A meta-analysis found that playing music improves tolerability to patients of the procedure.The first step is usually a digital rectal examination, to examine the tone of the sphincter and to determine if preparation has been adequate. The endoscope is then passed through the anus up the rectum, the colon (sigmoid, descending, transverse and ascending colon, the cecum), and ultimately the terminal ileum. The endoscope has a movable tip and multiple channels for instrumentation, air, suction and light. The bowel is occasionally insufflated with air to maximize visibility (a procedure that gives the patient the false sensation of needing to take a bowel movement). Biopsies are frequently taken for histology. Additionally in a procedure known as chromoendoscopy, a contrast-dye (such as indigo carmine) may be sprayed through the endoscope onto the bowel wall to help visualise any abnormalities in the mucosal morphology. A Cochrane review updated in 2016 found strong evidence that chromoscopy enhances the detection of cancerous tumours in the colon and rectum.In most experienced hands, the endoscope is advanced to the junction of where the colon and small bowel join up (cecum) in under 10 minutes in 95% of cases. Due to tight turns and redundancy in areas of the colon that are not "fixed", loops may form in which advancement of the endoscope creates a "bowing" effect that causes the tip to actually retract. These loops often result in discomfort due to stretching of the colon and its associated mesentery.
Recommendations
The American Cancer Society recommends, beginning at age 45, both men and women follow one of these testing schedules for screening to find colon polyps and/or cancer:
Flexible sigmoidoscopy every 5 years, or
Colonoscopy every 10 years, or
Double-contrast barium enema every 5 years, or
CT colonography (virtual colonoscopy) every 5 years
Yearly guaiac-based fecal occult blood test (gFOBT)
Yearly fecal immunochemical test (FIT)
Stool DNA test (sDNA) every 3 years

Medicare coverage
In the United States, Medicare insurance covers the following colorectal-cancer screening tests:
Colonoscopy: average risk — every 10 years beginning at age 50, high risk — every 2 years with no age restriction
Flexible sigmoidoscopy — every 4 years beginning at age 50
Double-contrast barium enema: average risk  — every 4 years beginning at age 50, high risk — every 2 years
(CT) colongraphy: not covered by Medicare
gFOBT: average risk — every year beginning at age 50
FIT: average risk — every year beginning at age 50
Cologuard: average risk — every 3 years beginning at age 50

Risks
About 1 in 200 people who undergo a colonoscopy experience a serious complication. Perforation of the colon occurs in about 1 in 2000 procedures, bleeding in 2.6 per 1000, and death in 3 per 100,000, with an overall risk of serious complications of 0.35%.In some low-risk populations screening by colonoscopy in the absence of symptoms does not outweigh the risks of the procedure.