Colonoscopy

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What is Colonoscopy?

Illustration of Colonoscopy

Colonoscopy in Singapore is a procedure performed by gastroenterologists to check for any abnormalities in the lower gastrointestinal tract (colon & rectum) and to treat certain conditions. 

This is a day procedure and takes about 30 minutes to an hour, which means you’ll be able to go home on the same day, shortly after the colonoscopy is completed. It involves the insertion of a long, flexible tube with a light and camera at the end through the anus and is guided upwards into the rectum and colon. Any masses, tumours, inflammation or bleeding can be visualised easily, and biopsies (tissue samples) are sent for testing if needed. A colonoscopy can also be performed to remove small masses such as polyps, which could be precursors to colorectal cancer. 

“Colorectal cancer is the most common cancer amongst Singapore males and the second most common among Singapore females. However, it is a highly preventable cancer and screening colonoscopy is one such modality that can reduce your risk. If you are aged 50 and above (or younger if you have risk factors for colorectal cancer), please remember to ask your Gastroenterologist about colorectal cancer screening even though you may be seeing him/her for another problem,” advises Dr Benjamin Yip. 

Who needs a Colonoscopy?

Colonoscopies are routinely offered for normal adults aged 50 and above for screening and early detection of colorectal cancer or earlier for certain higher-risk groups, such as those with a family history of colorectal cancer. A colonoscopy procedure in Singapore may also be recommended by your gastroenterologist if you show symptoms suggestive of a more sinister problem, such as blood in your stools or iron deficiency anaemia. 

In screening colonoscopies for people with no symptoms, the main purpose is to check for any polyps (small growths) and to detect colorectal cancer in its early stages. If any polyps are found, they are removed and sent for testing to determine if they are pre-malignant or malignant (cancerous).

Colonoscopy: Diagnostic vs Therapeutic

Diagnostic

Diagnostic Colonoscopy

If you’re experiencing new symptoms related to your gut, such as abdominal pain, new diarrhoea or constipation, a change in the size of your stools, unexplained weight loss, or blood in your stools, your doctor may offer a diagnostic scope.

A diagnostic scope is done with the purpose of identifying the cause of your symptoms and diagnosing the disease (if any). Some conditions that are commonly diagnosed on colonoscopy include:

  • Colorectal polyps
  • Colorectal cancer
  • Crohn’s disease
  • Ulcerative colitis
  • Diverticular disease, etc.

Therapeutic

Therapeutic Colonoscopy

Therapeutic colonoscopy is used to perform minimally-invasive procedures in the colon or rectum, such as haemostasis (stopping bleeding), removal of abnormal masses, or foreign body extraction.

Patients with diverticular disease, known vascular malformations, or recurrently bleeding tumours may experience bleeding from the lower gastrointestinal tract that does not spontaneously stop. In such instances, endoscopic hemostasis may be offered, which in simple terms means that the endoscope is used to locate the site of bleeding, and heat is applied to the area to stop the bleeding.

For patients with ulcerative colitis or other inflammatory bowel diseases, strictures (scar tissue partially blocking the intestine) are a common complication and can be easily treated via endoscopic methods like lasers or balloon dilation.

In late-stage colorectal cancers that are not planned for surgery, they may sometimes grow so large that the intestine is completely blocked. In such cases, a colonoscopy can be used to insert a stent (a metallic “pipe” structure) to unblock the intestine.

What is the difference between a Colonoscopy and a Gastroscopy in Singapore?

A gastroscopy, also known as an OGD (Oesophago-gastro-duodenoscopy), is similar to a colonoscopy in Singapore, but is used to visualise the appearance of your upper gastrointestinal tract (including the stomach & duodenum) instead.

An OGD is used to look for signs of inflammation, ulcers or masses in the oesophagus, stomach, and part of the small intestine. It is a short procedure, only taking 15-30 minutes.

It also involves inserting a flexible, thin tube down one’s throat, with a camera attached to the end, and similarly allows the doctor to visualise any abnormalities and obtain a biopsy if needed. Pre-OGD preparation includes fasting for at least 6 hours.

Pre - Colonoscopy Preparation

There are a few things you’ll need to do in the days leading up to your colonoscopy, with bowel preparation being the most important. During a colonoscopy, your colon and rectum need to be empty and clear of all stools to give your doctor an unobstructed view. 

In the days leading up to the colonoscopy, you may:

  • Consume a low residue diet (porridge, white rice)
  • Avoid cereal, nuts or juices with fruit pulp
  • Approximately 6 hours before your procedure, you will be made to fast (no food, but able to drink water) and not be allowed to drink any fluids 2 hours prior.

Additionally, to clear your bowels completely, you may be given various laxatives in oral or enema form.

  • Polyethylene glycol-electrolyte solution (PEG) comes in a sachet of powder to mix in a large volume of water (2 litres). It will be taken in two doses: the first dose in the evening before your procedure and the second dose 4-6 hours before your procedure. It is a highly concentrated drink and serves to draw large amounts of water out of your intestines to flush out all faecal matter or undigested food particles. You will have multiple bouts of diarrhoea and may notice your stools become increasingly watery and clear-coloured. Once it has reached that appearance, your bowel preparation is complete.
  • An enema is a liquid laxative that induces an urge to pass motion, and it is generally administered 2-3 hours before the colonoscopy. You will be required to insert the nozzle of the enema bottle into your anus and dispense all the enema solution into your anus (or you may get assistance from your family). Similar to the PEG, it is a highly concentrated solution that will induce the urge to pass motion within 2-5 minutes.

Your doctor may also ask you to stop taking some blood-thinning medications or other medications a few days prior to the test, to reduce the risk of bleeding if polyps are removed during the colonoscopy.

Most patients are given light sedation during the colonoscopy for comfort and may be drowsy afterwards, so you may require someone to accompany you home or arrange for transport after the appointment.

What can I expect during my Colonoscopy in Singapore?

Before the colonoscopy begins, most patients will be given a sedative intravenously to help them feel relaxed and drowsy during the procedure. Once you are adequately sedated, you will be positioned on your side, with your knees curled up to your tummy.

The colonoscope is lubricated with a cool gel to allow for smooth entry into the rectum. It may initially cause a sensation of wanting to defecate when inserted. A small amount of air may be pumped into the large intestine to ‘inflate’ it and allow the doctor to get a better view of the intestinal lining.

If any abnormalities like polyps or masses are found, special tools may be inserted via the scope to remove these. A colonoscopy lasts around 30-45 minutes but may take longer depending on the number of polyps found and removed. The removed biopsy samples will be sent to a lab for testing to ascertain if they are benign (harmless), precancerous or cancerous. These results generally take 1-2 weeks, and your doctor will arrange a follow-up appointment to advise you on the results.

Post - Colonoscopy

Post-Colonoscopy

After the colonoscopy, you will be asked to rest for a while until the sedative wears off, and then you may leave. It is advisable to have someone accompany you home, and you should not drive when drowsy.

Bloating and passing gas more frequently than normal are common after a colonoscopy, as air is pumped into your intestines during the procedure. It generally subsides within the day, and you can relieve the discomfort by walking/moving around.

In the few days after a colonoscopy, you may pass a small amount of blood in your stools, especially if polyps were removed. It should go away within a few days and is not a cause for concern unless it is accompanied by a fever, abdominal pain or a large amount of bleeding.

Are there any side effects and complications to a Colonoscopy procedure in Singapore?

A colonoscopy is generally a safe and routine procedure, but as with any procedure, there are some risks:

  • Bleeding — For routine colonoscopies, the chance of bleeding is approximately 1 in 100. If any polyp removal or biopsies are done, the risk of bleeding is approximately 3%, and you may observe some blood in your stools 1-3 days after the colonoscopy. Major bleeding is extremely rare.
  • Perforation (1 in 1000) — Very rarely, the colonoscope or instrument used to remove polyps may accidentally puncture the wall of the colon or rectum. Depending on the size of the perforation, surgical repair may be required.
  • Anaesthesia — The risk of anaesthesia-related complications is low, as only light sedation is administered.

If you experience any unusual or prolonged side effects after the colonoscopy, do not hesitate to contact your doctor for further advice.

Summary 

A colonoscopy is a simple and routine procedure that is useful in screening for colorectal cancer and can also be used to diagnose or treat other common conditions in the lower gastrointestinal tract.

If you would like to arrange a screening colonoscopy or have abdominal symptoms, do arrange for a consultation with your doctor.

References

  1. Forde, KA. “Therapeutic colonoscopy.” PubMed, https://pubmed.ncbi.nlm.nih.gov/1455873/. Accessed 31 May 2022.
  2. “What is Colonoscopy? | How is a Colonoscopy Done?” American Cancer Society, 14 January 2019, https://www.cancer.org/treatment/understanding-your-diagnosis/tests/endoscopy/colonoscopy.html. Accessed 31 May 2022.

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Dr Benjamin Yip

Consultant Gastroenterologist
MBBS (Singapore), MRCP (UK), MCI (NUS), FRCP (Edin), FASGE (USA), FAMS (Gastroenterology)

Dr Benjamin Yip is a Consultant Gastroenterologist and the Medical Director of the Alpha Digestive & Liver Centre.

Dr Yip believes that gastrointestinal health is hugely interconnected to our whole-body health and sees patients with General Medical, as well as Gastroenterology and Hepatology problems.

His expertise lies in Advanced Endoscopy, including complex endoscopic procedures such as ERCP, EUS, single balloon enteroscopy, Spyglass cholangioscopy and enteral dilation/stenting.

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