Virtual chromoendoscopy to assess colorectal polyps during colonoscopy

Colorectal polyps are common, affecting 15% to 20% of the UK population. Most polyps produce no symptoms, but some larger polyps can cause a small amount of rectal bleeding, diarrhoea, constipation or abdominal pain.

Colorectal cancer is one of the most common cancers in the UK and is the second most common cause of cancer death. About 40,000 new cases are registered each year. Colorectal cancer is strongly related to age, with almost three‑quarters of cases occurring in people aged 65 or over.

Colonoscopy examinations may be done for several clinical reasons, including:

• further investigation of symptoms suggestive of colorectal cancer

• further investigation of a positive faecal occult blood test as part of the NHS bowel cancer screening programme or

• ongoing checks (surveillance) after removal of adenomatous polyps.

The NICE guideline on suspected cancer recommends that people should be referred for colorectal cancer investigations within 2 weeks if:

• they are aged 40 and over with unexplained weight loss and abdominal pain or

• they are aged 50 and over with unexplained rectal bleeding or

• they are aged 60 and over with iron-deficiency anaemia or changes in their bowel habit or

• tests show occult blood in their faeces.

The guideline also recommends that people should be considered for referral for colorectal cancer investigations if:

• they have a rectal or abdominal mass

• they are aged under 50 with rectal bleeding and have any of the following unexplained symptoms or findings:

  • abdominal pain

  • changes in bowel habit

  • weight loss or

  • iron deficiency anaemia.

The NHS bowel cancer screening programme offers screening every 2 years to men and women aged 60 to 74. The screening programme invites eligible adults to have a faecal occult blood test. This involves collecting 3 stool samples and posting them to the laboratory to be checked for the presence of blood, which could be an early sign of colorectal cancer. People with an abnormal faecal occult blood test result are offered a colonoscopy.

The NICE guideline on colonoscopic surveillance recommends that colonoscopies are offered to people:

• with inflammatory bowel disease whose symptoms started 10 years ago or

• who have had adenomas removed and are at intermediate or high risk of developing colorectal cancer.
  
  It also recommends that colonoscopic surveillance is considered for people who have had adenomas removed and are at low risk of developing colorectal cancer. The frequency of surveillance may be every 1, 3 or 5 years, depending on the level of risk of developing colorectal cancer.

For investigating possible colorectal cancer in secondary care, the NICE guideline on colorectal cancer recommends that:

• people without major comorbidity are offered colonoscopy

• people with major comorbidity are offered flexible sigmoidoscopy plus barium enema

• CT colonography is considered as an alternative to colonoscopy or flexible sigmoidoscopy plus barium enema, if the local radiology service can show competency in this technique

• people who have had an incomplete colonoscopy are offered repeat colonoscopy, CT colonography (if the local radiology service can show competency in this technique), or a barium enema.

If colorectal polyps are found during a colonoscopy they can be removed using cauterisation or a snare (polypectomy). Polyps removed by polypectomy are sent for histopathology to determine whether they are hyperplastic or adenomatous.

If colorectal cancer is suspected, biopsies are taken and sent to the laboratory to determine whether the sample contains benign or malignant cells. If colorectal cancer is confirmed, the NICE guideline on colorectal cancer recommends further imaging tests, such as CT or MRI, to stage the cancer and determine what treatment is needed.

Colonoscopy is usually done as an outpatient procedure with the person having sedation or painkillers. People having colonoscopy may be concerned about the adverse effects of the colonoscopy, such as heavy bleeding or perforation of the bowel. Colonoscopy with polypectomy also has an increased risk of bleeding and perforation compared with colonoscopy without polypectomy. Some people may also have a reaction to the sedative which could result in temporary breathing or heart problems.

If colorectal cancer is not diagnosed then surveillance colonoscopy is offered, and the length of time between assessments depends on the risk of cancer. The NICE guideline on colonoscopic surveillance recommends that people with:

• 1 or 2 small (less than 10 mm) adenomas are at low risk, and need either no, or 5‑yearly, colonoscopic surveillance until they have 1 negative examination, after which surveillance stops

• 3 or 4 small adenomas of less than 10 mm or at least 1 adenoma that is 10 mm or more are at intermediate risk and should be screened 3‑yearly until they have 2 consecutive negative examinations

• 5 or more adenomas smaller than 10 mm, or 3 or more adenomas at least one of which is 10 mm or more, are at high risk and should have an extra examination at 12 months before returning to 3‑yearly surveillance.

If colorectal cancer is diagnosed, it may be treated with surgery, chemotherapy or radiotherapy, or sometimes with biological agents such as cetuximab. Treatment depends on the stage of the cancer and is described in more detail in the NICE guideline on colorectal cancer.