← Back to Browse
Ask AleraHome
CT
Lower Extremity VasculatureDemonstration data

CTA Lower-Limb Runoff

CT angiography of the lower-limb runoff evaluates the arterial tree from the infrarenal aorta and iliac arteries through the femoropopliteal segment to the tibial and pedal vessels. It is a primary non-invasive tool for peripheral arterial disease, mapping stenoses, occlusions and runoff for revascularisation planning.

Indications

  • Intermittent claudication with an abnormal ankle-brachial index
  • Critical (chronic) limb-threatening ischaemia with rest pain or tissue loss
  • Pre-procedural planning for endovascular or surgical revascularisation
  • Acute limb ischaemia and suspected arterial embolism or thrombosis
  • Surveillance of bypass grafts, stents and known aneurysms

Contraindications & Cautions

  • Severe iodinated contrast allergy without adequate premedication
  • Significant renal impairment (balance diagnostic need against contrast nephrotoxicity)
  • Extensive vascular calcification limiting luminal assessment (consider alternative imaging)
  • Haemodynamic instability precluding transport and acquisition

Patient Preparation

  • Screen for iodinated contrast allergy and assess renal function
  • Secure reliable intravenous access, ideally antecubital, for power injection
  • Position the patient supine with the feet secured and immobilised
  • Warm the room and consider vasodilatation strategies to optimise distal opacification

Technique & Parameters

  • Bolus tracking with region of interest in the suprarenal/infrarenal aorta, or a test bolus, to time the acquisition
  • Coverage from the renal arteries or aortic bifurcation to the pedal arteries
  • Contrast 100-150 mL at 4-5 mL/s with a saline chaser; biphasic injection to prolong distal enhancement
  • Slow table speed or delayed acquisition to accommodate slow distal flow in severe disease
  • Thin collimation (≤1 mm) with MIP, curved planar and volume-rendered reformats for reporting

Systematic Review

  • Assess the infrarenal aorta and iliac arteries for stenosis, occlusion and aneurysm
  • Evaluate the common femoral, superficial femoral and profunda femoris arteries
  • Trace the popliteal artery and the tibioperoneal trunk
  • Count and grade the three-vessel tibial runoff (anterior tibial, posterior tibial, peroneal) to the pedal arch
  • Review collateral pathways, grafts, stents and any signs of dissection or embolism

Key Findings & Significance

  • Focal or long-segment stenoses and occlusions with quantifiable luminal narrowing
  • Superficial femoral artery occlusion at the adductor (Hunter) canal with reconstitution via collaterals
  • Distribution of atherosclerotic and medial (Monckeberg) calcification affecting luminal evaluation
  • Number of patent runoff vessels and integrity of the pedal arch (key for bypass planning)
  • Aneurysm (e.g. popliteal), in-stent restenosis, graft stenosis or thrombosis

Differential Considerations

  • Atherosclerotic peripheral arterial disease versus embolic occlusion
  • Popliteal artery entrapment syndrome versus cystic adventitial disease in younger patients
  • Thromboangiitis obliterans (Buerger disease) versus diffuse distal atherosclerosis
  • Vasculitis versus atherosclerotic stenosis
  • True luminal stenosis versus artefactual narrowing from dense calcification or blooming

Pearls & Pitfalls

  • Mistimed acquisition can outrun the contrast bolus distally, mimicking occlusion; verify enhancement to the feet
  • Heavy tibial calcification degrades luminal assessment; dual-energy or duplex ultrasound can complement CTA
  • Document the number of patent runoff vessels and pedal arch, as these determine bypass target and outcome
  • Correlate with ankle-brachial index and clinical stage (e.g. Rutherford classification) in the report

Structured Report

  • Report segment by segment from aorta to pedal arteries with location and severity of disease
  • Grade stenoses (e.g. <50%, 50-70%, 70-99%, occlusion) and give occlusion lengths
  • State the number and quality of tibial runoff vessels and pedal arch patency
  • Describe grafts, stents, aneurysms and any complications
  • Provide an integrated conclusion supporting endovascular versus surgical planning

References

  • ACR-NASCI-SPR Practice Parameter for the Performance and Interpretation of Body CT Angiography
  • Radiographics: Fleischmann D et al. CT Angiography of Peripheral Arterial Disease
  • ACR Appropriateness Criteria: Lower Extremity Arterial Claudication - Non-Invasive Vascular Imaging
  • ACC/AHA Guideline on the Management of Patients with Lower Extremity Peripheral Artery Disease

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.