurysmal erosion into a ureter may be seen, leading to gross hematuria. Rupture should be suspected with increasing abdominal or back pain with hypotension. Mortality exceeds 50% with AAA rupture. Ischemia of the lower extremity may occur but will involve more than the great toe.
29.4 A. EVAR is an approach that is associated with lower perioperative cardiopulmonary complications in comparison to open aneurysm repairs; however, as the result of continued enlargement of the aorta and migration of the device, leakage around the device can occur following EVAR. With appropriate surveillance, endoleaks are often successfully managed with minimal risk of mortality from rupture. EVAR offers advantages over open repair especially in patients with potential “hostile abdomen” from prior abdominal operations or other unrelated intra-abdominal pathology.
29.5 B. The risk of rupture with his 6-cm AAA is approximately 10% to 20% per year, and EVAR may offer protection against rupture and may improve the longevity of this patient. However, in this individual with advanced age and an extremely poor quality of life, a prophylactic operation to extend his life presents a difficult ethical dilemma. Performing an expensive intervention to prolong the life of this individual also constitutes poor allocation of medical resources. The patient described in choice A fits the size criteria for elective repair. The presentation of patient in choice C suggests symptoms related to his aneurysm that could indicate increased risk of rupture. The patient presentation in choice D is consistent with embolic disease associated with AAA, or the “blue toe syndrome.”
Patients diagnosed with an AAA should have a thorough pulse examination to look for associated aneurysms in the periphery and/or concomitant occlusive disease.
AAAs are palpated in the epigastrium; iliac aneurysms are palpated in the infraumbilical position.
An AAA greater than 5.5 cm in a man and greater than 5.0 cm in a woman is at increased risk for rupture and should be considered for elective repair.
In the case of a suspected rupture, negative laparotomy findings are much better than delay in control of the AAA in the operating room.
Foley PJ, Fairman RM. Endovascular treatment of abdominal aortic aneurysm. In: Cameron JL, Cameron AM, eds. Current Surgical Therapy. 10th ed. Philadelphia, PA: Mosby Elsevier; 2011:704-709.
Lin PH, Kougias P, Bechara C, Cagiannos C, Huynh TT, Chen CJ. Arterial disease. In: Brunicardi FC, Andersen DK, Billiar TR, et al, eds. Schwartz’s Principles of Surgery. 9th ed. New York, NY: McGraw-Hill; 2010:701-775.
Patel VI, Cambria RP. Open repair of abdominal aortic aneurysms. In: Cameron JL, Cameron AM, eds. Current Surgical Therapy. 10th ed. Philadelphia, PA: Mosby Elsevier; 2011:695-704.