A colonoscopy is a medical procedure used for screening, diagnosis, and prevention of colorectal cancer by examining the inside lining of the large intestine. It involves inserting a flexible tube, the colonoscope, which has a camera and light source, through the rectum. The physician primarily responsible for performing this examination is a Gastroenterologist, a specialist dedicated to the digestive tract. This allows the doctor to visually inspect the colon for abnormal growths, such as polyps, which are removed during the procedure to prevent cancer.
The Specialists Qualified to Perform Colonoscopies
The Gastroenterologist (GI) is the dedicated expert due to their extensive, focused training. After medical school and a three-year internal medicine residency, these physicians undergo a specialized three-year fellowship in gastroenterology. This fellowship focuses on the anatomy, physiology, and diseases of the gastrointestinal tract, including advanced training in endoscopic procedures.
During their fellowship, a GI trainee typically performs a large volume of procedures, often completing 500 or more colonoscopies to achieve procedural competence. This high volume of experience develops the technical skill required to navigate the entire colon and the visual acumen necessary to detect subtle polyps. Expertise also includes the safe administration of sedation and the management of complications, such as bleeding or perforation, which may arise during the examination.
While Gastroenterologists are the primary providers, the procedure may also be performed by certain specialized General Surgeons. These surgeons are trained to perform surgical procedures on the colon and may be credentialed to perform colonoscopies, particularly for diagnostic reasons. In some rural areas, a small number of Family Medicine physicians who have completed specialized training may also be granted credentials. However, the depth of training and lifetime procedural volume generally positions the Gastroenterologist as the most experienced practitioner for this procedure.
Essential Preparation Steps Before the Procedure
The success of a colonoscopy depends almost entirely on the patient’s adherence to the bowel preparation instructions, which is designed to completely cleanse the colon. Physicians require the colon walls to be free of residual stool so they can clearly visualize the mucosal lining and detect small polyps, which may be only a few millimeters in size. Preparation begins several days before the appointment with a low-residue diet, eliminating high-fiber foods like whole grains, nuts, seeds, and raw fruits or vegetables.
The day before the procedure, the diet transitions to exclusively clear liquids, such as broth, clear juices, sports drinks, and gelatin, and patients must avoid all solid food. It is also important to avoid any liquids with red or purple dyes, as these can be mistaken for blood in the colon. The cleansing process itself involves consuming a prescription-strength laxative solution, often split into two doses—one taken the evening before and the second taken a few hours before the scheduled appointment.
This split-dose regimen is more effective at clearing the colon and is associated with better visualization quality than a single large dose. Patients must discuss and potentially adjust their regular medications with the prescribing physician. This is particularly important for blood thinners, which increase the risk of bleeding, and diabetes medications, which may need alteration due to the restricted diet. Inadequate preparation often results in the need to reschedule the examination, delaying screening.
What to Expect During and Immediately After the Procedure
Upon arrival, an intravenous line will be placed to administer a sedative, which is often Propofol delivered under a protocol known as Monitored Anesthesia Care (MAC). This level of sedation ensures the patient is deeply asleep and comfortable, experiencing no pain or memory of the examination, which typically lasts between 15 and 30 minutes. The physician carefully advances the colonoscope through the large intestine, inflating the colon with air or carbon dioxide to allow for a comprehensive view of the walls.
If the physician identifies a polyp, specialized instruments passed through the scope are used to remove the growth, a process called a polypectomy, or to take a tissue sample for biopsy. Following the examination, the patient is moved to a recovery area and monitored for approximately one to two hours as the effects of the sedation dissipate. It is common to experience bloating or cramping immediately afterward due to the air introduced during the procedure, which is relieved by passing gas.
Because of the sedation, patients are strictly prohibited from driving, operating heavy machinery, or making important decisions for the remainder of the day. A responsible adult must be present to escort the patient home from the facility. Patients can usually resume a normal diet and activities the day after the procedure, with the final results of any biopsies typically communicated by the physician within one to two weeks.