Incidence, follow-up, and outcomes of incidental abdominal aortic aneurysms

Incidental abdominal aortic aneurysms (AAAs) are identified during imaging for other reasons. Incidental AAAs are important findings because they require monitoring and surgical treatment, when indicated, to prevent rupture. The prevalence of incidental AAAs and their management has not been extensively studied.

We electronically screened a 25% simple random sample of abdominal computed tomography (CT), ultrasound (US), and magnetic resonance imaging (MRI) studies conducted between 1996 and 2008 at one academic medical center. Screen-positive reports were manually reviewed to determine if they showed an incidental AAA. We reviewed the medical records of all in-patients to determine whether the incidental AAA was documented, a treatment plan was identified, and whether it was communicated to the patient's family physician through the discharge summary. We used evidence-based recommended schedules to determine the adequacy of AAA monitoring for each person.

In 79,121 abdominal images, we identified 812 incidental AAAs (1.0% of all studies) or 364 incidental AAAs annually (95% confidence interval [CI], 349-379). Patients were elderly (mean age, 74 years), and AAAs were a mean diameter of 4.0 cm. For 174 inpatients, AAAs were noted in only 51 patients (29%) and only 25 (15%) were communicated to the family physician. Of 329 patients who were observed beyond their first recommended follow-up scan, only 51 (16%) were monitored appropriately throughout their entire follow-up; the median proportion of follow-up time with recommended monitoring was 56% (interquartile range, 32%-82%). Elective AAA repair was done in 98 patients (13%), the probability of which was significantly increased when AAA monitoring frequency was compliant with that recommended in practice guidelines. Six patients (0.8%) were admitted with aortic rupture, the probability of which was independent of AAA monitoring.

Incidental AAAs are common and appear to be poorly monitored. Our data suggested that improved monitoring of incidental AAAs was independently associated with elective AAA repair. Population-based analyses are required to determine the influence that monitoring has on incidental AAA rupture and patient mortality.