A patient with red, warm, swollen lower legs — both of them — is very unlikely to have bilateral cellulitis. Cellulitis is nearly always unilateral, because it follows a breach in one limb's skin barrier.
What bilateral redness usually is: venous stasis dermatitis, lipodermatosclerosis, or the erythema of chronic oedema from heart failure, nephrotic syndrome or venous insufficiency. These are itchy more often than painful, chronic rather than acute, and they do not come with fever or a rising white cell count. Patients with them are frequently admitted, given a week of intravenous antibiotics, discharged unchanged, and readmitted.
So when both legs are involved, ask about the time course before reaching for an antibiotic. Acute onset over hours to a day, unilateral, painful, with systemic upset points to infection. Weeks of gradually worsening bilateral change, itch rather than pain, with skin thickening and haemosiderin staining, points to venous disease — and the treatment is compression and emollient, not flucloxacillin.
- Ask whether one leg or both, and over what time course, before prescribing
- Itch rather than pain points away from infection
- Look for haemosiderin staining and skin thickening — signs of a chronic process
- Check for the systemic features: fever, tachycardia, rising inflammatory markers
- Where the diagnosis is venous, start compression rather than a second antibiotic course
Why it matters
Bilateral venous change treated as infection is one of the commonest avoidable antibiotic courses in general medicine.
Read the rest in the app
You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.
Scan to keep reading on your phone. No account needed to start.
Tomorrow morning, before your first patient
One edition a day for top clinical updates, written by the desk, every claim tied to its paper. Six minutes.
Get the app — free