This study aims to evaluate the accuracy of Duplex Ultrasound (DUS) in assessing infra inguinal arterial lesions in patients with chronic threatening limb ischemia compared with digital subtraction angiography (DSA) as the reference standard. By comparing sensitivity, specificity, and predictive values across arterial segments, the study seeks to determine the clinical utility of DUS as a non-invasive alternative for pre-intervention vascular mapping in chronic limb-threatening ischemia.

Inclusion Criteria:

- 1. Clinical diagnosis of chronic threatening lower limb ischemia (rest pain, non-healing ulcer, or gangrene).

2. Ability to provide informed consent.

Exclusion Criteria:

• 1. Hemodynamically unstable patients not fit for angiography. 2. Patients with non-atherosclerotic arterial diseases (e.g., vasculitis, Buerger's disease).

  3. Known contrast allergy or renal insufficiency precluding contrast angiography.

  4. Inadequate acoustic window or inability to undergo complete DUS examination.