What are the bubble indentations on the heel of a foot, possibly indicating fat pad atrophy or pressure ulcer, especially in a patient with a history of immobility or poor circulation?

Bubble Indentations on the Heel

Bubble indentations on the heel most likely represent pitting edema from fluid accumulation, which requires immediate assessment for deep venous thrombosis (DVT), heart failure, or peripheral vascular disease, especially if unilateral or accompanied by other concerning signs.

Immediate Clinical Assessment Required

Pitting edema is the most common cause of bubble-like indentations on the heel, occurring when pressure applied to swollen tissue leaves a temporary depression or "bubble" mark 1. This finding demands urgent evaluation because:

• Unilateral leg swelling with pitting edema confined to one leg scores points on the Wells DVT criteria and may indicate acute DVT, particularly if the patient has recent immobility, surgery within 12 weeks, or other risk factors 1
• Bilateral pitting edema in the feet, ankles, or lower extremities is a cardinal sign of heart failure and requires assessment for other HF symptoms including dyspnea, fatigue, or reduced exercise tolerance 2
• In diabetic patients, any heel abnormality including edema warrants immediate vascular assessment because up to 50% of diabetic foot complications involve coexisting peripheral artery disease (PAD) 3

Differential Diagnosis Algorithm

First: Rule Out DVT (if unilateral)

• Calculate Wells score immediately: entire leg swelling (+1 point), pitting edema confined to symptomatic leg (+1 point), recent major surgery (+1 point) 1
• If Wells score ≥3, proceed directly to complete duplex ultrasound without waiting for D-dimer, as DVT is likely and requires immediate anticoagulation 1
• Bilateral common femoral vein spectral Doppler waveforms should be obtained 1

Second: Assess for Heart Failure (if bilateral)

• Look for at least 2 physical examination findings: peripheral edema with pitting indentation in feet/ankles/legs, increased jugular venous pressure, pulmonary rales, S3 gallop, or rapid weight gain (>3-4 lbs in 3-4 days) 2
• Peripheral edema with pitting indentation when pressed is one of the required physical examination findings for diagnosing new or worsening heart failure 2

Third: Evaluate Vascular Status (especially in diabetic or immobile patients)

• Absent or diminished pedal pulses require immediate objective vascular assessment with ankle-brachial index (ABI), toe-brachial index (TBI), and pedal Doppler waveforms, as palpable pulses alone cannot exclude significant PAD 3
• Cool lower limb temperature compared to the contralateral side indicates PAD 3
• Prolonged venous filling time (>20 seconds) predicts poor healing 3

Alternative Diagnoses to Consider

Pressure Ulcer with Surrounding Edema

• The heel is highly vulnerable to pressure damage because it has no muscle or fascia and little subcutaneous tissue 4
• Immobility, previous pressure ulcers, scar tissue, and suboptimal tissue perfusion increase vulnerability 4
• 10-20% of heel pressure ulcers involve deeper tissues (stage IV) including muscle, tendon, or bone 5
• Pressure ulcers are typically polymicrobial when infected, involving both aerobes (S. aureus, Enterococcus, Proteus, E. coli, Pseudomonas) and anaerobes (Peptococcus, Bacteroides fragilis, Clostridium perfringens) 2

Heel Fat Pad Pathology

• The heel fat pad is specialized adipose tissue that provides cushioning and overlies the inferior and posterior calcaneus 6
• Inflammatory-edematous patterns of heel fat pad involvement occur in 6.6% of rheumatoid arthritis patients and cause subcalcaneal pain 7
• Degenerative-atrophic changes (1.1-1.9% prevalence) are associated with plantar fasciitis and subcalcaneal enthesophytes 7
• Heel fat pad lesions are rare but can cause debilitating heel pain 6

Critical Actions and Common Pitfalls

Do Not Delay Vascular Assessment

• Never assume PAD is absent based solely on palpable pulses—even skilled examiners can detect pulses despite significant ischemia 3
• Never rely on ABI alone in diabetic patients, as arterial calcification causes falsely elevated readings (≥1.3); always obtain TBI or waveform analysis 3
• Clinical examination sensitivity is too low to rule out PAD; objective testing is mandatory in all heel abnormalities 3

Immediate Imaging Indications

• Consider urgent vascular imaging and revascularization if ankle pressure <50 mmHg or ABI <0.5 2
• Toe pressure <30 mmHg or transcutaneous oxygen pressure (TcPO2) <25 mmHg requires urgent vascular imaging 2
• Proceed to complete duplex ultrasound for suspected DVT rather than limited protocols, as limited studies require repeat imaging in 5-7 days and delay treatment 1

High-Risk Patient Populations

• Diabetic patients require complete annual foot examination including skin integrity evaluation, 10g monofilament testing, pulse examination, and deformity assessment 8
• High-risk diabetic patients (IWGDF risk 2-3) need evaluation every 1-3 months 2, 8
• All bed-bound patients require daily self-examination of sacral, ischial, trochanteric, and heel areas for pressure ulcer development 9