Dry gangrene

Overview

Tissue death from gradual arterial ischaemia - desiccated, sterile, mummified necrosis. The key exam discriminator is dry (sterile, stable) vs wet (infected, emergency).

Aetiology

•Most common: atherosclerotic peripheral arterial disease (PAD) - gradual stenosis → coagulative necrosis → desiccation → mummification

•Other causes: frostbite, arterial embolism (AF, post-MI mural thrombus), severe Raynaud's phenomenon

•Risk factors: older age, diabetes mellitus, smoking, hypertension, hyperlipidaemia

Presentation

•Skin colour change - pale → dusky purple → black as haemoglobin degrades

•Mummification - tissue becomes dry, shrunken, hard, leathery

•Demarcation line - clear boundary between viable and necrotic tissue, rim of erythema on viable side

•No systemic features of infection - apyrexial, haemodynamically stable, odourless

•Absent/reduced pedal pulses, cold extremity, prolonged capillary refill

•Background: rest pain (especially nocturnal), non-healing ulcers, history of PAD/diabetes/smoking

🚨

Foul smell, spreading erythema, systemic sepsis, or crepitus = conversion to wet gangrene or gas gangrene - surgical emergency.

Investigations

🥇 First-line

•ABPI - <0.9 confirms PAD; <0.5 = critical limb ischaemia; falsely elevated (>1.3) in calcified diabetic vessels

•Bloods - FBC, CRP (exclude infection), glucose/HbA1c, lipids, U&E

•Duplex ultrasound of lower limb arteries - non-invasive, identifies site/degree of stenosis

•ECG - screen for AF as embolic source

🏆 Gold standard

•CT angiography (CTA) - detailed arterial mapping for revascularisation planning

🥈 Second-line

•MR angiography - if contrast contraindicated (e.g. significant renal impairment)

Differential Diagnosis

•Wet gangrene - infected, moist, spreading necrosis, systemic sepsis, ill-defined demarcation

•Gas gangrene (clostridial myonecrosis) - crepitus on palpation, rapidly fatal, surgical emergency

•Necrotising fasciitis - spreads along fascial planes, systemic sepsis, pain out of proportion, crepitus

•Pyoderma gangrenosum - violaceous undermined edges, not true gangrene, associated with IBD/rheumatoid arthritis

•Calciphylaxis - ischaemic skin necrosis in renal failure, affects trunk/thighs rather than digits

Management

•Urgent vascular surgery referral - goal is revascularisation to restore blood supply and prevent conversion to wet gangrene

•Allow autodemarcation - do NOT amputate prematurely; waiting defines the boundary between viable and non-viable tissue, minimising amputation level

•Revascularisation - angioplasty/stenting or surgical bypass (e.g. femoropopliteal bypass) depending on anatomy

•Amputation - once demarcation is complete (digit, ray, or more proximal depending on extent)

•Cardiovascular risk factor optimisation - statin, antiplatelet therapy, antihypertensives, smoking cessation, glycaemic control

⚠️

Do not rush to amputate dry gangrenous tissue before autodemarcation - premature surgery risks removing potentially salvageable tissue.

Complications

•Conversion to wet gangrene - superadded infection → systemic sepsis, life-threatening emergency

•Amputation - loss of digit/foot/limb with reduced mobility

•Cardiovascular events - underlying atherosclerosis → high rates of MI and stroke; drives long-term mortality

Dry vs Wet Gangrene

Dry vs wet gangrene

Feature	Dry gangrene	Wet gangrene
Infection	Sterile	Bacterial superinfection
Tissue appearance	Dry, mummified, hard	Moist, swollen, soft
Odour	Odourless	Foul-smelling
Demarcation	Well-defined	Ill-defined
Systemic sepsis	Absent	Present
Urgency	Urgent (not emergency)	Surgical emergency