What is the cause of persistent foot edema in an 80-year-old diabetic patient 2 weeks after discontinuing paracetamol and ibuprofen, with normal liver and kidney function tests?

Causes of Persistent Foot Edema in an Elderly Diabetic Patient After Discontinuing Medications

The persistent foot edema in this 80-year-old diabetic patient is most likely due to diabetic peripheral neuropathy with possible Charcot neuroarthropathy, rather than medication-related effects, since the edema has continued for 2 weeks after discontinuation of paracetamol and ibuprofen.

Primary Causes to Consider

1. Diabetes-Related Causes

• Diabetic peripheral neuropathy: The most common cause of foot problems in elderly diabetic patients 1
• Charcot neuroarthropathy: A serious complication characterized by foot deformity, inflammation, and edema that persists even after resolution of infection 1
• Venous insufficiency: Common in diabetic patients and can lead to persistent edema 1

2. Medication-Related Causes (Less Likely in This Case)

• NSAID-induced edema: Ibuprofen can cause fluid retention and edema, but typically resolves within days after discontinuation 2, 3
• Peripheral edema from NSAIDs: Usually resolves within 72 hours after discontinuation 4

Diagnostic Approach

1. Assess for neuropathy:

   • Test for loss of protective sensation using 10g Semmes-Weinstein monofilament 1
   • Check vibration perception with 128-Hz tuning fork 1
   • Evaluate for symptoms like tingling, pain, or numbness 5

2. Examine for foot deformities:

   • Look for flattened midfoot, prominent metatarsal heads, or other structural abnormalities 1
   • Assess for limited joint mobility 1

3. Evaluate vascular status:

   • Check pedal pulses 1
   • Consider ankle-brachial index (ABI) if pulses are diminished 1
   • Look for signs of venous insufficiency 1

4. Rule out infection:

   • Check for erythema, warmth, tenderness, or purulent discharge 1
   • Evaluate for systemic signs of infection (fever, elevated white blood cell count) 1

5. Consider imaging:

   • X-ray to evaluate for foot deformities or Charcot changes 1
   • MRI may be necessary if Charcot neuroarthropathy is suspected 1

Management Recommendations

1. For diabetic neuropathy with edema:

   • Elevate legs regularly 6
   • Prescribe properly fitting therapeutic footwear with demonstrated pressure-relieving effect 1
   • Consider compression stockings if venous insufficiency is present 6

2. For suspected Charcot neuroarthropathy:

   • Immediate offloading with total contact cast or removable walker boot 1
   • Referral to a multidisciplinary diabetic foot care team 1
   • Regular monitoring every 1-3 months 1

3. Patient education:

   • Daily foot inspection 1
   • Proper foot hygiene including daily washing with careful drying between toes 1
   • Avoidance of barefoot walking 1
   • Monitoring for pre-ulcerative signs 1

Important Considerations

1. Risk stratification: This patient falls into IWGDF risk category 2 or 3 (peripheral neuropathy with foot deformity) requiring follow-up every 1-3 months 1

2. Multidisciplinary care: Involvement of specialists including endocrinology, podiatry, and vascular surgery is crucial for optimal management 1

3. Pitfalls to avoid:

   • Don't attribute persistent edema solely to medication effects when it continues beyond 2 weeks after discontinuation
   • Don't overlook Charcot neuroarthropathy, which can be misdiagnosed as infection or simple edema
   • Don't delay offloading if Charcot is suspected, as this can lead to permanent deformity 1

The persistent foot edema in this elderly diabetic patient requires thorough evaluation for diabetic foot complications, particularly neuropathy and Charcot neuroarthropathy, rather than continued focus on medication-related causes, since the edema has persisted well beyond the expected resolution time for medication effects.