Individuals with first degree relatives diagnosed with colon cancer are encouraged to undergo their first colonoscopy at age 40, or 10 years prior to the age the relative was diagnosed, whichever comes first. Examples of high-risk populations include a history of inflammatory bowel disease, a family history of colorectal cancer at age <60 years, hereditary polyposis (Such as Peutz Jegher syndrome and Familial Adenomatous Polyposis, caused by an APC gene mutation) and non-polyposis syndromes (LYNCH I and II), and surveillance after resection of colorectal cancer. Patients with a high risk of developing colorectal cancer receive the screening procedure before the age of 50 years, and it is repeated every 1, 2, or 5 years based upon the primary risk and findings during the procedure. Earlier surveillance is performed depending on the results of the first (index) procedure. The subsequent colonoscopies are called surveillance colonoscopies. Patients will receive a repeat colonoscopy at 10-year intervals to continue to screen for colorectal cancer or pre-malignant lesions. Average risk screening starts at the age of 50 and is performed at least every 10 years, as long as the colonoscopy results were unremarkable or no pathology identified that would place the patient at a higher risk. Screening colonoscopies are performed to assess for colorectal cancers based upon a patient's risk (average vs. Diagnostic indications can further be classified as screening vs. It can be divided into diagnostic and therapeutic indications. The colon, like the small intestine, is made up of various layers (from intraluminal to extraluminal):Ĭolonoscopy can be performed for multiple reasons. Again, this is important to know when surgical intervention is required, and appropriate anatomic resections are considered. The small intestines, cecum, ascending colon, and proximal two-thirds of the transverse colon are supplied by the SMA, while the distal one-third, descending colon, sigmoid colon, and proximal rectum are all supplied by the IMA.

The SMA and IMA further branch into several other arteries that supply different components of the colon (Media 1 and 2). There are two primary arteries that supply the colon with blood, the superior mesenteric artery (SMA), and the inferior mesenteric artery (IMA). This is important to remember when navigating through a colonoscopy and identifying the location within the colon. As a general rule of thumb, the diameter of the cecum, transverse colon, and descending colon are 9 cm, 6 cm, and 3 cm, respectively. The ascending colon, hepatic flexure, and transverse colon constitute the right colon, whereas the descending colon, splenic flexure, and sigmoid make the left colon. The total distance from the anus to the cecum varies from male to female but can be generalized at around 120 cm to 160 cm. The colon opens into the rectum, which terminates as the anal canal. This is called the cecum, which is a pouch-like structure and further continues as ascending colon, followed by the transverse, descending, and the sigmoid colon. The ileum ends at the ileocecal valve, which opens into the first part of the large intestine. Going from proximal to distal, the small intestine is further divided into the duodenum, jejunum, and ileum. The part of our gastrointestinal system after the stomach is divided into the small and the large intestine. This is important to remember when it comes to lesions and pathology throughout the colon, as this will help decide future surgical planning, especially with the colon. Respectively, the foregut consists of the mouth to the second portion of the duodenum (part of the small intestine), the midgut consists of the remaining duodenum (third and fourth portion) to about two-thirds the distance of the transverse colon and the hindgut consists of the distal one-third colon to the anus. The gastrointestinal system is divided into the foregut, midgut, and hindgut.

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