Flexible Sigmoidoscopy

Flexible sigmoidoscopy is a procedure used to see inside the sigmoid colon and rectum. The flexible sigmoidoscope is a special camera, which can examine the left side of your large bowel and provide a lot of information to your physician.

Flexible sigmoidoscopy can detect inflamed tissue, abnormal growths, and ulcers. The procedure is used to look for early signs of cancer and can help doctors diagnose unexplained changes in bowel habits, abdominal pain, bleeding from the anus, and weight loss.

The sigmoid colon is the last one-third of the colon.

The colon comprises three main parts: the ascending colon, the transverse colon, and the sigmoid colon, sometimes called the descending colon. The colon absorbs nutrients and water and forms stool. The rectum is about 6 inches long and connects the sigmoid colon to the anus. Stool leaves the body through the anus. Muscles and nerves in the rectum and anus control bowel movements.

Sigmoidoscopy is performed to diagnose the cause of certain symptoms.

It is also used as a preventative measure to detect problems at an early stage, even before the patient recognizes symptoms. The following are some reasons for performing a sigmoidoscopy.

  • Bleeding:Rectal bleeding is very common. It often is caused by haemorrhoids or by a small tear at the anus, called a fissure. However, more serious problems can cause bleeding. Benign polyps can bleed. It is important to identify and remove polyps at an early stage before they can become cancerous. Rectal and colon cancers bleed and require immediate diagnosis and treatment. Finally, various forms of colitis and inflammation can cause bleeding.
  • Diarrhoea:Persistent diarrhoea should always be evaluated. There are many causes of diarrhoea and the exam is of great help in tracking down the specific cause.
  • Pain:Haemorrhoids and fissures are some causes of pain around the anus or in the rectum. Discomfort in the lower abdomen can be caused by tumours. Diverticulosis can occur in the lower bowel. With this condition, small pockets project from the bowel lining.
  • X-ray Findings:A barium enema X-ray exam may show abnormalities that need to be confirmed or treated by sigmoidoscopy.
  • Detection:Colon cancer is one of the most common cancers in the country.
  • It is highly curable if it is found early. This cancer usually begins in the colon as a polyp that remains benign for many years. Therefore, it is generally advisable to have a sigmoidoscopy after age 40 or 50. The tendency to develop colon cancer and polyps can be inherited.


Difference between Flexible Sigmoidoscopy and Colonoscopy

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, however, to prepare for and perform a flexible sigmoidoscopy usually requires less time.

The colon and rectum must be completely empty for flexible sigmoidoscopy to be thorough and safe, so the doctor will probably tell you to drink only clear liquids for 12 to 24 hours beforehand.

To prepare for a flexible sigmoidoscopy, one or more enemas are performed about 2 hours before the procedure to remove all solids from the sigmoid colon. An enema is performed by flushing water, laxative, or sometimes a mild soap solution into the anus using a special wash bottle.

In some cases, the entire gastrointestinal tract must be emptied by following a clear liquid diet for 1 to 3 days before the procedure, similar to the preparation for colonoscopy. Patients should not drink beverages containing red or purple dye.

Acceptable liquids include:

  • Fat-free bouillon or broth
  • Strained fruit juice
  • Water
  • Plain coffee
  • Plain tea
  • Sports drinks, such as Gatorade
  • Gelatin

A laxative or an enema may also be required the night before a flexible sigmoidoscopy. A laxative is medicine that loosens stool and increases bowel movements. Laxatives are usually swallowed in pill form or as a powder dissolved in water.

Patients should inform their doctor of all medical conditions and any medications, vitamins, or supplements taken regularly.

During a flexible sigmoidoscopy, patients lie on their left side on an examination table. The doctor inserts a long, flexible, lighted tube called a sigmoidoscope into the anus and slowly guides it through the rectum and into the sigmoid colon.

A small camera mounted on the scope transmits a video image from inside the colon to a computer screen, allowing the doctor to carefully examine the tissues lining the sigmoid colon and rectum.

Biopsy and Removal of Colon Polyps

The doctor can remove growths, called polyps, during flexible sigmoidoscopy using special tools passed through the scope. Polyps are common in adults and are usually harmless. However, most colon cancer begins as a polyp, so removing polyps early is an effective way to prevent cancer. If bleeding occurs, the doctor can usually stop it with an electrical probe or special medications passed through the scope.


A flexible sigmoidoscopy takes about 20 minutes. Cramping or bloating may occur during the first hour after the procedure. Bleeding and puncture of the large intestine are possible but uncommon complications. Discharge instructions should be carefully read and followed.

Patients who develop any of these rare side effects should contact their doctor immediately:

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


Flexible sigmoidoscopy and colonoscopy are very safe tests. Complications from flexible sigmoidoscopy are very rare. There is a slight risk of bleeding from the procedure. This risk is heightened in individuals whose blood does not clot well, either due to disease or medication, and in those with active inflammatory bowel disease. If a polyp is removed there can be bleeding; this usually settles but occasionally an operation may be required. During the examination the bowel is stretched by the instrument and although rare, it is possible for a puncture in the bowel wall to occur.

  • Mater Hospital
  • Sydney Adventist Hospital
  • Norwest Private Hospital
  • General Surgeons Australia
  • AMA