What is sigmoidoscopy?
Sigmoidoscopy is an endoscopic procedure that examines the sigmoid colon and rectum.
Your doctor may recommend a sigmoidoscopy for several reasons:
- To determine the cause of changes in bowel habits
- Abdominal pain
- Rectal bleeding
- Weight loss
How does sigmoidoscopy differ from colonoscopy?
Sigmoidoscopy allows the doctor to see the lower part of the large intestine, while colonoscopy enables examination of the entire large intestine. Colonoscopy is the preferred method for screening for colorectal and rectal cancers.
How is a sigmoidoscopy performed?
Examining the sigmoid colon
Patients may need to receive an intravenous (IV) sedative before the procedure. Sedatives help patients remain relaxed and comfortable. While patients are sedated, the doctor and medical staff monitor vital signs. During a sigmoidoscopy, patients lie on their left side and are connected to a monitor that records their vital signs.
The doctor inserts a long, flexible tube called a sigmoidoscope into the rectum and slowly advances it through the rectum into the sigmoid colon. The endoscope inflates the colon with air to give the doctor a better view. A small camera transmits video images from the inside of the large intestine to a computer screen, allowing the doctor to closely examine the inner lining of the sigmoid colon and rectum. The doctor may ask the patient to shift positions periodically for better visualization. Once the endoscope reaches the transverse colon, it is slowly withdrawn while the bowel is carefully re-examined.
Biopsy and removal of colon polyps
The doctor may remove small growths, called polyps, during the sigmoidoscopy using special tools that pass through the endoscope. Polyps are common in adults and are initially harmless. However, most colorectal cancers start as polyps, so removing them early is an effective way to prevent cancer.
If bleeding occurs, the doctor can usually stop it with a special catheter or medication through the endoscope. During a sigmoidoscopy, the doctor may also take samples of tissues that appear abnormal. This process is called a biopsy and allows the doctor to later examine the tissue under a microscope for potential signs of disease. The removal of tissue and treatments to stop bleeding are typically painless. If polyps or other abnormalities are found, the doctor may recommend examining the rest of the large intestine with a colonoscopy.
After the exam
A sigmoidoscopy lasts about 15 to 20 minutes. Cramping or bloating may be felt for up to an hour after the procedure. Bleeding and perforation of the large intestine are possible but extremely rare complications. Post-exam instructions should be read carefully and followed.
Patients who experience any of these rare side effects should contact their doctor immediately:
- Severe abdominal pain
- Fever
- Bloody bowel movements
- Dizziness
- Weakness