haemorrhoids Varicose veins in the anal canal. Haemorrhoids may involve the veins near the upper end of the canal, causing internal piles, or those at the lower end, just under the skin, causing external haemorrhoids. Both may be affected. They cause bleeding, pain and a sense of incompleteness when defaecating. Internal piles may pass out of the anus (prolapse). Treatments include direct surgical excision (haemorrhoidectomy), injection (sclerotherapy), laser coagulation, infra-red coagulation, radiofrequency coagulation, or rubber band encirclage. From the Greek haimorrhoia , a flow of blood.