Flexible Sigmoidoscopy

digestivesystemFlexible sigmoidoscopy is a procedure used by our Beverly Hills gastroenterologists to see the inside of the sigmoid colon and rectum. This 20 minute GI procedure allows doctors to begin the process of diagnosing disorders and problems in the final part of the body’s digestive tract.

A sigmoidoscope transmits a video image from inside the colon to a computer screen, and it allows our GI doctors to biopsy abnormal-looking tissues. Polyps can be removed using special tools that our doctors pass through the scope. If polyps or other abnormal tissues are found, the doctor may suggest examining the rest of the colon with a colonoscopy.

Flexible sigmoidoscopy can also detect inflamed tissue, abnormal growths, and ulcers. Additionally, the procedure helps our gastroenterologists diagnose unexplained changes in bowel habits, abdominal pain, bleeding from the anus, and weight loss.


Sigmoidoscopies are very similar to colonoscopies in that both view the colon, but flexible sigmoidoscopies do not view as much of the large intestine as a colonoscopy. They view the only the sigmoid colon (a.k.a. descending colon). The sigmoid colon is where most of the colorectal cancers develop. Our GI doctors can also remove polyps or take a biopsy during this procedure.

Flexible sigmoidoscopy enables the doctor to see only the sigmoid colon, whereas colonoscopy allows the doctor to see the entire colon. Colonoscopy is the preferred screening method for cancers of the colon and rectum, but a flexible sigmoidoscopy usually requires less time to prepare for and perform. That is why a doctor might schedule a flexible sigmoidoscopy, despite its limitations.


The colon (large intestine) absorbs nutrients and water and forms stool. The large intestine is broken down into four parts:

  • Ascending colon
  • Transverse colon
  • Descending colon
  • Sigmoid colon

The sigmoid colon is the last part of the large intestine (about 40 centimeters in length), and it connects to the rectum. About six inches in length itself, the rectum connects the sigmoid colon to the anus, where stool leaves the body. Nerves and muscles in both the rectum and anus control the body’s bowel movements.

Remember that flexible sigmoidoscopy only shows the doctor the sigmoid colon and rectum. As a result, a colonoscopy must be scheduled to see into those other parts of the colon if the doctor feels it is necessary.


All solids must be removed from the sigmoid colon prior to a flexible sigmoidoscopy. An enema (or two) is performed about two hours beforehand. (An enema involves the flushing of water, a laxative, or a mild soap solution into the anus using a special wash bottle to clear the gastrointestinal tract.)

Sometimes, the entire GI tract will need to be emptied before a flexible sigmoidoscopy. The patient would then follow a strict clear liquid diet for one day prior to the procedure. The clear liquids you can drink during this colon cleanse include:

  • Fat-free bouillon or broth
  • Gelatin
  • Plain coffee
  • Plain tea
  • Sports drinks (i.e. Gatorade)
  • Strained fruit juice
  • Water

Prior to the procedure, all patients need to inform their doctor of any medical conditions or medications/vitamins/supplements they take regularly. Generally speaking, patients should always let their doctors know about these things, but it is especially important prior to a flexible sigmoidoscopy.


During the exam, patients lie down on their left side atop an examination table. A thin, flexible tube (known as a sigmoidoscope) is inserted into the rectum. On the tip of the sigmoidoscope rests a tiny video camera that allows the gastroenterologist to see inside the rectum as well as most of the sigmoid colon.

The scope also inflates the colon with air, making it much easier to see. The small camera on the scope transmits video images from inside to a computer screen. All of this allows gastroenterologists to carefully examine the tissues lining the sigmoid colon and rectum as the GI doctor slowly guides it through. Patients may be asked to move every so often if the scope requires adjustments for better viewing.

When the sigmoidoscope passes completely through the sigmoid colon and reaches the transverse colon, it is carefully withdrawn. During this process, the lining of the colon is examined once again by the doctor.

Doctors can remove polyps (abnormal growths) during the procedure using special tools that can pass through the scope. Even though polyps are common in adults and usually benign (harmless), most colon cancer begins as a polyp. Therefore, removing polyps early on is an effective way to prevent the spread of cancer.

If bleeding were to occur in the sigmoid colon, a gastroenterologist most likely can stop it with an electrical probe or even special medications through the scope. Doctors can also take samples from abnormal-looking tissues for biopsy. Biopsies are tests in which doctors look for signs of disease on tissue under a microscope. Both tissue removal and attempts to stop intestinal bleeding are usually painless procedures. If polyps or other abnormal tissues are found, the doctor may suggest examining the rest of the colon with a colonoscopy.

Overall, the flexible sigmoidoscopy procedure lasts about 20 minutes. Minor side effects, like cramping or bloating, may occur during the first hour after the procedure. Bleeding and puncture of the large intestine can occur but they are uncommon complications. Patients that develop any of the following side effects should contact their doctor immediately:

  • Bloody bowel movements
  • Dizziness
  • Fever
  • Severe abdominal pain
  • Weakness


If you would like to schedule an appointment, contact our GI doctors today. You can reach us by phone at 855.360.9119 or by filling out the contact form in the upper right side of this page.

Next, read about Upper Endoscopy.