Sigmoidoscopy is the visual examination of the inside of the rectum and lower part of the colon, called the sigmoid colon. The examination is done using an endoscopy which is a lighted, flexible tube connected to a video screen. During a sigmoidoscopy only the last one to two feet of the five to six-foot-long colon (large intestine) is examined.
An endoscope is a flexible tube with a tiny, optically sensitive computer chip at the end that can easily be moved around the bends in the lower colon and rectum. As the physician moves the endoscope through the bowel, the image is transmitted to 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.
Sigmoidoscopy is performed to diagnose the cause of certain symptoms, including:
- Bleeding: Rectal bleeding is very common. It often is caused by hemorrhoids or by a small tear at the anus, called a fissure. However, more serious problems can also cause bleeding, including benign polyps. 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. Various forms of colitis and inflammation also can cause bleeding.
- Diarrhea: Persistent diarrhea should always be evaluated. There are many causes of diarrhea, and this procedure is effective in tracking down the specific cause.
- Pain: Hemorrhoids and fissures can cause pain around the anus or in the rectum. Discomfort in the lower abdomen can be caused by tumors. Also, diverticulosis can cause pain in the lower bowel.
- X-ray findings: A barium enema X-ray exam may show abnormalities that need to be confirmed or treated by sigmoidoscopy.
Yes. With a sigmoidoscopy, conditions such as colitis and diverticulosis can be monitored to determine the effectiveness of treatment. Sigmoidoscopy is also used as a preventive measure to detect problems at an early stage, such as polyps and tumors, even before you have symptoms. It can also help detect colon cancer, although a colonoscopy is considered the best way to examine the entire colon.
Yes. To obtain the full benefit of the exam and allow a thorough inspection, the rectum and sigmoid colon must be clean. Preparation usually involves drinking clear liquids the day before the procedure, along with taking enemas and/or laxatives. Your physician will give you specific instructions.
Flexible sigmoidoscopy is usually performed on an outpatient basis. Your physician will ask you to lie on your left side with your legs drawn up, and will place a sheet over your lower body. He or she will begin by performing a digital exam of the anus and rectum. Next, the endoscope is gently inserted. The bowel is inflated with air to expand it and allow for careful examination. You may feel a slight discomfort similar to strong gas cramps. The endoscope is advanced and moved as far as possible without causing you discomfort around the various bends in the lower bowel. Certain conditions, such as diverticulosis, irritable bowel syndrome or prior pelvic surgery may produce discomfort when the sigmoid colon is entered by the endoscope. Your physician will stop the exam if this occurs. The exam usually takes 5 to 15 minutes. Normally, sedation is not required.
Bloating and bowel distension are common. This usually lasts only 30 to 60 minutes. If biopsies are done or if a polyp is removed, there may be some spotting of blood. However, this is rarely serious. Uncommon risks include a diagnostic error or oversight or a tear of the wall of the colon, which might require surgery.
Alternative testing includes a barium enema X-ray. In addition, 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 lower bowel by sigmoidoscopy is the best method of examining this area.