The silent traveler: how a leg clot can block your lungs

Science · Published 24 October 2026 Swipe more like this →

In short: A blood clot doesn't always stay where it starts. Often, a clot forming in the deep veins of your leg can break loose, travel through your bloodstream, and lodge itself in your lung arteries, creating a life-threatening blockage known as a pulmonary embolism.

A pulmonary embolism (PE) is a critical condition where an embolus—a dislodged blood clot—obstructs blood flow to the lungs. While these clots frequently originate from deep vein thrombosis (DVT) in the legs, they can also develop directly within the small blood vessels of the lungs. The onset of symptoms can be unpredictable; some individuals experience no symptoms at all, while others face sudden respiratory distress within seconds or minutes. In other cases, symptoms may develop gradually over days or weeks.

Recognizing the clinical signs is vital for prompt management. Common indicators include sudden shortness of breath, chest pain that intensifies during deep breathing, and a rapid heart rate. Less frequent symptoms include coughing up blood, lightheadedness, or sweating (S2:<0xE2><0x80><0x8A>p2, S4:p3). Because the condition can be life-threatening, medical professionals use various diagnostic tools. The primary diagnostic method is Computed Tomography Pulmonary Angiography (CTPA), which uses imaging to locate clots in the lung vessels. Doctors may also use D-dimer blood tests to detect substances released when clots dissolve, or V/Q scans to measure air and blood flow.

Treatment focuses on preventing the clot from expanding and stopping new ones from forming, typically through anticoagulants. In a hospital setting, patients might receive anticoagulant injections, followed by a period of at least five days of injections and at least three months of oral tablets. While the condition is serious, early detection and treatment can lead to a full recovery. Risk can be mitigated during long journeys, such as flights exceeding four hours, by staying hydrated, wearing flight socks, and moving the legs frequently.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?

Related

• Why the biggest lung clots are often the ones that don't hurt
• An embolism is a traveling blockage that can strike anywhere in your body
• Thrombosis is the silent blockage of your circulatory system by internal blood clots
• Genes explain about half the variation in who develops dangerous vein clots
• When Seconds Count: The High-Stakes Management of Pulmonary Embolism
• Mapping the hidden arterial network of the human pelvis
• How complex shapes emerge from simple, rotating circles
• Does your body feel the fear first, or does your mind?
• Can you solve a complex math problem in just three seconds?
• Your behavior might be driven by memories you don't even know exist
• How do extreme breath-holders push the boundaries of human physiological limits?
• The human mind is less like a vessel and more like a processor

More in Science · Latest · A–Z · All topics