Differentials
Diabetic foot ulcer
SIGNS / SYMPTOMS
History of diabetes. Foot wounds occur in the presence of peripheral neuropathy secondary to repetitive stress.
Ulcers form on the plantar aspect of the foot or on the dorsal aspect of the digits from repetitive moderate stress.
INVESTIGATIONS
In the presence of concomitant diabetes and neuropathy, wound location is often the defining factor.
Fasting plasma glucose ≥7 mmol/L (≥126 mg/dL) is diagnostic of diabetes.
Arterial ulcer
SIGNS / SYMPTOMS
History of peripheral arterial disease.
Ulcers secondary to arterial insufficiency are located on the distal margins of the foot and are frequently gangrenous or 'punched out' in appearance.
INVESTIGATIONS
Non-invasive vascular studies may help to exclude peripheral arterial disease, although wounds of mixed aetiology are not uncommon.
A Doppler-derived ankle-brachial index <0.92 is abnormal. If foot pulses are absent or diminished, the ankle-brachial index is <0.8 and the patient has foot or leg ulcers.
More detailed arterial imaging such as duplex arterial ultrasound can be performed to document the level and degree of arterial obstruction.
Squamous cell carcinoma (Marjolin)
SIGNS / SYMPTOMS
Long-standing non-healing wound with irregular edges.
INVESTIGATIONS
Skin biopsy is diagnostic of squamous cell carcinoma.
Pyoderma gangrenosum
SIGNS / SYMPTOMS
Wound may increase in size and inflammation after surgical debridement (pathergy).
INVESTIGATIONS
Skin biopsy is diagnostic of pyoderma gangrenosum.
Kaposi's sarcoma
SIGNS / SYMPTOMS
History of immunosuppression (e.g., HIV infection, organ transplantation, immunosuppressive therapies).
Raised purplish lesions that may be confused with venous lesions.
INVESTIGATIONS
Skin biopsy is diagnostic of Kaposi's sarcoma.
Lymphoedema
SIGNS / SYMPTOMS
Usually unilateral.
Characterised by a dorsal foot buffalo hump and loss of the web spaces between the toes (Stemmer's sign).
INVESTIGATIONS
Duplex ultrasound is normal or minimally abnormal.
Congestive heart failure
SIGNS / SYMPTOMS
History of dyspnoea (on minimal exertion, orthopnoea, paroxysmal nocturnal dyspnoea) and weight gain.
Bilateral pitting oedema with blebs and bullae in severe cases. Ulceration is rare.
INVESTIGATIONS
Chest x-ray: cardiomegaly, bilateral lower lobe shadowing, pleural effusion, enlarged hilar vessels, upper lobe diversion, fluid in horizontal fissure, Kerley B lines.
Echocardiogram: systolic and diastolic dysfunction, evidence of underlying cause.
Renal disease
SIGNS / SYMPTOMS
Bilateral oedema. Ulceration is rare.
INVESTIGATIONS
Serum electrolytes: elevated potassium.
Serum urea and creatinine: elevated.
Urinalysis: possible haematuria and proteinuria.
Hepatic disease
SIGNS / SYMPTOMS
Bilateral oedema. Ulceration is rare.
INVESTIGATIONS
Liver function tests: results depend on underlying cause.
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