Haemorrhoids (piles) are swellings that develop from the lining of the anus and lower rectum (back passage). Symptoms range from temporary and mild, to persistent and painful.

Causes, incidence, and risk factors

There is a network of small veins (blood vessels) within the inside lining of the anus and lower rectum. These veins sometimes become wider and engorged with more blood than usual. These engorged veins and the overlying tissue may then form into one or more small swellings called haemorrhoids.

The exact reason why these changes occur and lead to haemorrhoids forming is not clear. Some haemorrhoids seem to develop for no apparent reason. However, it is thought that the pressure in and around the anus can be a major factor in many cases. If the pressure in and around the anus is increased, then it is thought that this can lead to haemorrhoids developing.

Certain situations increase the chance of haemorrhoids developing:

• Constipation, passing large stools (faeces), and straining at the toilet. These increase the pressure in and around the veins in the anus and seem to be a common reason for haemorrhoids to develop.
• Pregnancy. Haemorrhoids are common during pregnancy. This is probably due to pressure effects of the baby lying above the rectum and anus, and the affect that the change in hormones during pregnancy can have on the veins.
• Ageing. The tissues in the lining of the anus may become less supportive as we get older.
• Hereditary factors. Some people may inherit a weakness of the wall of the veins in the anal region.

Symptoms

Internal haemorrhoids

These form in the back passage about 2-4 cm above the rim (opening) of the anus. Their severity and size are classified into grades 1 to 4:

• • • Grade 1 are small swellings on the inside lining of the back passage. They cannot be seen or felt from outside the anus. Grade 1 haemorrhoids are common. In some people they enlarge further to grade 2 or more.
    • Grade 2 are larger. They may be partly pushed out (prolapse) from the anus when you go to the toilet, but quickly spring back inside again.
    • Grade 3 hang out (prolapse) from the anus. You may feel one or more as small, soft lumps that hang from the anus. However, you can push them back inside the anus with a finger.
    • Grade 4 permanently hang down from within the anus, and you cannot push them back inside. They sometimes become quite large.

  Symptoms can vary. Small haemorrhoids are usually painless. The most common symptom is bleeding after going to the toilet. Larger haemorrhoids may cause a mucous discharge, some pain, irritation, and itch. The discharge may irritate the skin around the anus. You may have a sense of fullness in the anus, or a feeling of not fully emptying your rectum when you go to the toilet.

A possible complication of haemorrhoids that hang down (grade 3-4) is a blood clot (thrombosis) which can form within the haemorrhoid. This is uncommon, but causes intense pain if it occurs.

External haemorrhoid (sometimes called a perianal haematoma)

This is less common than internal haemorrhoids. An external haemorrhoid is a small lump that develops on the outside edge of the anus. Many do not cause symptoms. However, if a blood clot forms in the haemorrhoid (a thrombosed external haemorrhoid) it can suddenly become very painful and need urgent treatment. The pain due to a thrombosed external haemorrhoid usually peaks after 48-72 hours, and then gradually goes away over 7-10 days. A thrombosed external haemorrhoid may bleed a little for a few days. It then gradually shrinks to become a small skin-tag.

Some people develop internal and external haemorrhoids at the same time.