Causes of Gangrene in the Leg

Types of Gangrene (Pathological Classification)

1. Occlusive Arterial Disease (Most Common Cause)

A. Atherosclerosis (Peripheral Arterial Disease / PAD)

• Most common cause of gangrene in the lower limb overall
• Affects men > women; older age group (typically >55 years)
• Risk factors: smoking, hypertension, hyperlipidaemia, diabetes mellitus
• Affects large and medium vessels - aortoiliac, femoral, popliteal, crural
• Progresses from intermittent claudication → rest pain → ischaemic ulceration → gangrene (Chronic Limb-Threatening Ischaemia / CLTI)
• Typically produces dry gangrene
• • Bailey and Love's Short Practice of Surgery, 28th Ed., p. 1030

B. Arterial Embolism

• Sudden onset; patient feels severe pain radiating down the course of the artery
• Sources include cardiac emboli (atrial fibrillation, mural thrombus post-MI, valvular disease), aortic aneurysm, paradoxical embolism
• Gangrene usually unilateral
• • S Das Manual of Clinical Surgery, 13th Ed.

C. Arterial Thrombosis

• Acute-on-chronic occlusion in a vessel already stenosed by atherosclerosis
• Less dramatic than embolism but still causes acute limb ischaemia

2. Thromboangiitis Obliterans (Buerger's Disease)

• Non-atherosclerotic, segmental inflammatory thrombotic disease of small and medium vessels
• Strongly associated with heavy tobacco use (smoking is near-mandatory for diagnosis)
• Affects young men <45 years
• Affects both upper and lower extremities (at least 2 limbs); 40% have all four limbs involved
• Starts distally (feet/hands) and progresses proximally
• Presents with foot claudication, Raynaud's phenomenon, superficial thrombophlebitis, then ischaemic ulcers and gangrene
• • Current Surgical Therapy 14e, p. 1191+

3. Diabetes Mellitus (Diabetic Gangrene)

1. Macrovascular disease - atherosclerosis typically affecting crural (tibial) vessels
2. Peripheral sensorimotor neuropathy (PSN) - stocking distribution sensory loss leads to unnoticed injury and neglect; motor involvement causes foot deformity and abnormal pressure loading
3. Immunosuppression from hyperglycaemia - predisposes to infection that spreads rapidly in subfascial planes

• Can start from trivial trauma (careless nail-trimming, minor infection)
• Can be unilateral or bilateral
• Superadded infection leads to fulminant foot sepsis and death
• • Bailey and Love's Short Practice of Surgery, 28th Ed., p. 1031

4. Infective / Microbial Causes

A. Gas Gangrene (Clostridial Myonecrosis)

• Caused primarily by Clostridium perfringens (spores in soil)
• Requires anaerobic conditions (devitalised tissue, contaminated wounds)
• Rapid and massive muscle necrosis with gas production, exotoxins causing systemic toxaemia
• Surgical emergency - requires radical debridement ± amputation, IV penicillin, hyperbaric oxygen
• • Bailey and Love's, 28th Ed.; Campbell's Operative Orthopaedics 15th Ed.

B. Synergistic Gangrene (Meleney's)

• Mixed infection with synergistic organisms (microaerophilic Streptococcus + Staphylococcus)
• Slowly progressive; begins as wound infection, spreads to cause full-thickness skin and fascial necrosis
• • Bailey and Love's Short Practice of Surgery, 28th Ed.

C. Necrotising Fasciitis

• Rapidly spreading infection along fascial planes; mixed aerobic-anaerobic organisms
• "Flesh-eating" infection - can rapidly compromise limb viability

5. Trauma

A. Direct Vascular Injury

• Lacerations, crush injuries, or fractures damaging arterial supply
• Compartment syndrome following trauma can cause ischaemia of the leg compartments

B. Prolonged Compression / Pressure

• Bedsores / pressure ulcers over bony prominences (heel, malleolus) can progress to gangrene - Bailey and Love's, 28th Ed., p. 1031

C. Crush Syndrome

• Prolonged muscle crushing causes reperfusion injury on release, leading to microvascular compromise and potential gangrene

D. Frostbite

• Prolonged cold exposure causes ice crystal formation, endothelial injury, thrombosis, and distal gangrene
• History of cold exposure is key

6. Vasospastic Conditions

Raynaud's Phenomenon / Disease

• Episodic digital artery spasm: pallor → cyanosis → erythema
• Raynaud's disease (primary) affects young women; mainly upper limbs but can affect toes
• Repeated ischaemic episodes lead to superficial ulceration and tip gangrene
• Secondary Raynaud's (associated with systemic sclerosis, SLE, etc.) is a more common cause of gangrene

7. Vasculitis

• Rheumatoid vasculitis: small vessel involvement causes digital gangrene and leg ulcers
• Polyarteritis nodosa
• ANCA-associated vasculitis (GPA, microscopic polyangiitis)
• Anti-phospholipid syndrome: peripheral arterial thrombosis → digital gangrene

8. Haematological / Hypercoagulable States

• Polycythaemia vera - hyperviscosity and thrombosis
• Anti-phospholipid syndrome (APS) - arterial and venous thrombosis
• Disseminated intravascular coagulation (DIC) - microthrombi in small vessels → symmetrical peripheral gangrene
• Cryoglobulinaemia - cold-induced protein precipitation causing microvascular occlusion
• Homocysteinaemia - accelerates atherosclerosis and promotes thrombosis

9. Prolonged Vasopressor / Drug Use

• Prolonged use of peripheral vasoconstrictors (e.g. high-dose vasopressors in ICU - noradrenaline, dopamine) can cause distal limb ischaemia and gangrene
• Ergotamine toxicity
• • Current Surgical Therapy 14e, p. 1191

10. Neoplasm

• Osteogenic sarcoma and other tumours can compromise local vascularity and necessitate amputation due to secondary gangrene
• • Bailey and Love's, 28th Ed.

Summary Table

• In the lower limb, PAD is the single most common cause (Current Surgical Therapy 14e)
• Diabetes acts as a force multiplier - it worsens atherosclerosis, impairs sensation, and cripples immune defence simultaneously
• Buerger's disease is the cause to suspect in young smokers with distal foot ischaemia
• Gas gangrene is a surgical emergency - any crepitus in a diabetic foot must be treated urgently
• Gangrene due to embolism tends to be sudden-onset and unilateral; atherosclerotic gangrene is gradual and often bilateral