The colon helps your body absorb water and nutrients from the food you eat. It’s also where your stool is formed. The last third of your descending colon is called the sigmoid colon. It’s connected to the anus by the rectum. A colonoscopy helps your doctor examine the entire colon, but sometimes only the sigmoid colon warrants close inspection. That's when your doctor will recommend a sigmoidoscopy.
A sigmoidoscopy, also called a “flexible sigmoidoscopy,” is a procedure that lets your doctor look inside the sigmoid colon by using a flexible tube with a light on it. It helps your doctor check for:
- abnormal cells
Typically, pieces of tissue will be taken as samples to check for any abnormal cell changes.
You should tell your doctor if you notice:
- changes in your bowel habits
- rectal bleeding
- abdominal pain
- unexplained weight loss
These can be signs of various colon diseases, and a sigmoidoscopy might be the procedure to help determine the cause of your symptoms. A sigmoidoscopy is also a general screening tool for colon cancer.
Depending on your personal health history and whether your family has a history of colorectal cancers, you might need to have a sigmoidoscopy every five years after the age of 50.
Preparing for a sigmoidoscopy is similar to preparing for a colonoscopy. You’ll likely use one or more enemas approximately two hours before the procedure.
If your entire colon needs to be empty, you’ll need to prepare even more like you would for a colonoscopy. For example, you’ll follow a clear liquid diet for one to three days before the procedure. You may be given a powder laxative to mix with fluid to help empty your intestines. Liquids you can consume include:
- plain coffee or tea
- fat-free broth
- gelatin, like Jell-O
- sports drinks with electrolytes
You’ll want to avoid liquid with red or purple dye because it can look like blood in the colon.
Before the procedure, tell your doctor about any medical conditions you have and all medications and supplements you’re taking.
Your doctor will ask you to lie on your left side on an examination table. They'll insert a thin, flexible tube called a sigmoidoscope into your anus. The tube has a light and a very small camera on the end so images can be transmitted onto a monitor for your doctor to see. The tube will also inflate your colon with some air to make it easier to examine. You might be uncomfortable, but the procedure isn’t typically painful. Since you’re not usually under sedation during a sigmoidoscopy, your doctor might ask you to shift every so often to make it easier to move the scope.
If your doctor sees any polyps or growths, they might remove them. If there are any abnormal areas in the colon, small pieces of tissue might be removed for further examination.
The risks are minimal, but it’s possible for a tear to occur in the colon or the wall of the rectum on rare occasions. If your doctor takes a tissue sample, bleeding could occur in the place where the sample was taken.
The entire procedure takes 10 to 20 minutes. People can usually drive themselves to and from the appointment. If you’ve been given medication to calm or sedate you, you’ll need someone to drive you home afterward.
- severe abdominal pain
- bloody stool
Usually, some bloating or cramping is normal after the procedure. Call your doctor immediately if you have:
- severe abdominal pain
- bloody stool
These can be signs of something serious.
Your doctor will call you to discuss the results of any biopsies. If there’s a positive result that requires further testing, you may need to repeat the procedure. You may also need to repeat it if your doctor wasn’t able to get a good quality picture of your colon and rectum. Talk with your doctor about any questions or concerns regarding your colorectal health or the results.