What causes swelling in the feet?
Foot swelling, or pedal edema, refers to the accumulation of excess fluid in the tissues of the feet and ankles. It can result from a wide range of underlying causes—some benign and transient, others indicative of serious systemic disease. Common non-urgent contributors include prolonged standing or sitting, venous insufficiency (where incompetent valves in leg veins impair blood return to the heart), mild trauma, or localized infection. Certain medications—such as calcium channel blockers (e.g., amlodipine), NSAIDs, corticosteroids, and some diabetes medications like thiazolidinediones—can also promote fluid retention.
More concerning etiologies involve cardiac, renal, hepatic, or lymphatic dysfunction. For example, congestive heart failure may reduce cardiac output and elevate venous pressure, leading to fluid transudation into interstitial spaces—often first apparent in dependent areas like the feet. Nephrotic syndrome or chronic kidney disease can cause hypoalbuminemia and sodium retention, while cirrhosis contributes via portal hypertension, reduced albumin synthesis, and secondary hyperaldosteronism. Lymphedema—whether primary (congenital) or secondary (e.g., post-surgical or radiation-related)—results from impaired lymphatic drainage and typically presents with non-pitting, firm swelling that may progress proximally.
Other important considerations include deep vein thrombosis (DVT), which often causes unilateral, painful swelling with warmth and erythema; cellulitis, characterized by acute onset, fever, and tenderness; and systemic conditions such as hypothyroidism or autoimmune disorders like lupus or sarcoidosis. A thorough clinical evaluation—including history (onset, laterality, associated symptoms), physical exam (pitting vs. non-pitting, symmetry, skin changes), and targeted investigations (e.g., BNP, renal function tests, liver enzymes, duplex ultrasound, or echocardiography)—is essential to determine the root cause and guide appropriate management.