What is Flexible Sigmoidoscopy?

Sigmoidoscopy is the visual examination of the inside of the rectum and sigmoid colon using a lighted, flexible, fiberoptic endoscope. The colon, or large intestine, is 5-6 feet long. During a sigmoidoscopy, only the last 1-2 feet of the colon is examined. This last part of the colon, just above the rectum, is called the sigmoid colon. Equipment

ColonThe flexible endoscope is a remarkable piece of equipment that can be directed and moved around the bends in the lower colon and rectum. A thin, glass fiberoptic bundle collects light in the end of the scope and, regardless of how it is angled, transmits the image to the physician's viewing end. An open channel in the scope allows other instruments to be passed through it to perform biopsies or remove polyps.


Reasons for the Exam

Sigmoidoscopy is performed because of symptoms or to detect problems at an early stage before they are apparent to the patient.

Bleeding-Rectal bleeding is very common. It often is caused by hemorrhoids or 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 become malignant. Rectal and colon cancer bleed and require immediate diagnosis and treatment. Finally, various forms of colitis and inflammation can cause bleeding.

Diarrhea-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.

Pain-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, as well as pockets along the sigmoid colon, called diverticulosis.

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 may begin in the colon as a polyp that remains benign for many years. Therefore, it is advisable to have a surveillance exam after a certain age. If there is a history of colon polyps or cancer in parents or siblings, it is even more critical to have this exam because there is a definite hereditary aspect for colon cancer.



 To obtain the full benefits of the exam, the rectum and sigmoid colon must be clean to allow thorough inspection. Preparation usually involves oral liquids the day before or at supper the night before, along with enemas and/or laxatives. Specific instructions for preparation are always given by the physician's office.

See the "Procedure Preperation" section of the website.


The Procedure

Sigmoidoscopy is performed on an outpatient basis. It is performed with the patient lying on the left side with the right leg drawn up. A sheet is placed over the lower body. A finger or digital exam of the anus and rectum is performed. Then the sigmoidoscope is gently inserted into the rectum. Air is inflated into the bowel to distend it and allow for careful examination. The patient will usually feel this distension of the rectum. The scope is then advanced under direct vision moving around the various bends in the lower bowel.

The scope is advanced as far as possible without causing undue discomfort. When possible, the exam is continued to 60 cm (25 inches). Certain conditions, such as diverticulosis, irritable bowel syndrome or prior pelvic surgery, may produce discomfort when the sigmoid colon is entered. The exam is stopped if this occurs. The entire exam usually takes only 5-10 minutes. Sedation usually is not required.



The benefits of sigmoidoscopy are considerable. A specific diagnosis can often be made. A condition, such as colitis, can be monitored following treatment. Polyps and tumors can be discovered at an early stage.


Side Effects and Risks

Bloating and bowel distension are common due to the air inflated into the bowel. This usually lasts only 30-60 minutes. If biopsies are done or if a polyp is removed, there may be some spotting of blood. This is rarely ever serious. One extremely rare risk is a perforation or tear of the sigmoid colon.


In Summary

Sigmoidoscopy is a simple outpatient exam that provides the physician with a great deal of useful information. Specific diagnosis 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. The physician can answer any questions the patient may have.