What is the likely cause of a reddish‑brown discoloration on the heel and how should it be evaluated and managed?

Reddish-Brown Discoloration of the Heel: Evaluation and Management

A reddish-brown discoloration on the heel most likely represents either a deep tissue injury (suspected deep tissue injury/DTI) or hemosiderin staining from chronic venous insufficiency, but in patients with diabetes or immobility, you must urgently rule out pressure-related deep tissue injury which carries high risk of progression to full-thickness necrosis.

Immediate Assessment Priority

The critical first step is determining if this represents pressure-related intact discolored areas of skin (PRIDAS), which can progress to severe tissue loss:

• Measure the temperature difference between the discolored area and adjacent normal skin using infrared thermometry or careful palpation 1
• Cool PRIDAS (temperature 1°C or more below adjacent skin) are 31.8 times more likely to progress to necrosis compared to warm PRIDAS 1
• Assess for capillary refill: the combination of nonblanching discoloration plus cool temperature predicts 65% progression to necrosis, while blanching with warm temperature shows 0% progression 1

Key Diagnostic Features to Evaluate

For Pressure-Related Deep Tissue Injury

• Patient risk factors: immobility, diabetes mellitus, previous pressure ulcers or scar tissue, suboptimal tissue perfusion 2
• The heel is anatomically vulnerable due to minimal subcutaneous tissue, no muscle or fascia, making it highly susceptible to pressure damage 2
• In diabetic patients with neuropathy and a red, hot, swollen foot, always consider active Charcot neuro-osteoarthropathy even if infection is present, as the IWGDF 2023 guidelines emphasize this diagnosis should not be excluded by concurrent infection 3

For Vascular Insufficiency

• Check for palpable pedal pulses, but note that their presence does not reliably rule out peripheral artery disease 3
• Measure toe pressures with toe-brachial index (TBI >0.7 makes PAD less likely; <30 mmHg predicts impaired healing) 3
• Ankle-brachial index may be falsely elevated due to medial artery calcification in diabetic patients with neuropathy 3

Diagnostic Imaging Algorithm

1. Plain radiographs first to exclude calcaneal fracture or bony pathology 3, 4
2. MRI is the gold standard if deep tissue injury or osteomyelitis is suspected, as it provides superior tissue characterization and can detect bone marrow edema 3, 4
3. Ultrasound can demonstrate fascial discontinuity if plantar fascia rupture is considered 4

Management Based on Etiology

If Pressure-Related Deep Tissue Injury (Cool, Nonblanching)

• Immediate complete offloading of the heel is mandatory 2
• Use heel protection devices and ensure the heel is suspended off all surfaces during bed rest 3
• Monitor closely for progression to full-thickness necrosis over 7-14 days 1
• Stage IV heel pressure ulcers (involving muscle, tendon, or bone) often require surgical intervention including debridement or partial calcanectomy 5

If Vascular Insufficiency Component

• Urgent vascular surgery consultation if toe pressure <30 mmHg or ankle pressure <50 mmHg 3
• Revascularization should be considered for wounds with signs of ischemia 3, 6
• A patent posterior tibial artery past the ankle predicts 86% healing success versus 57% without 6
• Normal renal function predicts 95% healing versus 55% with impaired function 6

If Diabetic Foot with Charcot Suspected

• MRI to confirm bone marrow edema without fractures (characteristic of stage 0 Charcot) 3
• Expert radiologist review is essential as bone marrow edema can mimic osteomyelitis 3
• Immobilization with total contact cast (TCC) or non-removable walker once infection controlled 3

Critical Pitfalls to Avoid

• Never dismiss a "red, hot, swollen foot" as infection alone in diabetic patients with neuropathy—always consider concurrent Charcot neuro-osteoarthropathy 3
• Do not rely solely on ankle-brachial index in diabetic patients due to medial artery calcification 3
• Avoid footbaths as they induce skin maceration 3
• Do not use chemical agents or plasters for self-removal of calluses 7

Wound Care Specifics

• Frequent wound inspection and debridement with scalpel 3
• Control exudate and maintain moist environment 3
• If infection present, obtain tissue specimens from debrided base (not superficial swabs) for culture 3
• Empiric antibiotics targeting S. aureus and streptococci for superficial infection; broad-spectrum for deep infection 3

Cardiovascular Risk Modification

In diabetic patients presenting with heel complications, this represents a critical opportunity for comprehensive risk reduction:

• Smoking cessation, cholesterol reduction, and hypertension treatment reduce major adverse cardiovascular and limb events 3
• SGLT-2 inhibitors should be considered once ulcer healed for cardiovascular and renal benefits 3
• Gradual glycemic control (avoid HbA1c drop >3% rapidly) to prevent treatment-induced neuropathy 3