A prospective study to define the optimum rescreening interval for small abdominal aortic aneurysm.

A prospective study of 99 patients with small abdominal aortic aneurysms was undertaken using serial ultrasound to assess the optimum screening interval. Fifty-three patients had aneurysms measuring 2.5-3.9 cm and 46 patients aneurysms of 4.0-4.9 cm. Aneurysms measuring 2.5-3.9 cm were screened annually and those > 4.0 cm every 6 months. There were eight deaths in the 2.5-3.9 cm group, none attributable to a ruptured aneurysm and five patients have had their aneurysm repaired. Nine patients died in the 4.0-4.9 cm group, one with a ruptured aneurysm measuring 5.6 cm at her previous screening visit and who was unfit for operation. No other patient had an aneurysm which ruptured between scans. There were seven elective repairs in this group. No patient died following elective operation in either group. The mean growth rate of aneurysms in the 2.5-3.9 cm group was 2.2 mm in the first year, 2.8 mm in the second and 1.8 mm in the third. Corresponding growth rates in the 4.0-4.9 cm group were 2.7 mm, 4.2 mm and 2.2 mm. This study supports a policy of annual screening for aneurysms measuring 2.5-3.9 cm and 6-monthly screening for those > or = 4.0 cm.