Differentiating Diabetic foot from other diseases

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Anahita Deylamsalehi, M.D.[2]

Overview

Diabetic foot must be differentiated from other diseases that cause foot ulceration, erythema, swelling and skin lesion, such as skin and soft-tissue infections, gas gangrene, cellulitis, deep venous thrombosis and inflammatory disorders.

Differentiating Diabetic foot from other Diseases

• Diabetic foot must be differentiated from other diseases that cause foot ulceration, erythema, swelling and skin lesion, such as:
  • Skin and soft-tissue infections:
    • Gas gangrene
    • Cellulitis
    • Vibrio vulnificus infection
    • Aeromonas hydrophila infection
  • Trauma
  • Deep venous thrombosis
  • Inflammatory disorders:
    • Pyoderma gangrenosum
    • Necrobiosis lipoidica

• Below, find a list of differential diagnosis for diabetic foot:

Diseases	Symptoms							Signs	Gold standard Investigation to diagnose
	History	Onset	Pain	Fever	Laterality	Scrotal swelling	Symptoms of primary disease
Diabetic foot	*History of poor glycemic control *Trauma *Burn	Chronic	+ -	+ -	Unilateral	-	Since it is related to diabetes, symptoms such as polyuria, polydipsia and polyphagia could be seen.	*Shiny skin *Decreased hair distribution *Ulcer *Signs of infection *Foot deformities such as charcot foot and hammer toe	The diagnosis of diabetic foot could be done by clinical findings, nevertheless MRI is essential to exclude the osteomyelitis.
(Cellulitis-erysipelas-skin abscess)	Acute painful swelling Fever	Acute	+	+	Unilateral	-	-	Tenderness, hotness, and may be fluctuation if abscess formed. Lymphangitis in nearby lymph nodes. Toxemia and fever in severe cases. Cellulitis involves the deeper dermis and erysipelas involves the upper dermis.	Usually it doesn't need any laboratory tests to diagnose. Blood cultures are warranted for patients in the following circumstances: Systemic toxicity Extensive skin or soft tissue involvement Underlying comorbidities persistent cellulitis In patients with recurrent cellulitis, serologic testing for beta-hemolytic streptococci is a good diagnostic tool.
Lymphatic filariasis	History of living in endemic area or travelling to it	Chronic	+	+	Bilateral	+	-	Hepatomegaly Lymphedema Elephantiasis Lymphangitis Hydrocele Scrotal elephantiasis Lymphadenopathies Rhonchi may be present in patients with Pulmonary tropical eosinophilia syndrome.	Preparing blood smears Thick smears Thick smears consist of a thick layer of dehemoglobinized (lysed) red blood cells (RBCs). Thick smears allow a more efficient detection of parasites (increased sensitivity). Thin smears consist of blood spread in a layer such that the thickness decrease. By the ultrasound, the following findings can be observed: Dilated lymphatic channels Living worms tend to be in motion which called "filarial dance" sign.
Chronic venous insufficiency	History of untreated varicose veins Painful bilateral lower limb swelling that increases with standing and decreases by rest and leg elevation.	Chronic	+	-	Bilateral	+ (If congenial)	-	Typical varicose veins Skin change distribution correlate with varicose veins sites in the medial side of ankle and leg Reduction of swelling with limb elevation.	Duplex ultrasound will demonstrate typical findings of venous valvular insufficiency
Acute deep venous thrombosis	History of prolonged recumbency Classic symptoms of DVT include acute unilateral swelling, pain, and erythema	Acute	+	-	Unilateral	-	May be associated with primary disease mandates recumbency for long duration	Dilated superficial veins Difference in calf diameter is twice as likely to have DVT(most impotant sign ) Calf pain on passive dorsiflexion of the foot (Homan's sign) isn't realiable sign.	Compression ultrasonography (CUS) with doppler is the diagnostic test of choice D-dimer level is used for unprobable cases
Lipedema	Family history especially in women; X-linked dominant or autosomal dominant condition. Abnormal deposition of fat and edema and easy bruising.	Chronic	+	-	Bilateral	-	-	Tender with palpation Negative Semmer sign to differentiate from lymphedema. Pinching the skin on the upper surface of the toes. If it is possible to grasp a thin fold of tissue then it is negative result. In a positive result, it is only possible to grasp a lump of tissue.	MRI offers strong qualitative and quantitative parameters in the diagnosis of lipedema
Myxedema	History of untreated hypothyroidism. Infiltration of the skin with glycosaminoglycans with associated water retention.	Chronic	+	-	Bilateral	-	+ (hypothyroidism )	Pretibial myxedema	Thyroid function tests.
Other causes of generalized edema	History of chronic general condition (cardiac-liver-renal)	Chronic	-	-	Bilateral	-	+		According to the primary cause ( Echo- LFTs- RFT)