The information on this page was reviewed and approved by
Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on August 23, 2021.

Colonoscopy and endoscopic procedures for colorectal cancer

A gastroenterologist uses a colonoscopy to examine the inner lining of the colon and rectum, which make up the large intestine. In this endoscopic procedure, a colonoscope—a long, flexible, lighted tube with a tiny camera attached to the end—is inserted into the rectum. The gastroenterologist guides the colonoscope through the colon, looking for polyps, signs of bleeding, inflammation or other abnormalities.

If the gastroenterologist finds polyps, or small growths inside the colon or rectum, a polypectomy may be performed during the colonoscopy. The polyps are then analyzed in a laboratory for signs of cancer.

A patient may have a colonoscopy as an outpatient. The procedure typically takes 15 to 60 minutes, but patients usually remain onsite for two to three hours, including preparation and recovery time. Patients are often sedated during the procedure to help them relax and tolerate discomfort. They may experience pressure, bloating or cramping during or after the procedure, but rarely do patients experience pain.

In addition to a colonoscopy, endoscopic procedures used to diagnose colorectal cancer include:

Flexible sigmoidoscopy: For this procedure, a gastroenterologist uses a lighted tube with a tiny camera attached to its end to examine the rectum and lower part of the colon (the sigmoid colon) for polyps or other abnormalities. The gastroenterologist may also perform a biopsy to collect samples of tissues or cells for further investigation. This colorectal cancer detection test is an outpatient procedure that does not typically require pain medication or sedative anesthesia.

Endoscopic ultrasound (EUS): A gastroenterologist uses this procedure to carefully examine the digestive tract and nearby organs, including the pancreas, liver, gallbladder and bile duct. This high-resolution imaging technology helps detect potential tumors and identify lymph nodes in the chest and abdomen, where the cancer may have spread. A very thin needle is used to obtain tissue samples, which are analyzed to determine whether cancer cells are present. Sometimes, doctors use an EUS to stage rectal cancer and determine an appropriate treatment plan.

Next topic: What are the lab testing options for colorectal cancer?