DIAGNOSIS OF SMALL INFRARENAL AORTIC-ANEURYSMS BY ULTRASONOGRAPHY

Objective. Localized dilatation of the infrarenal aorta is currently a ssessed by comparison with the suprarenal aorta using a diameter ratio >1.5 as an index of aneurysm. However, the bulging may be underestima ted when there is concomitant enlargement of the suprarenal aorta and enhanced tapering of the aorta toward the bifurcation. Therefore, we s tudied an alterantive reference point closer to the aneurysm. Experime ntal design. Prospective ultrasound study of localized infrarenal aort ic dilatation where its diameter is compared to 1) suprarenal aorta ju st above the orifices of the renal arteries and (2) infrarenal aorta a t the upper margin of the aortic dilatation. Patients. 91 consecutive ambulatory patients (66 men and 25 women, mean age 69 yrs) with a loca lized infrarenal aortic dilatation of greater than or equal to 3.0 cm in diameter. Results. Mean diameter of the aortic bulges was 4.5+/-0.1 3 (SD) cm in males vs 4.0+/-0.73 cm in the females, (NS). The diameter ratio dilatation/suprarenal aorta exceeded 1.5 in 96% of the patients with an aortic bulging greater than or equal to 4.0 cm (n=53) as comp ared to only 55% when the diameter was 3.0 to 3.9 cm (n=38), p<0.0001. However, when the aorta immediately above the dilated part was used a s size reference the number of aortic bulges with a relative size of > 1.5 increased from 55% to 87% (p<0.001). Conclusions. The degree of ao rtic bulging may be understimated when the diameter of the dilated are a is compared to that of the suprarenal aorta instead of the aorta imm ediately proximal to the dilatation, especially in small dilatations l ocated near the aortic bifurcation.