Diagnosis of small infrarenal aortic aneurysms by ultrasonography

Localized dilatation of the infrarenal aorta is currently assessed by comparison with the suprarenal aorta using a diameter ratio > 1.5 as an index of aneurysm. However, the bulging may be underestimated when there is concomitant enlargement of the suprarenal aorta and enhanced tapering of the aorta toward the bifurcation. Therefore, we studied an alternative reference point closer to the aneurysm.

Prospective ultrasound study of localized infrarenal aortic dilation where its diameter is compared to 1) suprarenal aorta just above the orifices of the renal arteries and (2) infrarenal aorta at the upper margin of the aortic dilatation.

91 consecutive ambulatory patients (66 men and 25 women, mean age 69 yrs) with a localized infrarenal aortic dilatation of > or = 3.0 cm in diameter.

Mean diameter of the aortic bulges was 4.5 +/- 0.13 (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 > or = 4.0 cm (n = 53) as compared 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 as size reference the number of aortic bulges with a relative size of > 1.5 increased from 55% to 87% (p < 0.001).

The degree of aortic bulging may be underestimated when the diameter of the dilated area is compared to that of the suprarenal aorta instead of the aorta immediately proximal to the dilatation, especially in small dilatations located near the aortic bifurcation.