If these valves are weak or broken, blood can flow backward and pool from the veins, triggering the veins to stretch or twist. Blood can pool within an exterior hemorrhoid and sort a clot, identified as a thrombus. A thrombosed hemorrhoid may lead to: 初级医疗护理专业人员可能建议您去看专门诊治静脉状况的医生（即静脉科医生或血管外科医生）或治疗皮肤状况的医生（即皮肤科医生或皮肤外科医生... https://www.sgvascularctr.com/varicose-vein-treatment-in-singapore-answers-to-your-most-common-questions/