The diabetic foot ulcer deserves to be treated as a distinct emergency rather than a subtype of leg ulcer. NICE NG19 asks for referral of an active diabetic foot problem within 1 working day to the multidisciplinary foot care or foot-protection service, with immediate hospital referral for limb- or life-threatening disease, because the combination of neuropathy, ischaemia and impaired immunity means an apparently trivial ulcer can progress to osteomyelitis and amputation within days — and the patient cannot feel it deteriorating. Most diabetes-related amputations are preceded by a foot ulcer, and delayed referral is a modifiable factor. Pyoderma gangrenosum is included because the reflex response to a necrotic ulcer edge — debridement — actively worsens it through pathergy, so recognising it prevents harm. Marjolin's ulcer is rare but it is why non-healing ulcers are reassessed at 12 weeks: any chronic wound can undergo malignant transformation, and the tumour is often mistaken for exuberant granulation tissue for months.

The relationship between pain and leg position is the most discriminating question in the history and costs nothing. Venous hypertension is relieved by elevation, so a venous ulcer feels better with the leg up; arterial perfusion depends on gravity, so an ischaemic leg hurts more when elevated and patients characteristically sleep in a chair or hang the leg out of bed. A patient who sleeps sitting up because of leg pain has arterial disease until proven otherwise. Nicorandil-induced ulceration is worth knowing specifically because it is drug-induced, often severe and non-healing, frequently misdiagnosed for months, and resolves completely on withdrawal of the drug — but only if someone thinks to look at the repeat prescription. Asking who actually does the dressings and whether the patient can reach their own feet changes the management plan more than any investigation.

Site and pain together identify the type in the great majority of cases before any equipment is involved: medial and better up is venous, lateral or toes and worse up is arterial, plantar and painless is neuropathic. The important subtlety is mixed disease, which is common in older patients and in diabetes and is where harm occurs — a leg can look convincingly venous, with oedema and staining, while the ABPI is 0.6. This is precisely why arterial assessment is required before strong compression rather than being a formality: the clinical appearance of a venous ulcer does not exclude significant arterial disease. In diabetes, the ABPI can additionally be falsely elevated above 1.3 by medial arterial calcification, so a high reading is also a referral trigger rather than reassurance, and toe-brachial pressures or duplex are needed instead.

The ABPI is the fulcrum of this entire pathway. Full-strength compression applied to a leg with an ABPI below 0.5 can cause pressure necrosis and has led to amputations; it is one of the clearest examples in community practice of a well-intentioned treatment causing catastrophic harm when a five-minute measurement is skipped. The technique details matter: the patient must be supine and rested, because standing or recent exertion distorts the reading, and the highest of the two brachial pressures is used as the denominator. A falsely high ABPI above 1.3 is a particular trap in diabetes and chronic kidney disease, where medial calcification makes the vessel incompressible — this reading must never be interpreted as good perfusion. Serial measurement and photography are equally important: the 12-week non-healing review which triggers reassessment and escalation can only be applied if the baseline size was recorded, and in practice the absence of a baseline measurement is why chronic ulcers drift for years.

Two investigative habits cause most of the avoidable harm in leg ulcer care, and both involve doing more rather than less. Routine wound swabbing generates positive cultures from colonising flora in almost every chronic ulcer, which in turn generates repeated antibiotic courses that do not improve healing and do drive resistance and C. difficile. Infection in an ulcer is a clinical diagnosis — increasing pain, spreading erythema, purulence, systemic upset — and swabs are not taken routinely at presentation — a sample after cleaning is considered only if infection worsens or fails to improve (NICE NG152). The second habit is antimicrobial and advanced dressings in place of compression: the evidence consistently shows that dressing choice has a marginal effect on healing while compression has a large one, so a simple non-adherent dressing under proper compression outperforms an expensive dressing without it. Biopsy technique also matters: the diagnostic tissue in a malignant ulcer is at the raised edge, and a biopsy taken from the necrotic centre is commonly non-diagnostic.

Two referrals are systematically under-made. The first is the vascular referral for venous intervention: NICE CG168 recommends referring people with a venous leg ulcer, or a healed venous leg ulcer, to a vascular service for assessment and consideration of intervention, because correcting the underlying venous incompetence can reduce recurrence — yet most ulcers are managed indefinitely with dressings alone and never reach a vascular clinic. The second is reassessment, biopsy or skin cancer referral for the atypical or non-progressing ulcer. The 12-week review matters because squamous cell carcinoma arising in chronic ulceration is typically diagnosed late, after months or years of dressing changes, and by then it may have metastasised; the tumour can look identical to exuberant granulation tissue. Applying both rules requires only that the ulcer's size was measured at the start and that someone reviews the whole plan at 12 weeks, which is a diary entry rather than a clinical skill.

Compression is one of the most effective interventions in community medicine and one of the most frequently under-dosed. The evidence for strong graduated compression is strong and consistent, while the comparative evidence between dressing types is weak — which means the expensive part of most ulcer care contributes least. Under-dosed compression is a common reversible cause of a non-healing venous ulcer, and tolerance often improves with good analgesia — but increasing pain or new numbness under compression must be reassessed the same day, not persisted with. Topical antibiotics deserve a specific warning: they achieve little, and neomycin and framycetin are potent sensitisers, so a proportion of patients with persistent peri-ulcer eczema have iatrogenic contact dermatitis. Where arterial disease is found, the ulcer is a marker of widespread atherosclerosis, and the statin and antiplatelet will do more for the patient's life expectancy than any dressing will.

Once a venous ulcer has healed, the clinical problem changes from healing to prevention, and compression hosiery is the intervention with the best evidence, and concordance is the main determinant of success. Concordance in turn depends on practical details that are easy to overlook: whether the patient can physically pull the stocking on (an applicator or a lower class worn consistently beats a higher class abandoned in a drawer), whether they have two pairs so one can be washed, and whether replacement is actually organised. Note that graduated compression stockings are not recommended for the prevention of post-thrombotic syndrome after DVT, which is a different indication — the evidence here is specifically about preventing ulcer recurrence. The psychosocial burden is also routinely under-addressed: pain, exudate and odour drive social withdrawal and depression, and community leg clubs improve healing rates partly through peer support and adherence.

The four-week review is a useful prognostic point: wounds without clear progress in the first month are unlikely to heal on the current plan, and this is the moment to re-examine the diagnosis rather than to continue for another six months of dressings. Persistent or increasing pain under compression must always be treated as a warning rather than as expected discomfort — it is the presentation of pressure damage from bandaging on an under-recognised ischaemic limb, and the correct action is to remove the bandage and reassess the same day. Repeating the ABPI when the clinical picture changes matters because peripheral arterial disease progresses, and a leg that was safe to compress a year ago may no longer be. Finally, the 12-week review should be booked at the first appointment: the reason Marjolin's ulcers are diagnosed late is almost never a failure of knowledge, but the absence of a scheduled point at which someone steps back and asks why the wound is still there.