. Author manuscript; available in PMC: 2017 Oct 25.

Published in final edited form as: Vasc Med. 2012 Jun 27;17(4):223–230. doi: 10.1177/1358863X12446213

Table 1.

Definitions of classification systems used to define collateral vessel number and size

Category	Number of collaterals^a
Category 1	0–3 collateral vessels
Category 2	4–7 collateral vessels
Category 3	≥ 8 collateral vessels
Collateral vessel grade	Size of collateral vessels
Grade 1	≤ 5 small
Grade 2	> 5 small
Grade 3	≤ 5 large ± small
Grade 4	> 5 large ± small

Small collaterals occupy < 25% of the length of the imaged thigh and < 50% of the diameter of the superficial femoral artery.¹⁹ Large collaterals occupy > 25% of the length of the imaged thigh and ≥ 50% of the diameter of the superficial femoral artery.¹⁹