Diabetic foot infection
Diabetic foot infection is a skin, soft tissue, or bone infection arising in an ulcer on a neuropathic, vasculopathic diabetic foot, diagnosed when pus or two or more inflammatory signs are present. Severity dictates therapy: mild infection is treated with oral dicloxacillin or cephalexin, while severe infection needs intravenous piperacillin-tazobactam plus vancomycin and urgent surgical debridement.
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What this article covers
- Overview
What it is: A skin, soft-tissue, or bone infection in a foot ulcer in a person with diabetes mellitus, ranging from cellulitis to abscess or osteomyelitis.
- Epidemiology
Typical patient: Long-standing diabetes mellitus with distal symmetric polyneuropathy, often peripheral arterial disease, who develops an ulcer on the plantar forefoot or heel after unrecognized trauma.
- Risk factors
Peripheral neuropathy: Loss of protective sensation is the dominant factor, since patients do not feel the trauma that starts the ulcer.
- Pathophysiology
The nerve lesion: Hyperglycemia damages peripheral nerve fibers, producing sensory loss, motor weakness that alters foot biomechanics, and autonomic denervation that dries and cracks the skin.
- Clinical features
The wound: A neuropathic ulcer is typically painless, punched-out, and surrounded by callus over a pressure point; an ischemic component adds pallor, coolness, and rest pain.
- Differential diagnosis
Acute Charcot neuroarthropathy: A hot, swollen foot resembles infection, but there is no ulcer, no purulence, and markers are often normal.
- Diagnosis
What establishes the diagnosis: Diagnosed clinically when a foot wound in a person with diabetes expresses pus, or when at least two of warmth, induration, erythema, pain, and tenderness are present…
- Management
First, classify severity and assess perfusion: debride overlying callus, grade the wound mild, moderate, or severe, and evaluate arterial supply, since critical ischemia raises antibiotic urgency.
- Complications
Osteomyelitis: Contiguous spread from a nonhealing ulcer to bone is the single most consequential complication, changing antibiotic duration and the likelihood of bone resection.
- Prognosis
Mortality: Diabetic foot infection, and osteomyelitis particularly, carries increased mortality versus diabetes without foot infection.
- Prevention
Structured foot screening: Comprehensive foot exam at diagnosis of type 2 diabetes and at least annually thereafter, with skin inspection, deformity assessment, pulse exam, and neurologic testing…
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Related articles
- Cellulitis
Cellulitis is a nonpurulent, spreading infection of the deep dermis and subcutaneous fat, usually caused by beta-hemolytic streptococci, diagnosed clinically and treated with antibiotics alone since there is no collection to drain.
- Osteomyelitis
Osteomyelitis is bone infection from hematogenous seeding or contiguous spread, most often from Staphylococcus aureus, presenting as subacute pain with or without a draining sinus tract and confirmed by bone biopsy culture. Empiric antibiotics are withheld until biopsy in a stable patient, and treatment combines source control with 4 to 6 weeks of culture-directed antibiotics, extended to 6 weeks or indefinite suppression for hardware-associated or chronic disease.
- Diabetic neuropathy
Diabetic neuropathy is length-dependent nerve damage from chronic hyperglycemia, most often a distal symmetric sensorimotor polyneuropathy causing numbness, pain, and loss of ankle reflexes, with autonomic, mononeuropathy, and radiculoplexus variants. Diagnosis is clinical after excluding other causes; management is tight glycemic control plus gabapentinoid or duloxetine therapy for painful symptoms.
- Type 2 diabetes mellitus
Type 2 diabetes is hyperglycemia from insulin resistance with progressive relative insulin deficiency, diagnosed by a hemoglobin A1c of 6.5% or higher, a fasting glucose of 126 mg/dL or higher, or a 2-hour oral glucose tolerance test value of 200 mg/dL or higher. First-line treatment is lifestyle modification plus metformin, with an SGLT2 inhibitor or GLP-1 receptor agonist added early for patients with atherosclerotic disease, kidney disease, or heart failure.
- Diabetic kidney disease
Diabetic kidney disease is the leading cause of chronic kidney disease and end-stage kidney disease worldwide, driven by chronic hyperglycemia acting through advanced glycation end products on the glomerulus. It is diagnosed clinically from progressive albuminuria and falling eGFR in a patient with long-standing diabetes and other microvascular disease, and treatment centers on RAS blockade, SGLT2 inhibition, and glycemic and blood pressure control.
- Necrotizing fasciitis
Necrotizing fasciitis is a rapidly progressive, life-threatening infection of the subcutaneous tissue and superficial fascia driven by vessel thrombosis and bacterial exotoxin production. The hallmark is pain out of proportion to visible skin findings, with crepitus, bullae, and woody induration in advanced disease. Diagnosis is confirmed by direct surgical exploration; the LRINEC score aids risk stratification. Treatment is emergent surgical debridement combined with broad-spectrum empiric antibiotics.