Colonoscopy

What is a colonoscopy?

The colon is about 3 to 5 feet long. It travels from the lower right corner of the abdomen (where the small intestine ends) up to the liver, across the body to the spleen in the upper left corner and then down to form the rectum and anus. A colonoscopy is a procedure performed by a specialist surgeon to see inside your colon (large intestine or large bowel). The instrument used in this investigation is called a colonoscope. It is a flexible tube and has a diameter of that of the little finger.

Within each colonoscope is an illumination channel which enables light to be directed onto the lining of your large bowel and another which relays pictures back to the endoscopist onto a television screen. During the investigation, the doctor may need to take some tissue samples (biopsies) from the lining of your bowel for analysis: this is painless. A video recording and/ or photographs may be taken for your records. It is necessary to abstain from food for 24 hours and you will be given a special solution to mix with your fluids during this 24 hour period to clean your bowel (bowel prep).

Indications for diagnostic colonoscopy:

Evaluation of gastrointestinal bleeding

  • Haemoccult positive stools
  • Anorectal bleeding the cause of which is not certain
  • Melena after excluding an upper gastrointestinal tract source
  • Unexplained iron deficiency anaemia

Surveillance of colon neoplasm or cancer

  • Following resection of carcinoma or neoplastic/adenomatous polyp
  • In patients at high risk of cancer
  • First degree relatives or multiple family members with colon cancer, adenomatous polyps, or polyposis syndromes
  • Cancer family syndrome
  • Chronic ulcerative colitis with pancolitis greater than 7 years or left sided colitis of greater than 10 years

Inflammatory bowel disease

  • Determination of extent of disease
  • Confirmation of diagnosis
  • Cancer surveillance in chronic ulcerative colitis

For evaluation of:

  • Clinically significant abnormalities of barium enema/CT
  • Clinically significant diarrhoea or unexplained aetiology
  • Suspected ischaemic colitis
  • Intraoperative localisation of lesion not apparent at Surgery

Where is a Colonoscopy done?

A colonoscopy is performed in either a day surgery or hospital. Time required for the colonoscopy will vary with individual circumstances, but typically takes approximately 30 minutes with 1-4 hours recovery time following the procedure because sedation has been administered.

Who is involved?

  • Healthcare professionals usually involved in the procedure are:
  • Specialist surgeons
  • Anaesthetist – a Colonoscopy does not require a general anaesthetic however it does require intravenous sedation given by the anaesthetist
  • A pathologist may conduct analysis of any specimens collected
  • Nurses will assist during the procedure and recovery

How to prepare (Bowel prep)

Preparation involves taking a special solution to help clean out your bowel. This facilitates the specialist having the best possible view whilst carrying out the procedure. You will be given details and education on how to take the bowel prep for your colonoscopy by the practice nurse. You will also be given the opportunity to have any questions answered in relation to the procedure or hospital admission.

Risks associated with the procedure

  • Colonic perforation – the risk of perforation of the colon is 0.2-0.4% after diagnostic colonoscopy and 0.3-1.0% with polypectomy
  • Immediate or delayed bleeding – Bleeding complicates approximately 1 of every 1000 colonoscopic procedures. Most cases resolve spontaneously. Following polypectomy, bleeding may occur immediately, but, in 30-50% of cases, it is delayed from 2-7 days until the eschar sloughs.
  • Transmission of infection – Documented instances of transmission of infection from one patient to another or to endoscopic personnel are extremely rare.
  • Abdominal distention – Colonic distention during colonoscopy can cause notable discomfort and may also impair mucosal blood flow. Insufflation of carbon dioxide rather than air during colonoscopy may offer some advantages: carbon dioxide is absorbed from the colon, it is non-explosive, and mucosal blood flow is less affected, thus decreasing the risk of colonic ischemia.
  • Postpolypectomy coagulation syndrome – The combination of pain, peritoneal irritation, leukocytosis, and fever after colonoscopy may represent a postpolypectomy burn injury. A conservative approach generally leads to a good outcome.
  • Splenic rupture – Although a very uncommon complication, the presumed mechanisms of splenic rupture during colonoscopy include direct trauma to the spleen, marked angulation of the splenic flexure, excessive splenocolic ligament traction, and decrease in the relative mobility between the spleen and the colon.
  • Small bowel obstruction – Small bowel obstruction is another rare complication of colonoscopy, although it is perhaps more common in patients who have a history of abdominal surgery and postoperative adhesions.
  • Incomplete colonoscopy – An incomplete colonoscopy examination may occur in up to 5-10 percent of cases and may be due to patient discomfort, a colon with many twists, postoperative adhesions, or hernias, poor bowel prep, colonic obstruction, looping, diverticular disease, adverse events and other causes
  • Missed lesion during colonoscopy – The most recent multicentre study reported that the miss rate for polyps of all types and sizes was 28%.
  • Medication effects – Sedatives used during colonoscopy may cause complications from allergic reactions or, more importantly, from doses that may be excessive for certain individuals and lead to respiratory depression. Serious events may complicate up to 0.5% of procedures. More than 50% of deaths associated with endoscopy are related to cardiopulmonary events.

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