The doctor found that a blood clot was occluding the patient's vein.

occluding 是动词 occlude 的现在分词形式。occlude 来自拉丁语词根 occludere，由 ob-（表示"阻挡"）和 claudere（"关闭"）组成，意思是"阻塞、封闭"。在医学语境中特指血管或管道的堵塞。