About This Page
This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
The Bottom Line
- Do not culture or prescribe antibiotics for a chronic ulcer unless there are clinical signs of infection: redness, warmth, swelling, increasing pain, purulence, fever, or systemic illness
- Classify ulcers by location and physiology: venous gaiter-area shallow exudative, arterial punched-out painful distal, neuropathic plantar pressure point, pressure injury over bony prominence
- Every non-healing ulcer needs vascular assessment, including pulses and ankle-brachial index where appropriate, before compression or debridement decisions
- Biopsy ulcers that are atypical, rolled/everted, excessively painful, violaceous, undermined, rapidly enlarging, or not healing despite appropriate care
- Diabetic foot ulcers require offloading, vascular assessment, infection assessment, glycaemic optimization, and osteomyelitis consideration
Approach to the Presentation
A skin ulcer is a loss of epidermis and dermis with impaired healing. The MCCQE1 approach is to identify cause and complications rather than simply choose a dressing. Start with duration, location, pain, exudate, odour, trauma, diabetes, neuropathy, vascular disease, smoking, immobility, pressure exposure, immunosuppression, inflammatory bowel disease, autoimmune symptoms, medications, and previous skin cancer. Examine wound size, depth, edge, base, undermining, surrounding skin, oedema, pulses, capillary refill, sensation, footwear, bony prominences, and infection signs. Distinguish colonization from infection: many chronic ulcers culture bacteria, but antibiotics are indicated only when clinical infection is present. Compression for venous ulcers is effective but unsafe if significant arterial disease has not been excluded.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Arterial Insufficiency Ulcer / Critical Limb Ischaemia | must-not-miss | Painful punched-out distal ulcer on toes/foot, cool limb, reduced pulses, dependent rubor, elevation pallor, rest pain, smoking/diabetes/PAD | ABI/toe pressures and arterial duplex/CTA; urgent vascular referral if critical ischaemia |
| Diabetic Foot Ulcer with Infection or Osteomyelitis | must-not-miss | Plantar pressure-point ulcer, neuropathy, callus, deformity; infection signs, probe-to-bone, systemic illness, poor glycaemic control | Probe-to-bone, ESR/CRP, X-ray initially, MRI if osteomyelitis suspected; deep tissue culture after debridement if infected |
| Skin Cancer in Chronic Wound (SCC/Marjolin ulcer, BCC, melanoma) | must-not-miss | Non-healing, rolled/everted edge, bleeding, excessive granulation, new pain, growth in scar/burn/radiation site, atypical pigmentation | Biopsy of ulcer edge/base |
| Necrotizing Soft-Tissue Infection | must-not-miss | Severe pain out of proportion, fever/toxicity, rapid progression, bullae, crepitus, skin anaesthesia, shock | Clinical diagnosis; urgent surgical exploration, do not wait for imaging |
| Venous Leg Ulcer | common | Shallow irregular ulcer in gaiter area/medial malleolus, oedema, varicosities, hemosiderin staining, lipodermatosclerosis, exudate; aching improves with elevation | ABI before compression; venous duplex if recurrent/complex |
| Pressure Injury | common | Ulcer over sacrum, heel, trochanter, malleolus, or other bony prominence; immobility, frailty, spinal cord injury, poor nutrition | Clinical staging; assess nutrition, mobility, continence, support surfaces |
| Neuropathic Non-Diabetic Ulcer | common | Painless pressure-point ulcer in neuropathy from alcohol, B12 deficiency, spinal disease, leprosy rare, or other neuropathy | Monofilament/vibration testing; neuropathy workup guided by history |
| Pyoderma Gangrenosum | less common | Very painful rapidly expanding ulcer with violaceous undermined border; pathergy after trauma/debridement; associated IBD, arthritis, haematologic disease | Clinical diagnosis of exclusion; biopsy to exclude infection/malignancy; dermatology/rheumatology |
| Vasculitic Ulcer | less common | Painful purpura, livedo, necrosis, multiple ulcers, systemic symptoms, renal/neurological features, autoimmune disease | Urinalysis, creatinine, CBC, ESR/CRP, autoimmune serology; skin biopsy with DIF |
| Infectious Ulcer (ecthyma, atypical mycobacteria, deep fungal, leishmaniasis) | less common | Purulent crusted ulcer, exposure history, travel, water/aquarium exposure, immunosuppression, nodular lymphangitis | Tissue culture/biopsy for bacterial, mycobacterial, fungal, or parasitic testing based on exposure |
| Factitial or Self-Inflicted Ulcer | rare | Geometric or accessible lesions, inconsistent history, psychiatric comorbidity, recurrent unexplained wounds | Diagnosis after exclusion; compassionate, non-accusatory assessment |
Red Flags & Key History
Symptoms
Rest pain, severe night pain, toe/foot ulcer, smoking, diabetes, known PAD — critical limb ischaemia
Diabetes with spreading erythema, warmth, swelling, purulence, fever, probe-to-bone, or systemic illness
Severe pain out of proportion, rapidly spreading skin change, bullae, crepitus, shock
Non-healing despite appropriate care, rolled/everted edge, bleeding, new pigmentation, or growth in old scar/burn
Very painful ulcer with violaceous undermined border and worsening after debridement — pyoderma gangrenosum
Oedema, varicosities, heaviness improved with elevation — venous disease
Immobility, incontinence, malnutrition, wheelchair/bed dependence — pressure injury risk
Signs
Absent pulses, cool limb, delayed capillary refill, dependent rubor, elevation pallor
Probe-to-bone, deep sinus, exposed tendon/bone, spreading cellulitis
Necrosis, haemorrhagic bullae, crepitus, skin anaesthesia
Rolled border, excessive granulation, friable bleeding tissue
Gaiter-area shallow exudative ulcer with hemosiderin and lipodermatosclerosis
Sacral/heel ulcer over pressure point
Approach to Investigation
First-line
Wound and vascular assessmentMeasure length/width/depth, edge/base/exudate/odour, surrounding skin, oedema, pulses, capillary refill, neuropathy, footwear, pressure points, and pain
Ankle-brachial index or toe pressuresEssential before compression and for suspected PAD. Toe pressures are useful when diabetes/calcified vessels make ABI falsely high
Clinical infection assessmentCulture is not routine for uninfected ulcers. If infected, obtain deep tissue culture after cleansing/debridement when feasible, not a superficial swab alone
Diabetic foot assessmentMonofilament/vibration testing, glucose/A1c, renal function, footwear, deformity, and offloading needs
Second-line
X-ray and MRI for suspected osteomyelitisX-ray first for bone destruction/gas/foreign body; MRI if osteomyelitis remains suspected
BiopsyFor atypical, non-healing, rolled-edge, pigmented, violaceous, rapidly progressive, or treatment-resistant ulcers to exclude malignancy, vasculitis, infection, or pyoderma gangrenosum
Venous duplex or arterial imagingVenous duplex for recurrent/complex venous ulcers; arterial duplex/CTA/MRA if PAD or critical limb ischaemia suspected
Specialist
Vascular surgeryUrgent for critical limb ischaemia, rest pain, gangrene, rapidly worsening arterial ulcers, or non-healing ulcer with significant PAD
Interprofessional wound/diabetic foot teamFor diabetic foot ulcers, pressure injuries, complex wounds, recurrent ulcers, offloading, orthotics, debridement, and dressing planning
Dermatology/rheumatologyFor suspected pyoderma gangrenosum, vasculitis, atypical ulcers, inflammatory disease, or biopsy planning
Management Principles
Choosing Wisely Canada dermatology recommendations + Canadian wound-care practice principles1
General wound principles
- Treat the cause, not just the wound: venous hypertension, arterial insufficiency, pressure, neuropathy, infection, inflammation, malignancy, nutrition, and smoking
- Cleanse, debride non-viable tissue when appropriate, maintain moisture balance, protect surrounding skin, manage pain, and measure progress serially
- Do not routinely culture or use antibiotics for a chronic ulcer without clinical infection
2
Venous ulcers
- Compression therapy is central only after significant arterial disease is excluded
- Leg elevation, calf-muscle activation, oedema management, appropriate dressings, and venous intervention referral for selected recurrent disease
- Manage dermatitis around the ulcer with emollients and topical anti-inflammatory therapy as appropriate
3
Arterial and diabetic ulcers
- Arterial ulcer/critical limb ischaemia: urgent vascular assessment, risk-factor modification, antiplatelet/statin as indicated, smoking cessation, revascularization assessment
- Diabetic foot ulcer: offload pressure, optimize glycaemia, assess vascular supply, treat infection, evaluate osteomyelitis, podiatry/orthotics involvement
- Avoid aggressive debridement of dry stable arterial eschar until perfusion is addressed unless infection mandates urgent action
4
Atypical or malignant ulcers
- Biopsy non-healing or atypical ulcers rather than repeating dressings indefinitely
- Avoid surgical debridement in suspected pyoderma gangrenosum until specialist assessment because pathergy can worsen disease
- Refer for dermatology, vascular, infectious diseases, or oncology based on ulcer physiology and biopsy results
Complications & Pitfalls
- Superficial swab of every ulcer: Colonization is common; culture and antibiotics should be guided by clinical infection.
- Compression without ABI: Significant arterial disease can make compression dangerous.
- Repeated antibiotics for venous dermatitis: Bilateral erythema and oedema are often inflammatory, not cellulitis.
- Failure to biopsy: SCC, BCC, melanoma, vasculitis, and pyoderma gangrenosum can masquerade as chronic wounds.
- Debriding pyoderma gangrenosum aggressively: Pathergy can enlarge the ulcer.
- No offloading in diabetic foot ulcer: Dressings alone will fail if pressure continues.
MCCQE1 Exam Tips
- 1Venous ulcer: medial gaiter area, oedema, hemosiderin, shallow exudative wound; treat with compression after ABI
- 2Arterial ulcer: painful punched-out distal ulcer with reduced pulses; vascular assessment is the next best step
- 3Diabetic foot ulcer management always includes offloading plus vascular and infection assessment
- 4Probe-to-bone or chronic deep diabetic ulcer should make osteomyelitis likely
- 5Do not culture uninfected chronic ulcers; Choosing Wisely Canada emphasizes avoiding low-value cultures/antibiotics
- 6A non-healing ulcer with rolled edge or excessive granulation needs biopsy to exclude SCC or other malignancy
- 7Very painful violaceous undermined ulcer after minor trauma = pyoderma gangrenosum; avoid debridement until specialist review
- 8Pain out of proportion plus bullae or systemic toxicity = necrotizing infection; urgent surgery is the answer
practicetest your knowledge on skin ulcer / non-healing woundApply what you've learnt with MCCQE1-style questions from the iatroX Q-Bank — dermatologic and beyond.
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