During a colonoscopy the endoscopist passes a long flexible tube with a camera on the end through the anus and along the length of the colon. Ideally, the last part of the small bowel (the terminal ileum) should be intubated also – hence the name “ileocolonoscopy” is sometimes used. The images of the inside of these organs are projected on a screen that the endoscopist can view.
Prior to the procedure, the bowel must be prepared for colonoscopy. This means the colon contents need to be cleared out in order for the endoscopist to see better what he/she is doing. Better visibility means an easier colonoscopy, less discomfort for the patient, a greater chance of detecting abnormalities
As with gastroscopy, this procedure is uncomfortable. In addition to sedation administered, care should be taken by the endoscopist to minimize discomfort experienced by the patient. You may be aware during the procedure, as it is not a full anaesthetic. You may also be asked to shift position in order to facilitate advancement of the scope. Pressure may be applied to your abdomen by one of the nursing sisters for the same reason.
Various therapeutic interventions can also be performed using colonoscopy:
- Resection of colonic polyps and precancerous lesions (high grade dysplasia)
- Endomucosal resection of large colonic polyps
- Colonic stenting for colorectal cancer
- Balloon dilatation of ileal and colonic strictures
- Ablation of vascular abnormalities using argon plasma coagulation
- Radiofrequency ablation of radiation proctitis
Whenever procedures are performed, there is a risk of complications. The risk of significant complications from colonoscopy is low. Such complications include:
- Sedation-related complications e.g. over-sedation with suppression of breathing. An antidote will be given in this situation and the procedure will be abandoned.
- Perforation: This can occur either if there is an anatomical abnormaility in the colon or if an intervention is performed e.g. resection of a polyp endoscopically or ablation of a vascular lesion using argon plasma coagulation. If perforation occurs, it is considered an emergency and an operation may need to be performed.
- Bleeding: If a polyp is resected or if a lesion is biopsied, it may cause significant bleeding. Usually this is dealt with during the colonoscopy, but bleeding can occur up to two weeks later and a repeat procedure may be required to stop the bleeding.