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🦵 Leg swelling
One leg or two? Unilateral is usually the leg; bilateral is usually the heart, the kidneys, the liver or the drug chart. And a hot swollen leg is not automatically cellulitis. Swelling of the FACE, NECK or ARM is a different problem — consider SVCO (search it) and go to that page rather than working through this card.
| Necrotising fasciitis Must exclude | Pain out of all proportion to the appearance, rapid spread over hours, systemic toxicity, bruising or crepitus. Early on the skin can look almost normal.A surgical call, not an antibiotic decision. Plastics or general surgery and critical care now. |
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| Compartment syndrome Must exclude | Pain out of proportion, worse on PASSIVE STRETCH of the compartment, with a tense swollen limb. Pulses are present until very late — their presence excludes nothing.Remove the cast or dressing, keep the limb at heart level, and call orthopaedics. Fasciotomy is time-critical. |
| Acute limb ischaemia Must exclude | The 6 Ps — pain, pallor, pulselessness, perishing cold, paraesthesia, paralysis. Swelling is late and suggests established damage.Vascular surgery immediately. Paraesthesia or paralysis means the limb is threatened now. |
| DVT Time-sensitive | Unilateral calf swelling, tenderness along the deep veins, warmth and pitting. A massively swollen, painful, blue leg is phlegmasia and is limb-threatening.Follow the Wells and NICE diagnostic pathway. D-dimer specificity is poor in inpatients and after surgery or with malignancy, so it should not overrule a high pre-test probability — image instead of repeating it. |
| Cellulitis / necrotising fasciitis Time-sensitive | Unilateral, hot, red, tender, with a spreading demarcated edge, usually with fever. Bilateral lower leg "cellulitis" is uncommon — venous eczema or lymphoedema is the likelier explanation.Mark the edge with a pen and the time. Antibiotics and elevate. If the pain is out of proportion, call a surgeon instead. |
| Acute pulmonary oedema Time-sensitive | Bilateral pitting oedema up to the thighs or sacrum, with orthopnoea, raised JVP and crackles. Sacral oedema in anyone who has been in bed.Diurese and look for the precipitant. Weigh them daily — it beats looking at the ankles. |
| Ruptured Baker's cyst Time-sensitive | Sudden calf pain and swelling with a history of knee arthritis, sometimes with bruising around the ankle. Clinically indistinguishable from DVT.Ultrasound — and it is ordered to exclude DVT, not to confirm the cyst. Never diagnosed clinically. |
| Drug-induced oedema Common | Bilateral ankle oedema on amlodipine or another dihydropyridine, NSAIDs, pioglitazone, gabapentinoids or steroids. Worse by evening, better overnight.Read the drug chart before starting a diuretic. Calcium-channel oedema is usually poorly responsive to loop diuretics — review the amlodipine rather than adding furosemide. |
| Hypoalbuminaemia Time-sensitive | Bilateral pitting oedema, sometimes with ascites and periorbital swelling. Liver disease, nephrotic syndrome, malnutrition, or a large inflammatory burden.Albumin, LFTs, and a urine protein:creatinine ratio. Nephrotic-range proteinuria needs a renal referral, not a diuretic alone. |
| AKI Time-sensitive | Oedema with oliguria and a rising creatinine, often after several days of fluid that nobody has totalled up.Look at the fluid balance chart and the weight. Fluid overload in AKI is a reason to stop giving fluid, not a reason to give more. |
| Pre-eclampsia Time-sensitive | New oedema after 20 weeks with hypertension and proteinuria. Facial and hand swelling matters more than ankle swelling, which is near-universal in pregnancy.Blood pressure, urine dip and bloods. Obstetric referral the same day. |
| Lymphoedema Common | Chronic, non-pitting late on, with skin thickening and a positive Stemmer sign — you cannot pinch the skin at the base of the second toe. After pelvic surgery, radiotherapy or recurrent cellulitis.Compression and skin care, with lymphoedema services. Diuretics do not work and cellulitis is the complication to prevent. |
| Venous insufficiency Common | Bilateral, worse by evening, with haemosiderin staining, varicose veins and gaiter-area skin changes. Frequently misdiagnosed as bilateral cellulitis and given repeated antibiotics.Assess arterial supply before significant compression — follow the local ABPI and vascular pathway. |
| Immobility / dependent oedema Common | Bilateral, in someone sitting in a chair all day or on a long-haul flight. Resolves overnight with the legs up.Elevation and movement. A reasonable explanation in a well patient with a normal JVP and normal bloods. |
14 differentials · 8 open a full pathway in the app.