Approach to Leg Ulcers
On this page
Direct answer
A leg ulcer is a breach of skin below the knee that fails to heal within about six weeks, and most are venous, arterial or neuropathic in origin. Venous ulcers sit around the medial malleolus with oedema and palpable pulses, while arterial ulcers are painful and have a low ankle-brachial pressure index. Measuring that index before compression is the most important step, because compression can harm an ischaemic limb.
What you must remember
- Venous ulcer: the gaiter area above the medial malleolus, shallow and irregular, with oedema, varicosities and haemosiderin staining.
- Arterial ulcer: painful, punched-out and typically on the toes, lateral malleolus or pressure points, with cold, pale skin and weak or absent pulses.
- Neuropathic ulcer: painless and sited over pressure points on the plantar surface, often in diabetes with a sensory deficit.
- Vasculitic ulcer: painful, with palpable purpura, necrosis and a punched-out outline, and possibly several lesions at once.
- ABPI: an ankle-brachial pressure index above 0.8 favours venous disease, and values below about 0.5 generally rule out standard compression.
- Malignancy: squamous cell carcinoma, the Marjolin ulcer, arises in long-standing ulcers with a raised, everted edge and needs biopsy.
- Diabetes check: HbA1c and a foot examination are essential, because diabetic ulcers often coexist with arterial disease.
- Venous care: graduated compression, elevation and moist dressings form the mainstay of venous ulcer treatment.
A systematic assessment before any dressing
A 67-year-old man has a six-month ulcer above the left medial malleolus, with ankle swelling and brown staining of the surrounding skin. Before compression is applied, the clinician must confirm that the arterial supply is adequate.
- Take the history: duration, pain, previous ulcers, deep vein thrombosis, diabetes and smoking shape the differential diagnosis and the risk of each cause.
- Examine the limb: check the pulses, skin colour, oedema, varicosities and sensation, since each finding points to a different aetiology and treatment.
- Measure the ABPI: ratios above 0.8 favour venous disease, while values below about 0.5 contraindicate standard compression and call for vascular review.
- Image the veins: duplex ultrasound maps reflux in the superficial and deep venous systems, which guides whether venous surgery or intervention is appropriate.
- Biopsy the atypical ulcer: an irregular ulcer with a rolled edge, or one unresponsive to six weeks of standard care, needs biopsy to exclude squamous cell carcinoma or vasculitis.
- Match the treatment to the cause: graduated compression for venous disease, revascularisation review for arterial disease, and offloading for neuropathic ulcers.
Where the exam tries to catch you
Three traps appear in almost every leg ulcer question.
- Trap: applying compression to a painful ulcer with cold toes. Correct: a painful ulcer with reduced pulses is arterial, and compression can worsen ischaemia, so the ABPI comes first.
- Trap: calling every chronic ulcer venous. Correct: neuropathic, vasculitic and malignant ulcers mimic venous disease, so the pattern and the pulses must be checked.
- Trap: ignoring an ulcer whose edges are raised and everted. Correct: these features suggest squamous cell carcinoma arising in a chronic ulcer, which needs biopsy.
Frequently asked questions
Which ankle-brachial pressure index suggests venous disease in a leg ulcer?
An ankle-brachial pressure index above 0.8 favours a venous rather than arterial cause for a leg ulcer. Values below about 0.5 generally rule out standard compression therapy in most patients.
Why are painful leg ulcers with weak pulses not treated with compression?
Painful leg ulcers with weak pulses are usually arterial, and compression raises the pressure within an already ischaemic limb. Arterial ulcers therefore need arterial assessment and revascularisation review before any compression is considered.
What is a Marjolin ulcer?
A Marjolin ulcer is a squamous cell carcinoma that arises within a long-standing chronic ulcer. Clues include a raised, everted edge, a change in colour or granulation, and failure to heal despite standard treatment, all of which justify a biopsy.
Which investigations are needed for a non-healing diabetic leg ulcer?
HbA1c, a neuropathy assessment and an ABPI check are the core investigations for a non-healing diabetic leg ulcer. Diabetic ulcers often coexist with arterial disease, so vascular assessment is needed even when the ulcer looks neuropathic. Calcified diabetic vessels can give a falsely high ABPI.