Health Dictionary

Synonyms and keywords: Diabetic feet; Diabetic ulcer; Diabetic foot infection; Diabetic foot ulcer

Overview

Diabetic foot is a complication of long-standing and poorly controlled diabetes mellitus. Poor glycemic control, peripheral neuropathy, improper footwear, ischemia and possible foot deformities including charcot arthropathy are the main known causes of diabetic foot. A detailed history of the patient‘s diabetes status, foot care, deformities, foot hygiene, symptoms of ischemia, and history of smoking is necessary to classify the wound or ulcer and treat the underlying cause. Physical examination includes an assessment of the ulcer and tests to detect the severity of peripheral neuropathy (such as Semmes-Weinstein monofilament test) and ischemia (such as Ankle-Brachial Index (ABI)). Routine laboratory investigations are recommended, such as HbA1c. If an infection is suspected, a wound culture is necessary to guide antibiotic therapy. Mechanical offloading such as cast walkers, total contact casting or therapeutic shoes, and podiatric care are essential. Surgical interventions, such as revascularization surgery) may be considered for patient’s with ischemia. Antibiotic therapy is based on culture, risk of MRSA infection, risk of pseudomonas infection, presence or absence of complications, such as osteomyelitis and history of recent antibiotic use. Hyperbaric oxygen therapy is considered for a diabetic foot that persists despite treatment for more than 30 days.

Causes

Life Threatening Causes

Life-threatening causes include conditions that may result in death or permanent disability within 24 hours if left untreated. Diabetic foot superseded with the following may result in sepsis and death.^[1]

Common Causes

Poor glycemic control
Peripheral neuropathy
- Autonomic neuropathy
- Somatic/Motor neuropathy
Peripheral arterial disease
Peripheral ischemia
Improper footwear
Foot deformities including charcot arthropathy

Diagnosis

Assessment of diabetic foot includes evaluation of peripheral arterial disease, peripheral neuropathy, and foot deformities. Shown below is an algorithm summarizing the diagnosis of diabetic foot and diabetic foot ulcers according to the recommendations of the American Diabetes Association and International Diabetes Federation- Clinical Practice Recommendations on the Diabetic Foot 2017. ^[3]^[1]

Characterize the symptoms:
❑ Onset
❑ Type of sensation
❑ Location
❑ Nocturnal variation
❑ Aggravating factors
❑ Relieving factors

Obtain a detailed history:
❑ Onset of diabetes
❑ Duration of diabetes
❑ Compliance with medication
❑ History of glycemic control
❑ History of other diabetic complications
❑ Foot deformities/injuries/ulcers
❑ History of lower limb amputation
❑ Type of footwear
❑ Foot hygiene
❑ History of claudication
❑ Smoking history

Examine the patient:
Inspection
❑ Location of ulcer
❑ Integrity and charcteristic (dry/cracked) of skin
❑ Sweating
Palpation
❑ Pedal (dorsalis pedis) pulses
❑ Vibration sensation
❑ Ulcer site- warmth, tenderness, edema
Non-invasive tests
❑ Semmes-Weinstein monofilament test
❑ Probe-to-bone test if suspected osteomyelitis
❑ Measure ABI (Ankle-Brachial Index) with a Arterial doppler

Order tests:
❑ Glycosylated hemoglobin/ HbA1c
❑ Fasting plasma glucose
❑ Complete blood count
❑ ESR and CRP
❑ Deep tissue specimen for culture

Treatment

Assessment of diabetic foot includes evaluation of peripheral arterial disease, peripheral neuropathy, and foot deformities. Shown below is an algorithm summarizing the diagnosis of diabetic foot and diabetic foot ulcers according to the recommendations of the American Diabetes Association and International Diabetes Federation- Clinical Practice Recommendations on the Diabetic Foot 2017. ^[4] ^[5] ^[6] ^[1]

Adapted from Diabetes Care. 2013;36(9):2862-71. and Clin Infect Dis. 2012;54(12):e132-73. ^[7] ^[8]

Prophylactic measures and Diabetic foot care in all patients
❑ Glycemic control
❑ Apporpriate footwear and podiatric care
• ❑ Mechanical offloading
• Cast Walkers
• Total contact casting
• Therapeutic shoes
❑ Vascular care to prevent and treat peripheral arterial disease

❑ Local wound care
❑ Debridement – Mechanical or chemical

Peripheral arterial disease or signs of ischemia

Medication/Surgical or endovascular revascularization

Presence of infection

• Mechanical or chemical wound debridement
• Culture • Biopsy

• Assess severity of infection according to the table below
• Treat with antiobiotics according to the table below

If infection does not resolve within 30 days-
• Consider hyperbaric oxygen therapy

• Observe foot
• Establish regular care
• Reassess in 2-3 months

DFI is classified based on its severity according to the Infectious Diseases Society of America (IDSA) guideline or the PEDIS grade developed by the International Working Group on the Diabetic Foot (IWGDF). (see Table below)
Selection of an empiric antimicrobial regimen should be determined by the severity of DFI and the likely etiologic agents.

Clinical Manifestation	PEDIS Grade	IDSA Severity
Wound lacking purulence or any manifestations of inflammation	1	Uninfected
Presence of ≥2 manifestations of inflammation (purulence, or erythema, pain, tenderness, warmth, or induration) Any cellulitis or erythema extends ≤2 cm around the ulcer Limited to the skin or superficial subcutaneous tissues No other local complications (eg, trauma, gout, acute Charcot neuro-osteoarthropathy, fracture, thrombosis, venous stasis) or systemic illness	2	Mild
Infection in a patient who is metabolically stable and systemically well, but with ≥1 of the following characterisitics: Cellulitis extending >2 cm Lymphangitic streaking Spread beneath the superficial fascia Deep-tissue abscess Gangrene Involvement of muscle, tendon, joint, or bone	3	Moderate
Infection in a patient with metabolic instability (eg, acidosis, severe hyperglycemia, or azotemia) or systemic toxicity as manifested by ≥2 of the following: Temperature >38 °C or <36 °C Heart rate >90 beats/min Respiratory rate >20 breaths/min or PaCO2 <32 mm Hg White blood cell count >12,000 or <4,000 cells/μL or ≥10% immature (band) forms	4	Severe

5. What is the appropriate route, setting, and duration of antibiotic therapy?

The table below describes the recommended route, setting, and duration of antibiotic therapy based on the extent and severity of DFI.

Site of Infection, by Severity or Extent		Route of Administration	Setting	Duration of Therapy
Soft-tissue only	Mild (Grade 2)	Oral (or topical for superficial infections)	Outpatient	1–2 wk
	Moderate (Grade 3)	Oral (or initial parenteral)	Outpatient (or inpatient)	1–3 wk
	Severe (Grade 4)	Initial parenteral, switch to oral when possible	Inpatient, then outpatient	2–4 wk
Bone or joint	No residual infected tissue	Parenteral or oral	Inpatient, then outpatient	2–5 d
	Residual infected soft tissue	Parenteral or oral	Inpatient, then outpatient	1–3 wk
	Residual infected, viable bone	Initial parenteral, switch to oral when possible	Inpatient, then outpatient	4–6 wk
	Residual dead bone or no surgery	Initial parenteral, switch to oral when possible	Inpatient, then outpatient	≥3 mo

Empiric Therapy

▸ Click on the following categories to expand treatment regimens.

Uninfected (Grade 1)

▸ No Evidence of Infection

Mild (Grade 2)

▸ Acute Infection Without Recent Antibiotic Use

▸ High Risk for MRSA

Moderate to Severe (Grade 3–4)

▸ Chronic Infection or Recent Antibiotic Use

▸ High Risk for MRSA

▸ High Risk for Pseudomonas aureuginosa

▸ Polymicrobial Infection

Uninfected Wound, No Evidence of Infection
▸ Uninfected wounds should be managed with appropriate wound care. ▸ Antibiotic therapy is not recommended.

Mild DFI, Acute Infection Without Recent Antibiotic Use
Preferred Regimen
▸ Dicloxacillin 125–250 mg PO qid OR ▸ Clindamycin 150–300 mg PO qid ^† OR ▸ Cephalexin 500 mg PO qid OR ▸ Levofloxacin 750 mg PO qd OR ▸ Amoxicillin-Clavulanate 500 mg PO bid (or 250 mg PO tid) ^‡
^† Usually active against community-associated MRSA, but check macrolide sensitivity and consider ordering a D-test before using for MRSA. ^‡ Relatively broad-spectrum oral agent that includes anaerobic coverage.

Mild DFI, High Risk for MRSA
Preferred Regimen
▸ Doxycycline 100 mg PO q12h ^† OR ▸ TMP–SMX 80-160 mg/400-800 mg PO q12h ^†
^† Active against many MRSA & some gram-negatives; uncertain against streptococci.

Moderate to Severe DFI, Chronic Infection or Recent Antibiotic Use
Preferred Regimen
▸ Levofloxacin 750 mg IV/PO q24h OR ▸ Cefoxitin 1 g IV q4h (or 2 g IV q6–8h) OR ▸ Ceftriaxone 1–2 g/day IV/IM q12–24h OR ▸ Ampicillin–Sulbactam 1.5–3 g IV/IM q6h OR ▸ Moxifloxacin 400 mg IV/PO q24h OR ▸ Ertapenem 1 g IV/IM q24h OR ▸ Tigecycline 100 mg IV, then 50 mg IV q12h ^† OR ▸ Imipenem–Cilastatin 0.5–1 g IV q6–8h ^‡
Alternative Regimen
▸ Levofloxacin 750 mg IV/PO q24h OR ▸ Ciprofloxacin 600–1200 mg/day IV q6–12h OR ▸ Ciprofloxacin 1200–2700 mg IV q6–12h (for more severe cases)
PLUS
▸ Clindamycin 150–300 mg PO qid
^† Active against MRSA. ^‡ Not active against MRSA; consider when ESBL-producing pathogens suspected.

Moderate to Severe DFI, High Risk for MRSA
Preferred Regimen
▸ Linezolid 600 mg IV/PO q12h OR ▸ Daptomycin 4 mg/kg IV q24h OR ▸ Vancomycin 15–20 mg/kg IV q8–12h (trough: 10–20 mg/L)

Moderate to Severe DFI, High Risk for Pseudomonas aeruginosa
Preferred Regimen
▸ Piperacillin–Tazobactam 3.375 g IV q6–8h

Moderate to Severe DFI, Polymicrobial Infection
Preferred Regimen
▸ Vancomycin 15–20 mg/kg IV q8–12h (trough: 10–20 mg/L) OR ▸ Linezolid 600 mg IV/PO q12h OR ▸ Daptomycin 4 mg/kg IV q24h
PLUS
▸ Piperacillin–Tazobactam 3.375 g IV q6–8h OR ▸ Imipenem–Cilastatin 0.5–1 g IV q6–8h OR ▸ Ertapenem 1 g IV/IM q24h OR ▸ Meropenem 1 g IV q8h
Alternative Regimen
▸ Vancomycin 15–20 mg/kg IV q8–12h (trough: 10–20 mg/L) OR ▸ Linezolid 600 mg IV/PO q12h OR ▸ Daptomycin 4 mg/kg IV q24h
PLUS
▸ Ceftazidime 2 g IV q8h OR ▸ Cefepime 2 g IV q8h OR ▸ Aztreonam 2 g IV q6–8h
PLUS
▸ Metronidazole 15 mg/kg IV, then 7.5 mg/kg IV q6h

Do’s

Check for signs of ischemia.
Check for signs of infection.
Always get a wound culture to determine the type of organism and choice of an antibiotic.
Prophylactic podiatric care.
Mechanical offloading in all patients. ^[5]

Don’ts

Don’t treat the ulcer without treating the underlying infection, ischemia, and appropriate glycemic control.

References

↑ ^1.0 ^1.1 ^1.2 ^1.3 Pendsey SP (2010). “Understanding diabetic foot”. Int J Diabetes Dev Ctries. 30 (2): 75–9. doi:10.4103/0973-3930.62596. PMC 2878694. PMID 20535310.
↑ Hobizal KB, Wukich DK (2012). “Diabetic foot infections: current concept review”. Diabet Foot Ankle. 3. doi:10.3402/dfa.v3i0.18409. PMC 3349147. PMID 22577496.
↑ “Guidelines”.
↑ “Guidelines”.
↑ ^5.0 ^5.1 American Diabetes Association (2020). “11. Microvascular Complications and Foot Care: Standards of Medical Care in Diabetes-2020”. Diabetes Care. 43 (Suppl 1): S135–S151. doi:10.2337/dc20-S011. PMID 31862754.
↑ Rathur HM, Boulton AJ (2007). “The diabetic foot”. Clin Dermatol. 25 (1): 109–20. doi:10.1016/j.clindermatol.2006.09.015. PMID 17276208.
↑ Lipsky BA, Berendt AR, Cornia PB, Pile JC, Peters EJ, Armstrong DG; et al. (2012). “2012 Infectious Diseases Society of America clinical practice guideline for the diagnosis and treatment of diabetic foot infections”. Clin Infect Dis. 54 (12): e132–73. doi:10.1093/cid/cis346. PMID 22619242.
↑ Wukich DK, Armstrong DG, Attinger CE, Boulton AJ, Burns PR, Frykberg RG; et al. (2013). “Inpatient management of diabetic foot disorders: a clinical guide”. Diabetes Care. 36 (9): 2862–71. doi:10.2337/dc12-2712. PMC 3747877. PMID 23970716.

[pmid20535310-1] 1.0 ^1.1 ^1.2 ^1.3 Pendsey SP (2010). “Understanding diabetic foot”. Int J Diabetes Dev Ctries. 30 (2): 75–9. doi:10.4103/0973-3930.62596. PMC 2878694. PMID 20535310.

[pmid22577496-2] Hobizal KB, Wukich DK (2012). “Diabetic foot infections: current concept review”. Diabet Foot Ankle. 3. doi:10.3402/dfa.v3i0.18409. PMC 3349147. PMID 22577496.

[3] “Guidelines”.

[4] “Guidelines”.

[pmid31862754-5] 5.0 ^5.1 American Diabetes Association (2020). “11. Microvascular Complications and Foot Care: Standards of Medical Care in Diabetes-2020”. Diabetes Care. 43 (Suppl 1): S135–S151. doi:10.2337/dc20-S011. PMID 31862754.

[pmid17276208-6] Rathur HM, Boulton AJ (2007). “The diabetic foot”. Clin Dermatol. 25 (1): 109–20. doi:10.1016/j.clindermatol.2006.09.015. PMID 17276208.

[pmid22619242-7] Lipsky BA, Berendt AR, Cornia PB, Pile JC, Peters EJ, Armstrong DG; et al. (2012). “2012 Infectious Diseases Society of America clinical practice guideline for the diagnosis and treatment of diabetic foot infections”. Clin Infect Dis. 54 (12): e132–73. doi:10.1093/cid/cis346. PMID 22619242.

[pmid23970716-8] Wukich DK, Armstrong DG, Attinger CE, Boulton AJ, Burns PR, Frykberg RG; et al. (2013). “Inpatient management of diabetic foot disorders: a clinical guide”. Diabetes Care. 36 (9): 2862–71. doi:10.2337/dc12-2712. PMC 3747877. PMID 23970716.

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