Inpatient / Infectious Disease
Diabetic Foot Wound
Admission Checklist
-- ABCs: evaluate for sepsis or shock
-- Triage: ensure adequate perfusion and does not need urgent vascular surgery; PEDIS Score
-- Chart Check: h/o diabetes (last A1c) and complications (neuropathy, retinopathy, nephropathy), peripheral vascular disease (PVD), renal function, prior ulcers, I+D, amputations, wound cultures, antibiotic allergies
-- Can’t Miss: necrotizing fasciitis (rapid spread or gas), gas gangrene (deep), osteomyelitis, ischemia (pain, pallor, pulseless, paresthesia, paralysis, poikilothermia)
-- Admission Orders: imaging with XRay and/or MRI, culture if purulent, consult to podiatry and vascular surgery
-- Initial Treatment to Consider: IV abx, glucose control, pain management
HPI Intake
-- Ulcer - duration, location, size, purulence
-- Local Symptoms: pain, swelling, numbness, tingling, burning
-- Systemic Symptoms: fever, chills, fatigue, weight loss
-- Prior Ulcers - prior hospitalizations, surgeries, amputation
-- Diabetes - current regimen, adherence, fills, checking sugars at home?
-- Foot Care - checks for cuts/blisters; ask about use of footwear or insoles
-- Smoking Status - current, former, how much
To Note on Exam
-- General - obesity, toxic appearance, distress
-- Extremities - edema, pulses (dorsal and pedal), dopplers, cap refill, skin temp, pallor, vibratory sensation, numbness (monofilament)
-- Skin - ulcer size, depth, erythema, drainage, odor, crepitus, bone/tender visible
Etiology/Differential
-- Vascular - venous stasis ulcer, arterial ulcer, lymphedema, thromboangiitis obliterans
-- Neuropathic - neuropathic ulcer, pressure ulcer
-- Infectious - bacterial (staph, strep, PsA, anaerobes), fungal
-- Autoimmune - pyoderma gangrenosum, vasculitis, Martorell ulcer
-- Other - malignant ulcer (SCC, melanoma), traumatic ulcer, chemical burn
EHR Dotphrase
Assessment
-- History: T2DM (A1c), CKD, prior foot infections, prior surgeries
-- Clinical: ulcer location, size, purulence, local and systemic symptoms
-- Exam: ulcer location, size, concern osteo
-- Data: WBC, ESR/CRP, A1c, Xray, MRI
-- DDx: venous stasis ulcer, arterial ulcer, lymphedema, pyoderma gangrenosum
Plan
Workup
-- Labs: CBC, ESR/CRP, A1c
-- Cultures: BCx if systemic illness or osteo/nec fasc; wound cultures from any procedure
-- Imaging: Xray of joint; MRI if c/f osteomyelitis
-- Bilateral ABIs if planning for a procedure or concern for PAD
-- Consults: podiatry for debridement, vascular surgery for possible revascularization
Treatment
-- Antibiotics: empiric at first, then narrow based on surgical cultures
- Mild - cephalexin, amox-clav, Bactrim, doxy for 1-2 weeks
- Mod/Severe - ceftriaxone + flagyl + vanc if concern for MRSA; pip-tazo if concern for pseudomonas
- Osteomyelitis - vanc and ceftriaxone/cefepime empirically, narrow based on bone biopsy cultures for a 6-week course
-- Debridement: all non-viable tissue; I+D or amputation as needed for infection or necrosis
-- Pain: acetaminophen, oxycodone for post-op pain; gabapentin for neuropathic pain; generally avoid ibuprofen in CKD
-- Pressure Offloading: casting/boot or knee-high walker
-- Glucose control: goal A1c <8% to promote healing; consider nutrition consult
-- Revascularization: discuss with podiatry and vascular surgery
-- Follow up with podiatry 2-4 weeks after surgery to assess healing
-- Regular foot inspections for the development of ulcers
If You Remember Nothing Else
Care for diabetic foot wounds requires a multidisciplinary team including podiatry, vascular surgery, and wound care. You can’t miss necrotizing fasciitis, gas gangrene, or osteomyelitis. Get a CT if you are concerned. Osteomyelitis should be diagnosed via MRI, and bone biopsies should guide antibiotic treatment. Treatment of diabetic foot wounds most commonly require strict glucose control, antibiotics, and debridement of dead tissue. Most infected ulcers are polymicrobial with mixed bacterial flora. Concurrent ischemia with poor blood flow drives poor outcomes and wound healing. Revascularization may be needed prior to procedures intended to salvage the limb. Pressure offloading is crucial after procedures to allow for healing. Patients should undergo regular foot inspection, especially if they have reduced sensation secondary to neuropath.
Clinical Pearls
Epidemiology and General Information
- Diabetic foot ulcers lead to over 1 million amputations annually
- Diabetic foot ulcers affect 15-25% of patients with diabetes over their lifetime
- 50% of patients with diabetic foot ulcers have PAD which impairs wound healing and increases amputation risk
- More than 50% of diabetic ulcers become infected
- 20% of diabetic foot infections lead to some type of amputation
- Five-year mortality after amputation for a diabetic foot ulcer is >70%
Pathophysiology
- Loss of protective sensation from peripheral neuropathy leads to repetitive and unnoticed traumas
- Motor neuropathy leads to abnormal walking and pressure points
- Ischemia from PAD impairs wound healing
- Callus formation leads to eventual subcutaneous hemorrhage and then the formation of an ulcer
- Hyperglycemia leads to the formation of advanced glycation end-products (AGEs), which impair collagen formation, prevent migration of inflammatory cells to wounds, and cause microvascular damage
Etiology and Risk Factors
- Prior foot ulcers are the greatest risk for recurrence (58% recurrence at 3 years, 65% at 5 years)
- The most important risk factors for the development of foot ulcers include poor glucose control, peripheral arterial disease (PAD), neuropathy, renal disease, smoking, callus, edema
Clinical Presentation and Diagnosis
- The plantar surface of the metatarsal head is the most common location. Other common locations include toes and heels. These are the common pressure points and sites of repetitive trauma.
- Osteomyelitis should be suspected if there is exposure of bone/tendon
- If you can probe to the bone on the exam, it is osteomyelitis by definition (LR 6.4)
- MRI is 90% sens, 82% spec for osteomyelitis, with high NPV (LR 0.14 if normal)
- Xrays can detect gas and the presence of bone changes; MRI is most sensitive for osteomyelitis
- ABIs are useful for PAD screening - considered severe if ABI is less than 0.4
- Erythrocyte sedimentation rate (ESR) is a non-specific inflammatory marker that measures the rate at which RBCs sediment in blood (in mm/hr) which reflects that levels of plasma proteins like fibrinogen and immunoglobulins which increase inflammation - it rises and falls slower than CRP
- C-reactive protein (CRP) is a more specific inflammatory marker for acute inflammation; it’s a protein produced in the liver in response to inflammation or infection and rises and falls quickly - the levels aren’t impacted by plasma components; it is more useful for monitoring response to treatment
- ESR >70 has an LR of 11 for osteomyelitis; useful for distinguishing between osteomyelitis and neuroarthropathy
- Persistently elevated ESR and CRP may indicate inadequate source control
Treatment
- Usually treat osteo with at least 6 weeks of antibiotics;
- If revascularization is not possible or unsuccessful and/or the tissue is necrotic or gangrenous and poses a risk to the patient’s life, amputation may be the only viable option for management
Trials and Literature
- IWGDF/IDSA Guidelines on Diagnosis and Treatment of Diabetes-Related Foot Infections (Diabetes Metab Res Rev, 2023)
- Diabetic Foot Ulcers and Their Recurrence: - Review (NEJM, 2017)
- Diabetic Foot Ulcers: A Review (JAMA, 2023)
- PO antibiotics with a fluoroquinolone and rifampin may be adequate to treat osteomyelitis (NEJM 2019)
Other Resources
- MD Calc - PEDIS Score - predicts 6-month risk of amputation and mortality in diabetic foot ulcers
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