Sudden swelling and tenderness in one leg needs prompt care; added sudden breathlessness or chest pain means call 120
A suddenly enlarged, tight, tender leg needs prompt venous ultrasound assessment. If sudden breathlessness, pain on deep inspiration, rapid heartbeat or dizziness follows, a clot may have reached the lungs: call China's 120. Confirmed pulmonary-embolism patients in one registry had 17.4% three-month mortality. Travel immobility beyond 4 hours roughly doubled clot risk, though individual absolute risk stayed low.
What it takes
Lower-limb venous ultrasound costs around RMB 100–200 in the Chinese estimate.
What you may gain
ICOPER included 2,454 confirmed acute pulmonary-embolism patients from 52 hospitals in 7 countries. Pulmonary embolism means a clot obstructing the pulmonary arteries. Three-month all-cause mortality was 17.4% (426/2454). WHO's WRIGHT project found that travel lasting over 4 continuous hours approximately doubled venous-thromboembolism risk, but the absolute risk after over 4 hours of immobility remained about 1 in 6,000.
Context & considerations
Both legs swelling more often suggests heart, liver, kidney or venous-function problems; sudden one-sided enlargement is a typical deep-vein-thrombosis pattern. Risks include long journeys, bed rest after surgery/fracture, casts, pregnancy and childbirth, cancer and oral contraceptives. A detached clot reaching the pulmonary artery can cause sudden breathlessness, pain worse on inspiration, rapid heartbeat, dizziness or coughing blood: call 120. The 17.4% figure concerns confirmed pulmonary embolism, not everyone with a swollen leg.
Research & references
Goldhaber SZ, Visani L, De Rosa M (1999). Acute pulmonary embolism: clinical outcomes in the International Cooperative Pulmonary Embolism Registry (ICOPER). Lancet, 353(9162), 1386-1389. https://doi.org/10.1016/S0140-6736(98)07534-5; WHO (2007). Study results released on travel and blood clots. https://www.who.int/news/item/29-06-2007-study-results-released-on-travel-and-blood-clots