Colorectal polyps develop over years and for most of that time cause no symptoms at all. They are usually found during a colonoscopy performed for another reason. Below we describe what they are, what types exist, how they are diagnosed and when a doctor decides to remove them.
What are colorectal polyps
Polyps are abnormal growths arising from the mucosa, the inner layer of the bowel wall, and protruding into its lumen. They occur in 15–40% of adults and more often in men.
They may appear singly or in larger numbers, a condition known as polyposis. Most polyps are benign, but some types carry a risk of turning into colorectal cancer.
Types of polyps
Polyps fall into two main categories: non-neoplastic and neoplastic.
Non-neoplastic polyps
These include hyperplastic (also called serrated), hamartomatous and pseudopolyps. Hyperplastic polyps occur most often in the final section of the large bowel — the rectum and sigmoid colon.
Adenomatous polyps
This is the most common type in adults. By structure they are divided into tubular, villous, tubulovillous and serrated. They are characterised by dysplasia of the glandular epithelium, of low or high grade. The likelihood of a polyp turning into cancer depends on its size, appearance and tissue structure.
Risk factors
The causes of polyps are not fully understood. Diet, lifestyle and chronic bowel inflammation are considered to play a role, as is inherited predisposition. The risk factors listed include:
- overweight and obesity
- too little fibre in the diet
- a sedentary lifestyle
- a diet rich in red meat
- irritable bowel syndrome
- smoking
- drinking alcohol
The risk increases with age, markedly after the age of 30.
What symptoms polyps cause
Polyps most often cause no symptoms at all, especially when smaller than 1 cm. Complaints usually appear with larger lesions or with polyposis. The following are listed:
- bleeding from the polyp
- mucus in the stool
- urgency to defecate
- watery diarrhoea
- pain in the lower abdomen
- a feeling of incomplete evacuation
- a change in bowel rhythm
- unexplained weight loss
None of these symptoms is specific to polyps — each of them requires medical assessment.
Diagnosis
Diagnosis relies on endoscopic and imaging examinations that detect lesions, assess their size and character and, if needed, remove them during the same procedure. In practice these are:
- the faecal occult blood test (FIT/FOBT) — detects blood invisible to the naked eye
- colonoscopy — allows the inside of the bowel to be viewed, polyps removed and samples taken for examination
- sigmoidoscopy — an endoscopic examination of the lower large bowel, performed as an initial test or an alternative
The scope of diagnosis is decided by the doctor after the interview and examination.
Polypectomy and follow-up
Removing a polyp is called a polypectomy. It is most often performed during the colonoscopy itself, using a snare or forceps passed through the endoscope. With a large number of lesions several procedures may be needed, and lesions in the rectum are also removed using a rectoscope.
Larger polyps and more complex cases may require surgery. The doctor decides how to proceed after assessing the lesion.
Every removed polyp is sent for histopathological examination. After the procedure the doctor sets a date for a follow-up colonoscopy — usually every 2–3 years.
This content is educational and does not replace medical advice. It is not intended for diagnosing or treating illness on your own. If you have worrying symptoms, contact a doctor.
