Unless there are concomitant lesions in the aortoiliac or femoral/superficial femoral artery segments, the first manifestation of ischemia is frequently an ulcer or gangrene, rather than claudication. The gastrocnemius and soleus muscles may be supplied from collateral vessels from the popliteal artery; therefore, foot ischemia without attendant claudication may be the first sign of severe vascular insufficiency due to isolated tibial artery disease. The presence of ischemic rest pain or ulcers is termed chronic limb-threatening ischemia and is associated with the highest rate of amputation. Classically, ischemic rest pain is confined to the dorsum of the foot and is relieved with dependency: the pain does not occur with standing, sitting or dangling the leg over the edge of the bed. It is severe and burning in character, and because it is present only when recumbent, it may awaken the patient from sleep.
On examination, femoral and popliteal pulses may or may not be present depending on disease extent, but palpable pedal pulses will be absent. Dependent rubor may be prominent with pallor on elevation. The skin of the foot is generally cool, atrophic, and hairless.
B. Doppler and Vascular Findings
The ABI is often below 0.4; however, the ABI may be falsely elevated due to calcification of the arterial media layer (Mönckeberg medial calcific sclerosis) and may not be compressible. Toe-brachial indexes are preferred for assessing perfusion and predicting wound healing.
Digital subtraction angiography is the gold standard method to delineate the anatomy of the tibial-popliteal segment (eFigure 12–4). MRA or CTA is less helpful for detection of lesions in this location due to the small vasculature and other technical issues related to image resolution.
Magnetic resonance angiography of the arteries below the knee. Only the peroneal arteries are patent, which is the typical pattern in diabetic patients with atherosclerosis.