AAA in medical terms stands for abdominal aortic aneurysm, a dangerous bulging of the body’s largest blood vessel where it passes through the abdomen. The aorta normally measures about 2 centimeters across in this area. When it swells to at least 1.5 times its normal size (typically 3 cm or more), it’s classified as an aneurysm. Most AAAs cause no symptoms and are discovered by accident during imaging for other conditions, but a rupture is a life-threatening emergency where roughly half of people die before reaching a hospital.
What Happens Inside the Aortic Wall
The aorta carries oxygen-rich blood from your heart down through your chest and abdomen, branching off to supply your organs, legs, and the rest of your lower body. Its wall is built from layers of structural proteins, primarily elastin and collagen, that keep the vessel strong and flexible under constant blood pressure.
In an AAA, those structural proteins gradually break down. The middle layer of the aortic wall thins and weakens, and autopsy studies consistently show chronic inflammation in the tissue, with immune cells infiltrating the damaged area. The section of aorta below the kidneys (the infrarenal segment) is especially vulnerable because it naturally has fewer of those reinforcing protein layers than the aorta in the chest. Over months and years, the weakened wall stretches outward like a worn spot on a tire, forming a balloon-like bulge that slowly expands.
Who Is Most at Risk
Smoking is the single biggest risk factor. People who have ever smoked are roughly three to five times more likely to develop an AAA than nonsmokers, and smoking is estimated to account for 75% of the excess prevalence of larger aneurysms (4 cm and above). Even people who quit 10 to 19 years earlier still carry nearly three times the risk of someone who never smoked. Duration of smoking matters more than the number of cigarettes per day.
Beyond smoking, the major risk factors include:
- Age: AAAs are most common in people over 65
- Sex: men are affected far more often than women, though women face higher rupture risk at smaller diameters
- High blood pressure: adds mechanical stress to an already weakened wall
- Family history: genetic factors play a role, particularly for aneurysms in the upper aorta
Symptoms and Warning Signs
Most abdominal aortic aneurysms are completely silent. You can have one for years without any indication. Some people notice a pulsing sensation near the navel, but this is uncommon with smaller aneurysms.
When an AAA is expanding rapidly or about to rupture, the classic signs are sudden, severe pain in the abdomen or lower back (often described as shooting pain) and a pulsating mass in the belly. This combination is a medical emergency. The pain can also radiate to the groin or legs, and people may feel lightheaded or go into shock from internal bleeding. Because symptoms only tend to appear when things are already critical, screening and monitoring are the main tools for catching AAAs before they become dangerous.
How AAAs Are Found
Ultrasound is the primary tool for detecting an AAA. It’s painless, uses no radiation, and picks up aneurysms with about 96% sensitivity and 97% specificity. For a screening exam, a technician simply runs a probe over your abdomen, and the test takes only a few minutes.
The U.S. Preventive Services Task Force recommends a one-time screening ultrasound for men aged 65 to 75 who have ever smoked. This is the group at highest risk and the one with the strongest evidence that early detection saves lives. When an aneurysm is found or needs detailed measurement before surgery, a CT scan provides the most precise picture of the size, shape, and anatomy of the bulge.
Monitoring a Small Aneurysm
Not every AAA needs surgery right away. Small aneurysms grow slowly and have a low risk of rupture, so the standard approach is regular ultrasound surveillance to track any changes. How often you go back for scans depends on the size:
- 3.0 to 3.4 cm: rescanned every three years
- 3.5 to 4.4 cm: rescanned every 12 months
- 4.5 to 5.4 cm: rescanned every three to six months
During this watch-and-wait period, quitting smoking is the most impactful thing you can do. Current smokers with a small AAA see their aneurysm expand about 0.35 mm per year faster than nonsmokers, and continuing to smoke doubles the risk of rupture regardless of the aneurysm’s size. Managing blood pressure and cholesterol also helps slow growth.
When Surgery Is Recommended
The widely used threshold for elective repair is 5.5 cm for men and 5.0 cm for women. At this size, the risk of rupture starts to outweigh the risks of the operation itself. Recent modeling research suggests the optimal thresholds may actually be higher for patients in average health (around 6.9 cm for a 60-year-old man and 6.1 cm for a 60-year-old woman), but 5.5 cm remains the standard trigger for surgical evaluation in most clinical guidelines.
Rupture risk climbs steeply with diameter. For aneurysms between 5.5 and 5.9 cm, roughly 9% rupture within a year. Between 6.0 and 6.9 cm, that rises to about 10% overall, with the 6.5 to 6.9 cm subgroup reaching 19%. At 7.0 cm and above, the one-year rupture rate is around 33%. Once an aneurysm reaches 8.0 cm, about one in four ruptures within six months.
Types of Repair
There are two surgical approaches to fixing an AAA, and the choice between them depends largely on the aneurysm’s shape, location, and the patient’s overall fitness.
Open Surgical Repair
The traditional method involves a large incision in the abdomen. The surgeon clamps the aorta above and below the aneurysm, cuts out the weakened section, and sews in a synthetic graft to replace it. This is a major operation with a longer recovery, typically requiring several days in intensive care and a hospital stay of about a week, followed by weeks of limited activity at home. Cardiac complications occur in roughly 20 to 22% of open repair patients, and pulmonary complications in about 16%.
Endovascular Repair (EVAR)
The less invasive option threads a collapsed fabric-and-metal graft through small incisions in the groin arteries and positions it inside the aneurysm using X-ray guidance. The graft lines the weakened section from the inside, redirecting blood flow away from the bulging wall. Recovery is significantly faster, with shorter hospital stays and less pain. Cardiac complications drop to about 11%, and lung complications fall to around 3%.
The tradeoff: EVAR patients are more likely to need follow-up procedures down the line. Long-term studies at six to eight years show that survival rates between the two approaches even out, but EVAR carries higher rates of graft-related complications over time, requiring ongoing imaging surveillance to ensure the graft stays properly sealed.
What Happens if an AAA Ruptures
A ruptured AAA is one of the most lethal surgical emergencies. About 50% of people die before they ever reach a hospital, and the overall mortality rate, including those who never make it to an operating room, is estimated at 80 to 90%. Among patients who do undergo emergency repair, roughly 42% do not survive to discharge. Emergency endovascular repair, when anatomically feasible, has been associated with a 79% reduction in mortality and 51% fewer complications compared to emergency open surgery. Still, even the best-case scenario for a rupture carries far higher risk than elective repair, which is why detection and monitoring before that point matters so much.