Differentiation of chronic total occlusion and subtotal occlusion of the femoropopliteal artery—role of retrograde flow sign and collateral circulation on CT angiography images

OBJECTIVE: To study the value of a retrograde flow sign and the collateral circulation on CT angiography (CTA) for the differential diagnosis of chronic total occlusion from subtotal occlusion of the femoropopliteal artery (FPA). ABSTRACT: 50 patients with obstruction of the FPA underwent CTA and digital subtraction angiography examinations of the lower limbs. The frequency of a retrograde flow sign and collateral circulation on CTA in chronic total and subtotal occlusion was noted and analyzed, with the results of digital subtraction angiography as a standard to judge total or subtotal occlusion. The decreasing CT value from the distal to proximal direction on CTA suggests the existence of retrograde flow. RESULTS: There were significant differences in the occurrence rates of a retrograde flow sign on CTA in the chronic total and subtotal obstruction groups (X(2) = 13.1, p < 0.05), as well as a collateral circulation sign (X(2) = 13.5, p < 0.05). Employing both the retrograde flow sign and the collateral circulation sign to diagnose chronic total obstruction of the FPA had a sensitivity of 92.3% and specificity of 89.8%. CONCLUSION: The retrograde flow sign combined with a collateral circulation sign is of great clinical value for differentiation of chronic total stenosis from severe stenosis (subtotal occlusion) of the FPA. ADVANCES IN KNOWLEDGE: A retrograde flow sign combined with a collateral circulation sign is of great clinical value to differentiate between chronic total stenosis and severe stenosis (subtotal occlusion) of the FPA.