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Hemorrhoids are swollen blood vessels around your anus and inside your rectum.

We don't know exactly what causes hemorrhoids, but experts think they occur when the small blood vessels (veins) in the lining of your rectum become wider and swollen with blood.¹

Here are some reasons why you may get hemorrhoids.

• You strain when you go to the bathroom, perhaps because you're constipated. You may not be eating enough fiber.
• If you are a woman and you're pregnant. Pressure from your baby may restrict the flow of blood around your anus. And changes in your hormones may affect your veins.
• You may also be more likely to get hemorrhoids if the walls of your veins are weak. You can inherit this from your parents in your genes.

You can get hemorrhoids either inside your rectum, or outside, under the skin around your anus.² Your anus is the opening from your rectum.

Doctors put hemorrhoids into four categories, depending on how bad they are.³

• First degree: These are small swellings on the inside of your rectum. You can't see them or feel them from outside. They may bleed when you go to the bathroom, but your symptoms are mild.
• Second degree: These are larger swellings. They may partly push out (prolapse) from your anus when you go to the bathroom. But they soon spring back inside again.
• Third degree: The swellings hang out from your anus. You can push them back inside with your finger.
• Fourth degree: The swellings become quite large. They are permanently outside your anus. You can't push them back inside.

To diagnose hemorrhoids, your doctor will need to do a physical exam. They will look for swollen blood vessels around your anus. Your doctor may use an anoscope (a hollow tube with a light) to look for hemorrhoids inside your rectum.

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.