Dilated veins, similar to varicose veins, that are found in the anal canal (internal hemorrhoids), or at the anal opening (external hemorrhoids). They are often chronic and become a problem when they bleed, become painful, develop a blood clot or enlarge. Hemorrhoids may be more likely to develop if you have been pregnant or tend to sit for prolonged periods, or have constipation, liver disease (cirrhosis), or infections of the anal canal. In general, internal hemorrhoids bleed but are not painful. External hemorrhoids are painful but usually do not bleed as much as internal hemorrhoids.