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Swelling in One Leg Only
One of the most telling signs of a deep vein thrombosis (DVT) — a blood clot in a deep vein — is sudden swelling in just one leg. Unlike general fluid retention that affects both legs, a DVT typically causes one calf or thigh to become noticeably larger than the other. The swelling may develop quickly over hours and the affected leg may feel heavy and tight. This is a medical emergency because the clot can break free and travel to your lungs.