Can computed tomography scan findings predict "impending'' aneurysm rupture?

Several findings on computed tomography (CT) scans of intact aneurysms have been taken to suggest "imminent'' or "impending'' aneurysm rupture. Often these are identified incidentally in asymptomatic patients when an urgent operation was not planned and may even be ill advised. The authors evaluated whether these signs can truly predict short-term aneurysm rupture. A computerized medical archival system was reviewed from August 1994 to August 2004. Patients with aortic aneurysms and official CT scan reports of "impending rupture'' were reviewed. CT films and reports were reviewed for aneurysm characteristics, while computerized medical records were reviewed for patient demographics, comorbidities, symptoms, documented subsequent rupture, and operative findings. Signs of "impending rupture'' included the crescent sign, discontinuous circumaortic calcification, aortic bulges or blebs, aortic draping, and aortic wall irregularity. Rupture occurring within 2 weeks of the index CT was defined as supporting the "imminent'' label. Forty-five patients with aortic aneurysms and CT stigmata of "impending rupture'' were identified. Five patients with additional signs of suspicious leak and 1 with an infected previously repaired aneurysm were excluded. Of 39 intact aneurysms, 26 (67%) were infrarenal, 2 (5%) were suprarenal, and the remaining 11 (28%) were thoracoabdominal. The patient group had more women than expected (19/39, 49%) and larger aneurysms (mean diameter, 6.8 +/- 1.4 cm). Mean age was 74 years. Ten patients underwent elective repair within the first 2 weeks after the index CT scan (mean, 4 days), precluding adequate observation for early rupture. None had intraoperative signs of rupture. Early rupture: 2 of the 29 remaining patients ruptured within 72 hours of the CT scan, for a positive predictive value of 6.9%. One additional patient ruptured 7 months later after declining an early intervention. No Rupture: 26 patients were observed an average of 246 days (range, 14 days to 3 years) without evidence of rupture. Fourteen were repaired electively 2 weeks to 3 years after the index CT scan, and 12 never underwent repair, mostly because of severe associated comorbidities, and were observed a mean of 394 days without rupture. Although they should be taken seriously, CT signs of "impending rupture'' alone are poor predictors of short-term aortic aneurysm rupture, and alternative terminology is needed until better predictors can be identified.