A flexible sigmoidoscopy can detect problems at an early stage

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A sigmoidoscopy is the visual examination of the inside of the rectum and sigmoid colon using a flexible fiberoptic or video endoscope. The colon is 5 to 6 feet long. During a sigmoidoscopy, only the last 1 to 2 feet of the colon is examined. This last part of the colon, just above the rectum, is called the sigmoid colon.

ColonoscopyReasons for the Exam

A sigmoidoscopy is performed to diagnose causes or symptoms or as a preventative measure to detect problems at an early stage before they are apparent to the patient.

  • Bleeding - Rectal bleeding is very common and is often caused by hemorrhoids or a small tear at the anus, called a fissure. Benign polyps, rectal and colon cancers and various forms of colitis and inflammation can cause bleeding.
  • Diarrhea
  • Pain - Hemorrhoids and fissures are some causes of pain around the anus or in the rectum. Discomfort can be caused by tumors or diverticulosis.
  • X-ray Findings - A barium enema x-ray may show abnormalities that need to be treated.
  • Diagnosing Cancer - Colon cancer is one of the most common cancers in the country and is highly curable if found early.


To receive the full benefits of the exam, the rectum and sigmoid colon must be clean. The patient is instructed on how to do this. This process involves drinking clear liquids or taking laxatives and enemas prior to the exam. The physician advises the patient regarding the use of regular medications during that time.


A flexible sigmoidoscopy is usually performed on an outpatient basis. It is performed with the patient lying on the left side with the legs drawn up. A sheet is placed over the lower body. A finger or digital exam of the anus and rectum is performed. The sigmoidoscope is then gently inserted into the rectum. Air is inflated into the bowel to distend it and allow for careful examination. The scope is advanced as far as possible without causing undue comfort. The exam usually takes 10 to 15 minutes although in some cases it may take longer. Sedation is usually required.

Alternative Testing

Barium enemas or other types of x-ray exams are alternative tests that allow a diagnosis to be made. Study of the stools can provide indirect information about a condition. Procedures, such as flexible sigmoidoscopies, allow direct viewing of the lower rectum and lower bowel which are by far the best way of examining this area.

Benefits of the Procedure

The benefit of a sigmoidoscopy is that a specific diagnosis can often be made. Conditions such as colitis can be monitored following treatment and polyps can be discovered at an early stage.

Side Effects and Risks

Bloating and distension usually occur for about an hour after the procedure until the air is expelled. Serious risks are uncommon. One such risk is excessive bleeding, especially with the removal of a large polyp. Due to mild sedation, the patient should not drive or operate machinery following the exam. For this reason, someone should be available to drive the patient home.