Colonoscopy

Introduction

What is it and why is it done?

A colonoscopy can be carried out for diagnosis (finding out what's wrong) and treatment of medical problems concerning the large bowel such as inflammatory bowel disease (IBD), diverticular disease and polyps (1). Most commonly, a colonoscopy is requested by your doctor if you have bowel symptoms, such as:

Blood in your stools

Diarrhoea that does not resolve

Persistent pain in your tummy

Unexplained anaemia (low blood count)

Abnormal findings on imaging scans such as CT

Finally, a colonoscopy may be useful for treatment reasons such as removing polyps or screening for colon cancer in patients with IBD (1).

Will I need any preparation?

A number of preparation steps need to be taken prior to your colonoscopy. These include:

1. Diet: your doctor will ask that you take a special diet for a few days before the colonoscopy. This will include avoiding foods that are high in fibre (e.g. whole grains) and red-coloured drinks (e.g. berry juices) and ask you to eat plain foods (e.g. white bread). You should also drink plenty of clear fluids such as water, ices and clear soups. A diet low in fibre prior to a colonoscopy has been shown to make patients more comfortable during the bowel preparation process (9). Furthermore, a recent research trial has even shown that a low-fibre diet can even improve the success of bowel preparation (10). You should also avoid all food and drink 4-6 hours before your colonoscopy.

2. Bowel preparation: this is needed to allow your doctor/nurse the best chance to see any abnormal areas. It has been shown in studies that inadequate preparation of the large bowel has a 47.9% missed rate per polyp (11). Large reviews have also shown that good bowel preparation can reduce the risk of complications, reduce the length of the procedure time, and avoid repeat colonoscopies because of inadequate preparation, making this an important step in the preparation process (12). In order clean out your colon, your doctor will prescribe a liquid preparation of laxatives to be taken a day before the colonoscopy. Typically, this is a single sachet but sometimes more than 1 sachet can be given to increase the likelihood of a successful bowel preparation. This can be an uncomfortable experience as you will likely need the bathroom frequently and will experience diarrhoea, which is completely normal.

3. If you take any regular medications, you should check with your doctor if these need to be stopped prior to the test.

Technique

Anaesthesia

General anaesthetic is rarely used as most patients cope well with the colonoscopy, and deep anaesthesia can sometimes increase your risk of complications during the procedure (13). However, you may be offered sedation, a form of medication that can make you feel calm and relaxed during the procedure. You doctor will discuss the sedation options, but depending on your preference and the potential risks of sedation, you may be advised to have no sedation or mild to moderate sedation. Most commonly, colonoscopies are undertaken under a form of sedation (14).

What does it involve?

Prior to the procedure, your doctor will prescribe bowel preparation, which you will need to take to clear your colon to allow the doctor or nurse to fully examine and look for any areas of abnormalities (more details in “will I need any preparation”).

On the day of the colonoscopy, you will be asked to come in as an outpatient and given some sedation through a line in your vein. Some patients prefer not to have any sedation. In exceptional circumstances, the doctor may request for a general anaesthetic to be used but this is not common practice. 

During the procedure you will be laying on a couch and the doctor or nurse will gently pass the colonoscope through the rectum and into the rest of the colon. 

To allow visualisation of the bowel, carbon dioxide air and water is passed down one of the channels on the colonoscope. This can be uncomfortable and may make you feel bloated or as if you need to pass stool. Often, patients can pass wind during the procedure but these symptoms are a completely normal part of the test so there is no need to feel embarrassed. 

The procedure follows a sequence of steps. These steps follow closely the regions of the colon.

1. Insertion and assessment of the rectum.

Insertion of the scope through the anus provides a view of the rectum, the rectum has a number of 'curtains' which cover the lumen (central channel) of the rectum. These curtains require the scope to be negotiated from side to side to achieve progress.

The tip of the scope can be 'retroverted' or bent back on itself to provide a view 'around the corner' of where the rectum was entered through the anus.

2. Assessment of Sigmoid colon and descending colon.

The Sigmoid colon is often very lax and tends to hang from the back of the abdominal wall. This results in a sharp bends as the sigmoid colon gives way to the descending colon. Negotiating these sharp bends can be uncomfortable. Discomfort is sometimes related to the scope forming a 'loop' inside the colon. A common type of loop formed here is called an 'alpha' loop. These loops should be removed by combining forward movements with withdrawal of the scope and avoiding over-inflating the colon.

3. Crossing the splenic flexure to assess the transverse colon.

Crossing the splenic flexure to enter the transverse colon is relatively straightforward is the scope is straight with minimal loop. The tip of the scope is angled to face the centre of the transverse colon and it is advanced. Crossing the transverse colon can result in a 'gamma' loop forming in the sigmoid colon. This can be improved by suctioning, withdrawal of the scope and external pressure on the tummy on the left hand side.

4. Crossing the hepatic flexure to assess the ascending colon.

As much of the scope is already in the patient at this point, it is difficult to apply much torque to the scope at this point. Pressure on the left upper quadrant of the belly or changing the patient position to lying on your back or front can be helpful.

5. Assessment of the Caecum and crossing the ilio-caecal valve.

To complete the colonoscopy the caecum should be inspected. To confirm that the colonoscopy has been completed, the small bowel can be entered through the Ilio-caecal valve. A biopsy of the ileum is often taken as proof positive that this region has been reached as it is characteristic.

6. Withdrawal of the scope.

Time taken for withdrawal has been associated with a higher detection rate. The withdrawal process should be methodical and used to inspect the entire bowel wall.

Depending on the reason for the procedure, the doctor or nurse may take biopsies (samples) which will be sent to the lab for analysis or, may remove any polyps or tissue found. This should not be painful as the bowel lining has no nerve endings.

How long does it take? 

The test should only take 30 minutes but may last an hour or so depending on the difficulty of the procedure and whether biopsies need to be taken from the lining of the bowel.

Post procedure course (follow-up)

After the procedure, you will be monitored in a recovery area and observed for 30 minutes to 1 hour until the effects of the sedative have worn off. In the first few hours after the colonoscopy, it is normal to continue to feel bloated, pass wind or experience cramps. You may also have some fresh red blood in your stool or when you wipe your bottom. It is also common to feel tired and sleepy due to the sedative effects and it is recommended that you have someone accompany you home. You should not drive, operate heavy machinery or return to work that day. 

The doctor or nurse may give you information regarding your colonoscopy after your procedure but a report is sent to the doctor who originally requested the test and any biopsies are analysed and results included in the report.

How long will I stay in hospital?

Colonoscopies are typically done as day case procedures (go home the same day). Once the colonoscopy has been completed, you will be kept in “recovery” if you have had a sedative. If there have been no complications, you may then return home after an hour of observation. Most patients feel they are able to return to normal after 24 hours.

What care will I need at home?

 No particular care at home is needed.

Will I need someone to stay with me?

 It is recommended that you are accompanied home as you may feel drowsy for the first 24 hours.

Will I need any special equipment when I go home?

No particular equipment is needed.

What follow up care is needed? 

This is dependant on the finding from the colonoscopy itself and also the results from any biopsies taken during the procedure.

You should keep an eye out for the following symptoms in the first few days after a colonoscopy:

Severe abdominal pain

Severe bleeding from the back passage

Not being able to pass any stool and wind.

When can I start my normal activities again (e.g. driving, sports or work?)

 You should not drive, operate heavy machinery, go to work or make any important decisions.

Where can I find more information?

Further information can be found below:

Patient Information – Colonoscopy: https://patient.info/cancer/colon-rectal-bowel-cancer-colorectal/colonoscopy

NHS Conditions – Colonoscopy: https://www.nhs.uk/conditions/colonoscopy/

National Library of Medicine – Colonoscopy: https://medlineplus.gov/colonoscopy.html

Alternatives to a Colonoscopy

CT Pneumocolon, also referred to as CT colonography or Virtual Colonoscopy, is an alternative procedure. This is a test that uses a computerised tomography (CT) scanner to produce images of your large bowel. This can provide some of the information normally obtained by a colonoscopy, such as detection of polyps or lesions that may be indicative of colon cancer (15). This is considered a less invasive procedure as it does not involve insertion of a colonoscope, but bowel preparation and pumping of the bowel with carbon dioxide air is still required. This is a test that is typically used in patients who are too old or frail for a colonoscopy, or have other circumstances that would prevent them from having a colonoscopy.