Approximately one to two days before a colonoscopy, patients only consume full or clear liquids and are required to drink a laxative, explains The Merck Manual Professional Edition. Most laxative preparations include a gallon of an electrolyte solution that patients have to drink within 3 to 4 hours.
Patients who cannot tolerate the electrolyte solution can be given magnesium citrate, sodium phosphate, polyethylene glycol, lactulose, or other laxatives, according to The Merck Manual Professional Edition. A colonoscopy usually lasts between 15 and 60 minutes, and most patients receive sedation that helps them relax and not feel pain, explains MedicineNet.
During the procedure, the patient is placed on his or her side and the doctor slowly advances a colonoscope until it reaches the last portion of the small intestine, according to MedicineNet. Abnormalities that are found in the colon, such as polyps, are usually removed with forceps and sent for a biopsy. A pathologist examines the biopsy samples under a microscope and writes a report regarding their nature.
A common reason that patients undergo the procedure is to identify the cause of gastrointestinal bleeding, notes MedicineNet. Other indications include abdominal pain, diarrhea and a change in bowel habits. Colonoscopies are also used to explore abnormalities found on CAT scans.