Hyytymä

Hyytymä, also known as a thrombus in medical terminology, is a solid mass formed by platelets, fibrin, and trapped blood cells that adheres to the lining of a blood vessel. It develops during abnormal hemostasis and can impede or completely block blood flow. A hyytymä is typically attached to the vessel wall; if it detaches and travels through the circulation it is called an embolus and may cause distant blockage, such as in the lungs or brain.

Thrombi form when endothelial injury, slow or turbulent blood flow, and an underlying tendency to clot (hypercoagulability) overlap — Virchow's triad. Arterial thrombi are usually rich in platelets and form in the arteries, often in association with atherosclerosis. Venous thrombi are typically rich in fibrin and red blood cells and form in veins, commonly in the legs (deep vein thrombosis, DVT).

Clinical signs depend on location: DVT may cause leg swelling and pain; pulmonary embolism may cause sudden shortness of breath, chest pain, or fainting; arterial thrombi can cause organ ischemia such as stroke or myocardial infarction.

Diagnosis relies on combining history with tests and imaging. D-dimer testing is sensitive but not specific; compression ultrasound is used for suspected DVT; CT or MR angiography is used for pulmonary embolism or arterial occlusion.

Treatment aims to prevent propagation and relieve occlusion. Anticoagulant medicines (for example heparin, direct oral anticoagulants, or warfarin) are commonly used. In selected cases, thrombolysis or mechanical thrombectomy, vascular surgery, or filter devices may be indicated. Prevention includes risk factor modification and, in hospital settings, mechanical or chemical prophylaxis.