Colonoscopy should be performed as the initial investigation when looking for possible colonic causes of iron deficiency anaemia or occult blood in the faeces. Thorough investigation of these patients and endoscopic follow-up of adenoma patients is the key to an early diagnosis and treatment as well as prevention of colon cancer.
Readiness for polypectomy is required in all facilities performing colonoscopies.
As a rule, the indication for sigmoidoscopy is the monitoring or treatment of changes detected earlier. Colonoscopy should be performed in all patients who are suspected to have a condition originating in the colon.
Colonoscopies are also performed on bowel cancer screening patients who have a positive result on a faecal occult blood test.
Colonoscopy or sigmoidoscopy should usually be performed on patients over 50 years of age.
Proctoscopy is sufficient for younger patients if an anal fissure Anal Fissure or typical haemorrhoids Haemorrhoids are detected and the symptoms are consistent with these findings.
Iron deficiency anaemia of unknown origin
Occult blood in faeces, and the patient has no epigastric symptoms indicating gastroscopy as the first examination.
Chronic diarrhoea: suspicion of inflammatory bowel disease (proctitis, ulcerative colitis or Crohn's disease) according to the patient's symptoms.
Faecal calprotectin is suitable as the first-line test when an inflammatory bowel disease is suspected.
If the patient has diarrhoea or bloody diarrhoea after a course of antimicrobials, a nucleic acid test for the Clostridioides difficile toxin gene is sufficient as the initial diagnostic investigation.
Even if a patient with diarrhoea has a normal appearing colonic mucosa, a biopsy must always be performed in order to diagnose colitis.
A change in bowel habits in a person above 50 years of age, particularly if the patient also has abdominal discomfort. In younger persons, IBS diagnosis can be set without colonoscopy, provided that the Rome criteria are fulfilled Functional Bowel Disorders and the Irritable Bowel Syndrome (IBS).
Colonoscopy as a (repeated) follow-up study is indicated
in chronic colitis with symptoms to assess its activity and extent.
Colonoscopy as therapeutic intervention: e.g.
polypectomy
argon therapy in radiation proctitis
faecal transplantation in Clostridioides difficile infection
dilations
stents
treatment of Ogilvie's syndrome
Cases where colonoscopy/sigmoidoscopy is not the first examination
If abdominal pain is the only symptom, a CT scan can in these kind of cases be the primary examination to detect a tumour, for example.
Melena (black, tar-like faeces). The most common cause is upper gastrointestinal bleeding, and gastroscopy should be performed first.
If the patient has symptoms suggesting lactose intolerance, a diet without lactose should be tried first.
Long-term lower abdominal symptoms (irritable bowel symptoms often commence already at a young age and are periodical).
Patients in whom a previously performed colonoscopy showed normal findings have a significantly lower risk of colorectal cancer than those in whom an endoscopy has not been performed during a 10-20-year follow-up time. If a reliable colonoscopy with normal findings has been performed earlier, a repeated endoscopy is usually not necessary. If, however, the patient develops new symptoms like melaena, iron deficiency anaemia or prolonged diarrhoea, colonoscopy should be repeated.
If a faecal occult blood test is negative in a bowel cancer screening test and the patient has no alarming symptoms.
Preparing the patient for colonoscopy/sigmoidoscopy
The patient avoids berries and vegetables with seeds (tomatoes, whortleberries, cucumber) and linseed for one week preceding the examination.
The only drink from the evening before the examination is water or mineral water. No other food during that time.
Primary health care services should include readiness to sigmoidoscopy. The investigation is relatively easy to learn. Colonoscopy requires a longer period of education.
The patient lies on his left side with hips and knees slightly flexed.
Touch per rectum is performed first to detect lesions near the anus. If something is felt by finger, a proctoscopy should be performed first. Eventual biopsies from the rectum are not taken until the endoscopy has been completely carried out.
The tip of the instrument is lubricated with lidocaine gel before insertion into the ampulla.
The lumen is made visible by infusing air or carbon dioxide into the bowel. The instrument can be advanced only after the lumen has become visible, and visual control must be maintained always when the instrument is passed on. Advancing the instrument blindly may result in the tip passing into a diverticulum and perforating the bowel. The instrument is passed on to its maximal range without delay, and the bowel is inspected during retraction of the instrument. If a lesion is seen during insertion its position should be recorded.
If the lumen disappears and cannot be found when bending the instrument and infusing more air the instrument should be returned a few centimeters until the lumen is again visible. If the insertion of the instrument does not succeed the patient should change to supine position with the hips and knees flexed and heels on the examination table. The change of position may straighten the bends of the bowel.
After the instrument has been inserted into its maximal range (or a bend in the bowel prevents advancing it despite repeated attempts) the inspection is started by slowly pulling the instrument back while bending its tip to see the entire mucosa.
Biopsies should be taken from macroscopically suspect sites (usually at least 2 biopsies from one site, even more from an adenoma). If the mucosa looks normal to the experienced eye, histology rarely detects anything abnormal. Routine biopsies need not be taken unless the patient has diarrhoea. In a patient with diarrhoea, it is worth taking biopsies even on a normal-appearing mucosa. A small polyp can be totally removed with the biopsy forceps. Several biopsies should be taken from larger tumours. If the mucosa looks inflamed (unglossy, bleeding, membranotic) biopsies should be taken both from the abnormal mucosa as well as from normal-appearing mucosa surrounding it. Report the distance from the anus, or otherwise describe the place where the biopsies were taken, on the biopsy containers.
If the examination is performed as follow-up of an inflammatory bowel disease always take biopsies even if the bowel looks normal.
Findings of clinical importance
Polyps (adenomas and serrated polyps) as well as tumours
Ulcerations
Membranes that cannot be rinsed away or the removal of which causes bleeding.
Petecchiae or bleeding on light touch of the instrument
Unglossy appearance of the mucosa, lack of normal vascular pattern