血栓

1. Origins, structure, and basic meaning

• Structure: 血栓 (けっせん) is a medical noun for a clot formed when blood coagulates within a vessel.
• Basic usage: 血栓の有無を調べる makes presence or absence the subject of a test, while 血栓ができる危険 modifies the risk of formation during prolonged immobility.

2. Common pitfalls and similar expressions

• Existing clot and formation risk
  • 血栓の有無 checks current presence, whereas 血栓ができる危険 concerns future possibility. Elevated risk alone does not establish that a clot already exists.