What Are Hyperplastic Polyps

Colon polyps are outgrowths of the colon or rectum wall. Hyperplastic polyps are a subgroup of colon polyps. Most hyperplastic polyps are harmless, but there is a small risk of them becoming cancerous. They are usually discovered during a colonoscopy. Early detection and removal of precancerous polyps is important to reduce the risk of colon cancer. 

What are colon polyps?

The colon is a cylindrical tube through which food passes. The colon’s main function is to remove water and electrolytes and form a solid stool before it is excreted. The colon is lined by layers of cells that carry out these functions. These cells are maintained in a delicate balance between growth and death. In some cases, these cells grow excessively and form a tissue mass (a polyp). It is not always known why polyps grow, but there are certain risk factors. They can be found in different parts of the colon.

Colon polyps come in different shapes. They can be dome-shaped (sessile), they can be flat, or they can grow with a stalk, like a mushroom (pedunculated). They vary in size and can range from a few millimetres to a few centimetres in diameter. There are many different types of colon polyps, but this article will focus on hyperplastic polyps, which account for up to 30% of all colon polyps.1 The other main type of polyps are adenomas; these are generally larger and more likely to become cancerous than hyperplastic polyps.

Hyperplastic polyps

Hyperplastic polyps are a subgroup of the serrated (sawtooth-shaped) polyps. They are usually small (≤ 5 mm), usually found in the lower colon and rectum and are usually benign (non-cancerous).¹  However, they are more likely to turn cancerous if they are larger, towards the upper colon or have precancerous cells.¹

Symptoms

Colon polyps are usually asymptomatic but may present with the following symptoms if they are large or ulcerate and bleed:

• Abdominal pain
• A change in bowel habit–prolonged constipation or diarrhoea
• Nausea
• Passing blood or mucus in your poop
• Tiredness
• Unexplained weight loss

Many of these symptoms are also associated with other conditions, and a diagnosis should be made by a trained medical professional. For more information about any worrying symptoms, please visit the NHS website or speak to your local GP.²

Diagnosis 

Colon polyps are most commonly detected during a colonoscopy when the doctor is looking for something else like inflammatory bowel disease or colon cancer. Your doctor may order a colonoscopy if they think your symptoms indicate the presence of colon polyps or colon cancer. 

A colonoscopy involves inserting a long, thin tube with a camera on it into your bottom to take a close look at the bowel wall. This procedure may be uncomfortable but should not be painful. Alternatively, a CT colonography test may be performed. This involves taking X-rays of your colon to detect any polyps. The doctor will often take a sample (biopsy) of the polyp to determine its type and look for any signs of cancer.

Potential complications

There are two potential complications that can occur with colon polyps:

1. The colon polyp could block or impair the passage of food if it is large enough. In serious cases, this could lead to an obstruction in the colon, which would require a surgical procedure to remove it.
2.  A colon polyp could be cancerous. Generally, the larger the polyp, the greater the chance of it becoming cancerous. It often takes a long time for a colon polyp to turn cancerous.

It is often difficult to distinguish between a cancerous polyp and a non-cancerous polyp from a colonoscopy, so a doctor may take a sample (biopsy) to look at the cells in more detail under a microscope.

A doctor will be able to determine the type of polyp from a biopsy sample and distinguish whether it is hyperplastic or another type. Some colon polyps contain pre-cancerous cells so it is important that they are investigated quickly and if necessary, removed before they can develop into a cancer tumour.

It is perfectly understandable to be worried if you are waiting for the results of a colon biopsy, but early detection reduces the risk of the cancer developing.

Treatments

This will depend on the patient and the type and size of the colon polyp. Bowel polyps are removed surgically in a procedure called a polypectomy. During the procedure, a colonoscope camera will be used to locate the polyp. The polyp will be removed with a wire loop (snare) that encircles the polyp, and the tissue is burnt off (cauterised).³ 

There are different techniques for removing the polyp. Treatments will depend on the probability of the polyp turning into cancer and the risk of bleeding during surgery.⁴ It may also be necessary to remove a large polyp if it is likely to obstruct the colon. A follow-up appointment is often necessary to screen for the return of colon polyps or the development of polyps into colon cancer tumours.

Risk factors

Lifestyle factors

Certain lifestyle factors increase the probability of developing polyps:

• Alcohol – Drinking large amounts of alcohol has been found to increase the probability of developing polyps⁵
• Smoking – Regular smokers are also at an increased risk of developing colon polyps⁵
• Diet – Consumption of a high-fat diet and red meat is associated with an increase in colon polyps⁵
• Being overweight – people with a higher BMI are more likely to have colon polyps⁵

A balanced diet rich in fibre and nutrients is recommended to maintain a healthy gut and reduce the risk of developing colon polyps or colon cancer. Consumption of sugary and fatty foods and red meat should be reduced if necessary. It is recommended that alcohol should only be drunk in moderation (within the recommended levels), and smokers are recommended to quit if possible. Regular exercise is also beneficial not only for a healthy gut but for all the organ systems of the body.

Non-modifiable factors

There are also a few non-modifiable factors that increase the risk of getting colon polyps.

Age

With increasing age comes an increased risk of colon polyps. Colon polyps are quite common in older people. Around 25% of people over the age of 50 will have at least one colon polyp.²

Previous history of colon polyps

People who have had one or more polyps are more likely to develop further polyps in the future.

Associated conditions

Inflammation in the colon can be a trigger for the development of colon polyps. Inflammatory bowel diseases like ulcerative colitis and Crohn’s disease provide a long-term inflammatory environment, which can lead to polyp formation. People with these conditions are more likely to have colon polyps.⁶

Inherited genetic mutations in certain conditions can also predispose people to colon polyps:

Familial adenomatous polyposis (FAP) 

People with FAP inherit a mutation in a gene (APC) which causes excessive growth of cells in the colon wall, leading to the development of multiple colon polyps. Unfortunately, people with this mutation also have an increased risk of colon cancer.

MUTYH-associated polyposis

This is caused by a genetic mutation in the MUTYH gene and is also associated with multiple colon polyp formation.

If other people in your family have had colon polyps or colon cancer, you are more likely to have them. Genetic testing may be recommended in families with a strong history of colon polyps or colon cancer. People with multiple polyps, especially younger people, maybe offered genetic testing to screen for some of the conditions listed above.

Summary

Colon polyps are outgrowths of the colon wall. They are normally asymptomatic, but you may have symptoms if they are larger. The most common symptoms are abdominal pain, a change in bowel habits, or blood in your poop. If you have worrying symptoms, it is recommended that you speak to your local GP.

This article focused on a subgroup of colon polyps, hyperplastic polyps. These are generally small and non-cancerous, but in rare cases, they can turn into cancer. Colon polyps are usually diagnosed during a colonoscopy. The doctor may decide to take a biopsy sample to investigate the type of polyp and to look for cancer.  Colon polyps are often removed surgically, and it may be necessary to have a follow-up appointment to check that the polyps haven’t regrown or turned cancerous.

There are certain risk factors for colon polyps; these include smoking regularly, drinking large amounts of alcohol, consumption of a high-fat diet, and a high BMI. Eating a healthy diet and reducing smoking and alcohol consumption will reduce your risk of developing colon polyps and colon cancer. Colon polyps are relatively common in older people, and if you have had one or more polyps previously, you are more likely to have more in the future. People with inflammatory bowel disease have more colon polyps. Some rare inherited conditions increase your risk of developing colon polyps. These include Familial Adenomatous Polyposis (FAP) and MUTYH-associated polyposis. It may be necessary to do genetic screening for these conditions in some people.