A colonoscopy is a medical procedure used to examine the entire inner lining of the large intestine using a long, flexible tube called a colonoscope. The colonoscope has a camera and light source, allowing the physician to view the lining. The primary purpose of this procedure is to screen for colorectal cancer by identifying and removing precancerous growths known as polyps. A colonoscopy is also used to investigate digestive symptoms, such as changes in bowel habits, chronic diarrhea, or rectal bleeding, and to diagnose conditions like inflammatory bowel disease.
Preparing for the Procedure
The success of the colonoscopy depends heavily on thorough bowel preparation, which aims to clear all solid matter from the colon. This preparation usually begins several days before the procedure with a switch to a low-fiber, low-residue diet. This means temporarily avoiding high-fiber foods such as whole grains, nuts, seeds, and raw fruits and vegetables.
The day before the colonoscopy, the diet must be restricted to clear liquids. Fluids include clear broth, water, plain tea or coffee without milk, and sports drinks. Red, blue, or purple liquids are generally avoided as their dyes can mimic blood in the colon. Patients must also discuss medications with their doctor; certain supplements like iron and anti-diarrheal medicines must be stopped about a week before, and blood thinners may need to be temporarily paused.
The most intensive part of the preparation involves consuming a prescription laxative solution, often in a split-dose regimen. The first half is typically taken the evening before, and the second half is consumed early on the morning of the procedure. This strong laxative causes frequent, watery bowel movements until the colon is completely flushed. The goal is for the discharge to be a clear or yellowish liquid, indicating the colon is clean enough for the physician to see the lining clearly.
The Day of the Colonoscopy
Upon arrival, patients check in and are taken to a preparation area where they change into a gown. A nurse will place an intravenous (IV) line to administer fluids and sedative medication. Before the procedure, the patient will speak with the gastroenterologist and a member of the anesthesia team to review the medical history.
Most patients receive deep sedation, often Monitored Anesthesia Care (MAC) using a fast-acting medication like Propofol, which allows them to sleep comfortably through the procedure. The procedure itself is relatively brief, typically lasting between 15 to 30 minutes, though the entire appointment usually takes two to three hours.
During the examination, the patient is positioned on their side. The doctor slowly advances the colonoscope through the large intestine while gently inflating the colon with air or carbon dioxide to expand the walls. This allows a better view of the lining. If the doctor finds a polyp, it is removed immediately using instruments passed through the scope. Tissue samples (biopsies) can also be taken for laboratory analysis.
Immediate Post-Procedure Care and Results
Immediately following the procedure, the patient is moved to a recovery area where nurses monitor vital signs as the sedation wears off. The sedative effect causes grogginess, dizziness, and mild confusion. A responsible adult must be present to drive the patient home and stay with them for several hours. Patients are instructed not to drive, operate machinery, or sign legal documents for the following 24 hours.
Abdominal bloating, cramping, or gas is common, resulting from the air or carbon dioxide used to inflate the colon. Moving around and walking gently helps the body expel this residual gas more quickly. Patients can usually resume a normal diet after the procedure.
The gastroenterologist will provide immediate preliminary results in the recovery area, such as whether any polyps were found and removed. If biopsies or polyps were taken, the tissue is sent to a pathology lab for detailed analysis. The final pathology results are typically delivered within one to two weeks of the procedure.