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Painful swollen leg

Medicine > Cardiovascular

Differential Diagnosis Schema 🧠

Vascular Causes

  • Deep vein thrombosis (DVT): Unilateral leg swelling, pain, erythema, and warmth; often associated with immobility, recent surgery, or malignancy.
  • Chronic venous insufficiency: Leg swelling, varicose veins, skin changes such as hyperpigmentation or ulceration; typically worsens with prolonged standing.
  • Cellulitis: Erythema, warmth, tenderness, and swelling; may have associated systemic symptoms such as fever.
  • Peripheral arterial disease: Painful leg, especially on exertion (claudication); may present with cool, pale skin, and diminished pulses.

Lymphatic Causes

  • Lymphedema: Chronic, progressive swelling often affecting one or both legs; pitting oedema initially, but may become non-pitting over time.
  • Lymphangitis: Red streaks extending from an infection site towards regional lymph nodes; associated with swelling, pain, and systemic symptoms.

Musculoskeletal Causes

  • Muscle strain or tear: Localised swelling, pain, and tenderness; often related to recent physical activity or trauma.
  • Compartment syndrome: Severe pain, tightness, and swelling in the leg, especially after trauma; requires urgent medical attention.
  • Baker’s cyst rupture: Swelling and pain behind the knee, which may extend down the leg; can mimic DVT.

Systemic Causes

  • Heart failure: Bilateral leg swelling, often worse in the evening; associated with dyspnoea, orthopnoea, and jugular venous distension.
  • Nephrotic syndrome: Generalised swelling, including leg oedema; associated with proteinuria and hypoalbuminaemia.
  • Liver cirrhosis: Bilateral leg swelling with associated ascites, jaundice, and signs of chronic liver disease.
  • Hypoalbuminemia: Generalised oedema due to low serum albumin, often seen in malnutrition, chronic illness, or renal disease.

Infectious Causes

  • Septic arthritis: Sudden onset of severe pain, swelling, and restricted movement in the affected joint; commonly affects the knee.
  • Osteomyelitis: Localised pain, swelling, and tenderness over the bone; may have a history of trauma or recent infection.
  • Erysipelas: A form of cellulitis with well-demarcated, raised borders; associated with systemic symptoms such as fever.

Key Points in History 🥼

Onset and Duration

  • Acute onset: Suggests DVT, cellulitis, or trauma-related conditions.
  • Chronic or progressive: More consistent with chronic venous insufficiency, lymphedema, or systemic causes like heart failure.
  • Intermittent symptoms: May suggest a Baker’s cyst or early-stage chronic venous insufficiency.

Location and Extent of Swelling

  • Unilateral swelling: Commonly associated with DVT, cellulitis, or musculoskeletal injury.
  • Bilateral swelling: Suggests systemic causes such as heart failure, nephrotic syndrome, or liver disease.
  • Localised swelling: May indicate a Baker’s cyst, muscle strain, or compartment syndrome.

Associated Symptoms

  • Fever and malaise: Suggestive of an infectious cause such as cellulitis, lymphangitis, or septic arthritis.
  • Dyspnoea or orthopnoea: Points towards heart failure as the underlying cause.
  • Pain on walking or exercise: May indicate peripheral arterial disease or DVT.
  • Skin changes (e.g., ulcers, discolouration): Suggests chronic venous insufficiency or lymphedema.
  • Redness and warmth: Typically associated with cellulitis, DVT, or compartment syndrome.

Background

  • Previous history of DVT or thrombophilia: Increases the likelihood of recurrent DVT.
  • Recent surgery or immobilisation: Important risk factors for DVT.
  • History of venous insufficiency or varicose veins: Predisposes to chronic venous insufficiency or venous ulcers.
  • Medication history: Certain medications like oral contraceptives or hormone replacement therapy can increase the risk of DVT.
  • Social history: Consider occupational factors, recent travel, and lifestyle factors that may influence the differential diagnosis.

Possible Investigations 🌡️

Imaging

  • Doppler ultrasound: First-line investigation for suspected DVT, assessing venous flow and compressibility.
  • CT venography: May be used when ultrasound results are inconclusive or in cases of suspected pelvic vein thrombosis.
  • MRI: Useful in assessing soft tissue and musculoskeletal causes such as compartment syndrome or Baker’s cyst.
  • X-ray: Typically used to assess for fractures or bony abnormalities in cases of trauma.

Laboratory Tests

  • D-dimer: Elevated in DVT, although not specific; useful in conjunction with clinical assessment and imaging.
  • FBC and CRP: Elevated white cell count and CRP suggest an infectious cause like cellulitis.
  • U&E and creatinine: Assesses renal function, which is particularly important in systemic causes of oedema.
  • Liver function tests: Used to assess liver disease in cases of suspected cirrhosis or hypoalbuminemia.
  • Coagulation profile: Important in assessing patients with suspected clotting disorders or those on anticoagulant therapy.

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Cardiovascular