Figure 1. Modified Brewster classification of disease of the upper and lower limb. (a) Type 1 disease: involving the aortoiliac vessels in the lower limb, and the aortic arch and great vessels in the upper limb. (b) Type II disease: aorta to external iliac or femoral arteries (lower limb), or aorta to axillary arteries (upper limb). (c) Type III disease: multilevel disease in the upper and lower limbs. (d) Type IV disease: vessels above the knee or elbow are normal but vessels below the knee or elbow are diseased.