Heat Oedema

Heat oedema is mild, painless, dependent swelling of the feet, ankles and sometimes hands in the first days to weeks of heat exposure in unacclimatised people. It is benign and self-limited.

Epidemiology. Common in travellers, new workers and older adults, especially women and those standing or sitting for long periods.

Course. It resolves over days to about 2 weeks with acclimatisation and needs no specific treatment.

Pathophysiology.

Heat causes cutaneous vasodilation with pooling of blood and fluid in dependent areas. Increased aldosterone and antidiuretic hormone activity during acclimatisation retains salt and water.

• Bilateral pitting swelling of the feet and ankles, sometimes the hands, with no pain.
• Normal vital signs, no systemic features and no skin change.

Red flags.

• Unilateral leg swelling, calf pain or tenderness (deep vein thrombosis).
• Dyspnoea, orthopnoea, rapid weight gain or chest pain (heart failure).
• Facial puffiness, hypertension or proteinuria (renal disease, pre-eclampsia).

• Clinical diagnosis based on timing with heat exposure and absence of other findings.
• Examine heart, lungs, jugular venous pressure, abdomen and legs; check blood pressure.
• Urinalysis, creatinine, liver tests and albumin when swelling is persistent, marked, or the pattern is atypical. Natriuretic peptide and echocardiography when heart failure is suspected.
• Leg ultrasound for unilateral swelling.

Differential diagnosis. Heart failure, chronic venous insufficiency, deep vein thrombosis, nephrotic syndrome, liver disease, hypothyroidism, lymphoedema, drug induced oedema (calcium channel blockers, NSAIDs, corticosteroids, pioglitazone), pre-eclampsia.

• Reassure; elevate the legs, walk regularly and avoid prolonged sitting or standing.
• Light graduated compression stockings for work shifts.
• Continue drinking fluids and normal salt intake; do not restrict salt in the heat.
• Diuretics are not advised because they increase the risk of volume depletion, electrolyte loss and heat illness.
• Expect resolution with acclimatisation; reassess if swelling persists beyond 2 weeks.

Monitoring. Review at 1 to 2 weeks if swelling persists.

Referral and escalation. Investigate for another cause when swelling is persistent, asymmetric or accompanied by any red flag; occupational physician for workplace acclimatisation and rest arrangements.

Special groups. Pregnancy: check blood pressure and urine protein, because oedema may signal pre-eclampsia.