Leg swelling must never be assumed to be due to peripheral oedema. A definite diagnosis of the underlying cause must be made and a careful history and examination, along with appropriate confirmatory tests, is essential. Swelling of the legs may be either unilateral or bilateral:

• Bilateral swelling is usually due to systemic conditions, e.g. cardiac failure, and unilateral is often due to local trauma, venous disease or lymphatic disease.
• Unilateral leg swelling is more often due to local causes, e.g. deep vein thrombosis, but bilateral swelling from systemic causes may be much more obvious on one side than the other, and therefore appears to be unilateral swelling.

Causes

• Local:
  • Acute:
    • Trauma
    • Deep vein thrombosis
    • Cellulitis
    • Allergic reaction
    • Rheumatoid arthritis
  • Chronic:
    • Venous: Varicose veins, obstruction of venous return, e.g. pregnancy, pelvic tumours, inferior vena cava obstruction, post-phlebitis
    • Lymphoedema: Lymphatic obstruction due to malignancy, post-irradiation, surgery, recurrent infection, lymphatic hypoplasia (Milroy's syndrome), filariasis
    • Congenital malformations, e.g. arteriovenous fistula
    • Stasis: paralysis, poor mobility and dependency, obesity
• Systemic:
  • Congestive cardiac failure
  • Hypoproteinaemia, e.g. liver failure, nephrotic syndrome, malnutrition, protein-losing enteropathy
  • Renal failure
  • Fluid overload
  • Anaemia
  • Drugs, e.g. calcium antagonists, non-steroidal anti-inflammatory drugs
  • Hypothyroidism
  • Hereditary angioneurotic oedema

Presentation

The nature of the presentation will give essential clues in establishing the diagnosis in terms of whether unilateral or bilateral, speed of onset (see list of causes above) and associated symptoms, e.g.:

• Orthopnoea, paroxysmal nocturnal dyspnoea: Heart failure
• Diarrhoea or other bowel dysfunction: Protein-losing enteropathy
• Painful swollen calf: deep vein thrombosis or inflammation, e.g. cellulitis, osteomyelitis
• Pigmentation: Venous insufficiency
• Immobility
• Periorbital oedema: Renal failure
• Pelvic mass or pregnancy

Investigations

• Urinalysis: Proteinuria suggests renal cause
• Full blood count: High white cell count in infection; anaemia
• Biochemistry: Renal function and electrolytes (raised creatinine in renal failure); liver function tests (impaired liver function and associated low albumin); glucose (infection associated with diabetes); thyroid function tests (hypothyroidism)
• Clotting screen: Abnormal clotting associated with spontaneous haematoma
• Chest X-ray: Pulmonary oedema
• D-dimer blood test: D-dimers are products of fibrin degradation and are raised in patients with venous thromboembolism. Sensitivity of the test is high but specificity is poor.
• ECG: Heart failure
• Ultrasound, CT scan: Haematoma, tumour, abdominal or pelvic mass
• Duplex Doppler, venography: Deep vein thrombosis, arteriovenous fistula
• Lymphangiography: Demonstrate cause of lymphoedema and whether due to hypoplasia or obstruction
• Lymph node biopsy: Infection, tumour
• Other investigations may include renal biopsy, echocardiogram

Management

Management is directed at identification and treatment of the underlying cause.