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.
Twilight sedation is, however, inherently safer than general anesthesia; it also allows the patients to follow simple commands and even to watch the procedure on a closed-circuit monitor. Tens of millions of adults annually need to have colonoscopies, and yet many dont because of concerns about the procedure.Colonoscopy can be carried out without any sedation and without problems with pain, which is practised in several institutions in many countries with the patients agreement. This allows the patient to shift the body position to help the doctor carry out the procedure and significantly reduces recovery time and side-effects. There is some discomfort when the colon is distended with air, but this is not usually particularly painful, and it passes relatively quickly. Unsedated patients can be released from the hospital on their own without any feelings of nausea, able to continue with normal activities, and without the need for an escort as recommended after sedation. Ultrasound
Duodenography and colonography are performed like a standard abdominal examination using B-mode and color flow Doppler ultrasonography using a low frequency transducer — for example a 2.5 MHz — and a high frequency transducer, for example a 7.5 MHz probe. Detailed examination of duodenal walls and folds, colonic walls and haustra was performed using a 7.5 MHz probe. Deeply located abdominal structures were examined using 2.5 MHz probe. All ultrasound examinations are performed after overnight fasting (for at least 16 hours) using standard scanning procedure. Subjects are examined with and without water contrast.