Most Likely Diagnosis: Peripheral Arterial Disease (PAD)
The clinical presentation of numbness and burning pain in the right foot that occurs at rest (within 20 minutes of lying down), is relieved by dependency (hanging the leg over the bed), and is associated with dependent rubor (redness) is pathognomonic for peripheral arterial disease with critical limb ischemia, not diabetic peripheral neuropathy. 1, 2
Key Distinguishing Clinical Features
Why This is PAD, Not Diabetic Neuropathy
Pain timing: PAD causes rest pain that worsens when the leg is elevated (lying flat in bed) because gravity no longer assists blood flow to the ischemic foot 1, 3
Relief with dependency: Hanging the leg over the bed provides immediate relief because gravity improves arterial perfusion to the ischemic tissues—this is a classic sign of critical limb ischemia 1, 2
Dependent rubor: The foot becomes red when dependent due to maximal vasodilation in response to severe ischemia, which is a hallmark physical finding of advanced PAD 1, 2
Diabetic neuropathy characteristics differ: Neuropathic pain is typically worse at night but is not consistently relieved by positional changes, does not cause dependent rubor, and affects both feet symmetrically in a stocking-glove distribution 1, 2, 4
Immediate Diagnostic Steps Required
Vascular Assessment (Priority)
Palpate dorsalis pedis and posterior tibial pulses bilaterally—absence or diminishment strongly suggests PAD, present in up to 24% of diabetic patients aged 55-74 2
Assess for rubor on dependency and pallor on elevation—this Buerger's test confirms severe arterial insufficiency 1, 2
Check capillary refill time—prolonged refill (>3 seconds) indicates poor perfusion 2
Obtain ankle-brachial index (ABI) immediately—this is the definitive bedside test to confirm PAD, with ABI <0.9 diagnostic and <0.4 indicating critical limb ischemia 1, 2, 3
Critical Pitfall to Avoid
Do not assume this is diabetic neuropathy based solely on the patient's diabetes diagnosis. Up to 40% of patients with diabetic foot infections have concurrent PAD, and the presence of diabetes increases the likelihood of both conditions 1. However, the specific symptom pattern described—rest pain relieved by dependency with dependent rubor—is virtually diagnostic of PAD and requires urgent vascular evaluation 1, 2.
Urgent Management Implications
Why This Distinction Matters for Morbidity and Mortality
PAD with rest pain represents critical limb ischemia, which carries a high risk of limb loss without revascularization 1
Prompt referral to vascular surgery is mandatory when clinical or imaging evidence of significant ischemia is present in an infected or threatened limb 1
Treatment differs fundamentally: Neuropathy requires glycemic control and neuropathic pain medications 1, 2, while critical limb ischemia requires urgent revascularization to prevent amputation 1
Immediate Actions
Obtain ABI testing today—this simple bedside test with sphygmomanometers and handheld Doppler definitively establishes the diagnosis 1, 2
Refer urgently to vascular surgery if ABI <0.4 or if rest pain with dependent rubor is confirmed, as this indicates critical limb ischemia requiring revascularization 1
Assess for foot wounds or infection using the IDSA criteria (erythema, warmth, tenderness, purulent discharge), as PAD with infection requires interdisciplinary care and may necessitate emergent revascularization before debridement 1
Secondary Consideration: Coexistent Neuropathy
While PAD is the primary diagnosis explaining this symptom complex, diabetic neuropathy may coexist and complicate the clinical picture 1, 2. However, neuropathy alone does not cause positional pain relief or dependent rubor 2, 4. After addressing the vascular emergency, assess for neuropathy using 10-g monofilament testing, as loss of protective sensation increases ulceration risk 1, 4.