Diabetic Leg Discoloration: Diagnostic Considerations and Management

Primary Diagnostic Considerations

The American Heart Association suggests that peripheral arterial disease (PAD) is the leading diagnosis to exclude in any diabetic patient presenting with leg discoloration, as it occurs 2-4 times more frequently in diabetics than the general population and progresses more rapidly 3.
The European Society of Cardiology recommends that key clinical features of PAD-related discoloration include dependent rubor (reddish-purple discoloration when leg is dependent) and pallor on elevation (leg becomes pale when raised above heart level) 2, 4.
The American Diabetes Association notes that absence of hair growth on the affected limb and dystrophic toenails are also indicative of PAD 2, 3.
Skin temperature changes (cool to touch in ischemia) are an important diagnostic feature of PAD, according to the American Diabetes Association 5.

The European Society of Cardiology recommends performing a vascular assessment, including palpation of femoral, popliteal, dorsalis pedis, and posterior tibial pulses bilaterally, and assessing skin temperature and color changes 1, 5.
The American Diabetes Association suggests performing a neurological assessment, including 10-g monofilament testing at multiple plantar sites and testing for loss of protective sensation (present in most diabetic foot complications) 5, 6.

The American Heart Association recommends that Ankle-Brachial Index (ABI) measurement is mandatory as the first objective test, even if pulses are palpable, since clinical examination alone is unreliable in diabetes 8, 3.
The European Society of Cardiology notes that ABI interpretation is as follows: ABI <0.9 is diagnostic of PAD, ABI <0.6 indicates significant ischemia affecting wound healing potential, and ABI <0.5 or ankle pressure <50 mmHg indicates severely impaired circulation, critical limb ischemia 1, 2, 3.

The American Diabetes Association warns that assuming normal perfusion based on palpable pulses alone is a dangerous error, as up to 50% of diabetic foot ulcer patients have PAD despite seemingly adequate examination findings 1.
The European Society of Cardiology notes that medial arterial calcification (common in diabetes) falsely elevates ABI readings, potentially missing critical ischemia, and recommends using toe pressures or TcPO2 when ABI >1.3 2, 3, 8, 5.

The American Heart Association recommends urgent referral to vascular surgery if PAD is confirmed with ABI <0.5, ankle pressure <50 mmHg, toe pressure <30 mmHg, or TcPO2 <25 mmHg, and revascularization should be attempted before considering amputation 8, 5, 1.
The American Diabetes Association suggests that multidisciplinary diabetic foot team involvement is essential in the management of diabetic foot complications 1, 5.