How can haemorroids form in rectum area and what causes them to bleed?

Pressure and trauma. Hemorrhoids are enlarged veins that exist under the lining of the rectum and anus. The primary cause of hemorrhoids is increased abdominal pressure, from chronic constipation, prolonged sitting, pregnancy and in some cases, from other diseases, such as liver disease. They are usually fleshy and soft but cause discomfort when engorged and bleed with trauma such as passing hard stool or hard wiping.