Silent Threat: Brazil Grapples with Rising Thrombosis Cases and Prevention

Blood clots form silently. A person goes about their day—exercising, working, living—and then something shifts. A leg darkens. Pain arrives without warning. By the time you notice, the danger is already inside you.

This is thrombosis, and it is far more common than most Brazilians realize. Between January 2012 and August 2023, the Brazilian Society of Angiology and Vascular Surgery documented over 489,000 hospitalizations for venous thrombosis alone. That is more than a decade of people arriving at emergency rooms with clots blocking blood flow through their veins, facing the possibility of pulmonary embolism, stroke, or heart attack.

Sarah Femina was 21 years old and in the middle of filming a video when her left leg began to change. It darkened. It swelled. The pain was unlike anything she had experienced before. The influencer and actress, based in Araras in São Paulo state, sought medical help immediately and received a diagnosis that shook her: deep vein thrombosis in her femoral and iliac veins. She spent three days in the hospital and would need anticoagulant medication through June. "The worst pain I've ever felt in my life," she said in an interview. "I've never had anything wrong with me before. I'm very active. It's strange because I'm young, I exercise." She had been terrified of losing her leg.

What makes thrombosis particularly dangerous is that it does not announce itself. The condition develops when blood coagulates inside a vein or artery, forming a semi-solid mass that blocks circulation. It can happen to anyone, but certain circumstances make it far more likely: recent surgery, long periods of immobility, use of estrogen-based birth control or hormone replacement therapy. Cardiologist Agnaldo Píscopo explained that inflammatory diseases dramatically increase risk. COVID-19 is pro-thrombotic, elevating the chances substantially. Cancer does so even more dramatically. The virus or illness itself becomes a catalyst for the body to form clots.

Diagnosis requires a careful approach. Doctors begin with a patient's history, mapping out risk factors. They perform a physical examination of the affected area and measure D-dimer, a key marker for detecting clots. Doppler ultrasound—a non-invasive imaging method—evaluates blood flow in the veins, particularly in the legs. In specific cases, phlebography uses contrast dye to visualize veins through X-ray. CT scans with thrombosis protocol are used mainly when pulmonary embolism is suspected, though they help in other situations too.

Treatment aims to stop the clot from growing and prevent complications. Anticoagulants are the standard approach—medications that prevent new clots from forming and stabilize existing ones. In more severe cases, thrombolytics dissolve clots directly within the vein under hospital supervision. When anticoagulants cannot be used, doctors may insert a vena cava filter to prevent clots from reaching the lungs.

Prevention is simpler than treatment, though it requires discipline. Movement matters enormously—staying still for long periods, especially during travel or hospitalization, allows clots to form. Regular physical activity improves blood flow. Drinking water regularly reduces blood viscosity. Smoking damages blood vessels and must be avoided. An angiologist is the specialist to consult with thrombosis concerns, as they focus specifically on vascular problems. But if thrombosis is suspected, emergency care should not wait. The window between symptom and serious complication can be narrow, and speed matters.