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Flexible Sigmoidoscopy (Flex Sig)

Procedure Summary

A flexible sigmoidoscopy, also known as a 'flex sig', is a procedure that allows the physician to visually exam a small portion of a patients large intestine known as the sigmoid colon. The physician will use an instrument called a colonoscope, a small diameter, flexible, lighted fiberoptic or video endoscope, for this brief procedure. This scope is inserted through the anus and is advanced approximately one to two feet into the sigmoid colon allowing the physician to visualize and capture pictures of any areas of concern. The colonoscope also has open channels that allow the physician to advance other instruments that may be needed to remove lesions, polyps, and take biopsies to aid in the diagnosis of any suspicious looking area. If the findings of the flex sig warrant further investigation, then a colonoscopy may be scheduled for further evaluation. A flex sig is usually performed as an outpatient exam and lasts from 5 to 15 minutes and requires no sedation.


The flexible endoscope is a remarkable piece of equipment that can be directed and moved around the bends in the lower colon and rectum. The image in the bowel is transmitted through the endoscope either to the eyepiece or a video screen. An open channel in the scope allows other instruments to be passed through it to take tissue samples (biopsies) or to remove polyps.

Reasons for the Exam

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:


Rectal bleeding is very common. It is often caused by hemorrhoids 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.


Persistent diarrhea should always be evaluated. There are many causes of diarrhea and the exam is of great help in tracking down the specific cause.


Hemorrhoids and fissures are some causes of pain around the anus or in the rectum. Discomfort in the lower abdomen can be caused by tumors. Diverticulosis can occur in the lower bowel. With this condition, small pockets or sacks project from the bowel.

X-ray Findings

A barium enema x-ray exam may show abnormalities that need to be confirmed or treated by sigmoidoscopy.


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. If parents, brothers, or sisters have had colon polyps or colon cancer, it is even more critical to have this exam. The tendency to develop colon cancer and polyps can be inherited.


A patient having a flex sig needs to be clean from stool which is achieved by the patient being on a CLEAR LIQUID DIET the day before the procedure beginning with breakfast. Your physician may prescribe additional preps to assist with the cleansing of the colon. Please see your physician for further instructions regarding the use of regular medications the day before and the day of your procedure. Because this procedure does not usually require sedation, it is not necessary to have someone drive you to and from the center.


Flexible sigmoidoscopy is usually performed on an outpatient basis. It is performed with a 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. Then the endoscope is gently inserted into the rectum. Air is inflated into the bowel to expand it and allow for careful examination. The patient usually feels a slight discomfort similar to strong gas cramps. The endoscope is then advanced under direct vision and moved around the various bends in the lower bowel.

It is advanced as far as possible without causing undue discomfort. When possible, the exam is continued to 25 inches (60 cm). Certain conditions, such as diverticulosis, irritable bowel syndrome, or prior pelvic surgery may produce discomfort when the sigmoid colon is entered by the endoscope. The exam is stopped if this occurs. The exam usually takes 5 to 15 minutes. Sedation is not normally required.


The benefits of sigmoidoscopy can include the following:

It is often possible to determine the specific cause of symptoms.

Conditions such as colitis and diverticulosis can be monitored to determine effectiveness of treatment.

Polyps and tumors can be discovered at an early stage.


Alternative testing includes barium enema x-ray exams. Additionally, the stools can be examined in a variety of ways to uncover or study certain bowel conditions. However, a direct look at the lower rectum and the lower bowel by sigmoidoscopy is by far the best method of examining this area.

Side Effects and Risks

Bloating and bowel distension are common due to the air inflated into the bowel. This usually lasts only 30 to 60 minutes. If biopsies are done or a polyp is removed, there may be some spotting of blood. However, this is rarely serious. Other uncommon risks include a diagnostic error or oversight, or a tear (perforation) of the wall of the colon which might require surgery.

When to Expect Results

The physician performing the procedure will speak with you and a family member or person(s) that has been given written permission for disclosure of your results. Following the exam in the recovery room, the physician will give you the results of the exam and advise you on further treatment or follow up should any be necessary. In the event that the physician removed a polyp or a biopsy(s) was taken, then you will be advised on when you can expect to receive these results. A pathologist will review the biopsy, and the results are usually available in ten days.


Sigmoidoscopy is a simple outpatient exam which can uncover a serious medical problem. Specific diagnoses can be made. Treatment programs can be evaluated, or reassurance can be provided when the exam is normal. It is one of the most useful and simple exams in medicine.

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