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Flexible Sigmoidoscopy - Risks, Procedure and Results

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A flexible sigmoidoscopy helps in visualizing the lower part of the colon. This article gives a detailed view of flexible sigmoidoscopy.

Written by

Dr. P. Saranya

Medically reviewed by

Dr. Ghulam Fareed

Published At January 13, 2023
Reviewed AtJuly 5, 2023


A flexible sigmoidoscopy is a procedure to evaluate the lower part of the colon. Sigmoidoscopy uses a thin, flexible tube which is inserted into the rectum during flexible sigmoidoscopy. This is attached with a video camera which allows viewing of the rectum, sigmoid colon, and most of the descending colon. Flexible sigmoidoscopy is a minimally invasive procedure, in which a flexible endoscope is used. A rigid endoscope is used in rigid sigmoidoscopy.

Why Is Flexible Sigmoidoscopy Done?

Investigation: Flexible sigmoidoscopy's done to investigate the causes of intestinal signs and symptoms, including abdominal pain, bleeding in the rectum, change in bowel habits, and other intestinal problems.

Screening: Flexible sigmoidoscopy is one option for screening colon cancer. Suppose the patient is at average risk for colon cancer, which means the patient's age is 50 or older and has no other risk factors other than age. In that case, the doctor suggests a flexible sigmoidoscopy procedure every five years to screen for colon cancer.

Sigmoidoscopy may be preferred over colonoscopy because the preparation and the procedure take less time than colonoscopy, and anesthesia is not required. There is a lower risk of colon or rectal wall perforation with sigmoidoscopy than with colonoscopy.

What Are the Risks of Flexible Sigmoidoscopy?

A flexible sigmoidoscopy procedure possesses some risks.

They include:

  • Perforation of the rectum or colon wall.

  • Bleeding from the biopsy site where a tissue sample was taken.

  • Pain in the abdomen.

How to Prepare Before a Flexible Sigmoidoscopy Procedure?

Before the flexible sigmoidoscopy, it is essential to empty the colon because residues present can obscure the view of the colon and rectum during the examination.

The following are to be done:

  • Special Diet Before the Procedure: Avoid solid food the day before the procedure. Only clear liquids are advised - plain water, tea, and coffee without milk or cream and carbonated beverages. Avoid red-colored liquids as they may confuse with blood during the procedure. The patient is advised not to eat or drink anything after midnight.

  • Laxative: The doctor recommends a laxative either in pill or liquid form. A laxative is taken the night before the procedure.

  • Enema: Over-the-counter enema kit is given a few hours before the procedure to empty the colon. The doctor advises taking two enemas.

  • Medications: Inform the doctor about the medicines you are taking a week before the procedure, such as medications for diabetes, iron supplements, allergy to medicines, and blood thinners like Aspirin, Warfarin, and Clopidogrel. Inform the medical conditions such as pregnancy, heart problems, and lung issues.

What Happens During Flexible Sigmoidoscopy?

During the procedure, the patient wears a gown and is asked to lie on the left side of the table with knees bent towards the abdomen. The doctor then inserts a thin, flexible sigmoidoscope into the rectum.

The sigmoidoscope contains light and a tube. The doctor inflates air into the tube, which expands the colon, allowing a better view of the colon. When the scope is moved in the intestine, the patient may have abdominal cramping or an urge to have. Mild cramping during the procedure is relieved by taking several slow deaths.

The sigmoidoscope contains a tiny camera in the end which helps to view the inside of the colon. The doctor can insert instruments into the tube through which tissue samples are taken. The sigmoidoscope is slowly removed from the colon after the procedure. The procedure typically takes about 15 minutes. Anesthesia and pain medications are not necessary. The doctor recommends a colonoscopy to view the entire colon length if a polyp is found.

What Happens After the Procedure?

After the procedure, the patient feels mild abdominal cramping. Walking after the procedure may relieve discomfort. A small amount of blood is seen in bowel movements after the procedure, which is normal. The patient can drink and eat normally.

What Is the Result of Flexible Sigmoidoscopy?

The doctor reviews the results of the procedure and discusses the results with the patient.

The result can be positive or negative.

Negative Result: The result of a flexible sigmoidoscopy procedure is negative if the doctor does not find any abnormalities in the colon. Suppose the patient is at average risk for colon cancer, which means the patient's age is 50 or older, and there are no risk factors other than age. In that case, the doctor suggests a flexible sigmoidoscopy procedure after five years.

Positive Result: The result of a flexible sigmoidoscopy procedure is positive if the doctor finds any polyps or abnormalities in the colon. Based on the findings, a colonoscopy is recommended to examine the abnormalities thoroughly and to view the entire length of the colon.

What Is the Difference Between Sigmoidoscopy and Colonoscopy?

A colonoscopy is another test used to view changes or abnormalities in the colon. Colonoscopy is a procedure performed to detect the presence of colorectal cancers. A colonoscopy uses a thin, flexible tube with a tiny camera at the end, to view the entire colon. It is the longest of all scopes reaching the whole colon length, whereas the flexible sigmoidoscope can view the lower part of the colon.

How Is It Different From Rigid Sigmoidoscopy?

Rigid sigmoidoscopy, also known as proctoscopy, is used to detect rectum and anus abnormalities. Proctoscope are made up of a rigid tube, whereas a flexible sigmoidoscope comprises a thin, flexible tube.


Flexible sigmoidoscopy is a safe and effective procedure to view the problems of the rectum and lower part of the colon. The procedure is simple and tolerable.

Frequently Asked Questions


How Intense Is the Pain During Flexible Sigmoidoscopy?

A flexible sigmoidoscopy is usually not painful. However, it may cause slight discomfort. A slight pinch might be experienced if the tissue is removed for biopsy. Deep breaths during tube insertion help decrease the pain.


How Can We Differentiate Between a Flexible Sigmoidoscopy and a Colonoscopy?

A flexible sigmoidoscopy is less invasive than a colonoscopy as it only examines the lower part of the colon since a colonoscopy examines the entire large intestine. A sigmoidoscopy involves the sigmoid part of the colon, whereas, in a colonoscopy, the entire colon is examined for any abnormality and requires a long tube or scope.


Is it Required to Sleep or Sedate the Patients During Flexible Sigmoidoscopy?

A flexible sigmoidoscopy usually takes around 10 to 20 minutes. Sleep and sedation are usually not required during the procedure. If biopsies are required, the procedure might take a bit longer, but it still does not need sedation or any medication for pain.


How Much Time Is Taken for a Flexible Sigmoidoscopy Procedure?

A flexible sigmoidoscopy examination usually takes about 15 minutes and can take a little longer if biopsies are required. A trained medical professional performs the diagnostic procedure in a hospital or a clinic.


Does Flexible Sigmoidoscopy Cause More Pain Than a Colonoscopy?

Flexible sigmoidoscopy can cause more discomfort than a colonoscopy. However, it is usually well tolerated and does not cause any significant pain. Flexible sigmoidoscopy can cause more discomfort in women than in men.


How Does the Patient Feel After a Flexible Sigmoidoscopy?

The patient might feel cramping, belly pain, or abdominal bloating during the first hour after the examination. The patient usually feels better after the passage of gas. The patient can get back to their regular routine right after the procedure.


What Is the Depth of Flexible Sigmoidoscopy?

The depth of flexible sigmoidoscopy is usually around 50 centimeters or the last two feet of the large intestine. A tiny video camera at the tip of the tube helps the doctor view the inside of the sigmoid colon and part of the descending colon.


Can the Patient Eat the Night Before and on the Day of the Flexible Sigmoidoscopy Procedure?

The doctor advises the patient not to eat the day before the procedure. The patients may consume clear liquids like plain water, tea, and coffee without milk. If the patient is taking a specific medication, the doctor might recommend changes in the dosage or stop the medication temporarily.


Is an Enema Required Before Flexible Sigmoidoscopy?

A flexible sigmoidoscopy usually requires enemas before the procedure to clean the lower portion of the colon. If the travel time is more than two hours, The doctor might schedule an early appointment to prepare for the enema.


Can Diverticulitis, Ulcerative Colitis, and Chron’s Disease Be Detected Through a Flexible Sigmoidoscopy?

Yes, a flexible sigmoidoscopy exam can be used to diagnose diverticulitis since the most common location for diverticulitis is the sigmoid colon. It also helps diagnose ulcerative colitis and Crohn's disease, which involves the lower part of the colon.


What Is the Accuracy of Flexible Sigmoidoscopy?

Flexible sigmoidoscopy can diagnose 70 % of cancers and polyps. However, it cannot detect 40 % of proximal neoplasms that do not involve a distal lesion. It is an accurate and effective diagnostic tool for screening colorectal cancer in men and young women.

Dr. Ghulam Fareed
Dr. Ghulam Fareed

Medical Gastroenterology


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