Sigmoidoscopy vs Colonoscopy - Understand the Difference

Medically Reviewed by Dr. Aman Priya Khanna
Written by Nikita Tyagi, last updated on 18 January 2023| min read
Sigmoidoscopy vs Colonoscopy - Understand the Difference

Quick Summary

  • Sigmoidoscopy and colonoscopy are both procedures used to examine the large intestine.
  • A colonoscopy examines the entire large intestine, while a sigmoidoscopy only diagnoses the sigmoid colon.
  • Risk factors for both procedures include age, family history of colon cancer, and personal history of polyps or colorectal cancer.

Have you ever undergone a sigmoidoscopy or a colonoscopy? Or have you been prescribed one of them but are confused between both? A colonoscopy examines the entire large intestine, while a sigmoidoscopy only diagnoses the sigmoid colon. If you want to learn about colonoscopy and sigmoidoscopy in detail, you have come to the right place! This article will highlight everything you need to know about a sigmoidoscopy vs colonoscopy. 

We shall also highlight the difference between the two. So keep reading this article to find out! Apart from sigmoidoscopy vs colonoscopy, learn the definition, risk factors, and types of colonoscopy and sigmoidoscopy.

What is a Sigmoidoscopy?

A sigmoidoscopy is a medical screening test by which a healthcare specialist checks the lower part of the large intestine, known as the sigmoid colon. The sigmoid colon is located near the rectum and anus. The entire sigmoidoscopy procedure usually takes 15 to 30 minutes. 

Based on the sigmoidoscope, sigmoidoscopies generally are of two types:

  1. Flexible Sigmoidoscopy: This sigmoidoscopy can examine about 60 cm of the colon. 
  2. Rigid Sigmoidoscopy: This sigmoidoscopy examines the colon only up to 25 cm. 

During the sigmoidectomy, the healthcare specialist performs the following steps:

  1. Firstly, the patient will be made to lie on their left side with their knees pulled up to their chest. The healthcare specialist will then dilate or enlarge the patient’s anus. 
  2. The healthcare specialist then puts a lubricated tube and advances slowly through the rectum and lower colon.
  3. With the help of a tiny video camera, the healthcare specialist checks for any abnormalities in the lower part of the colon. If there is any abnormal growth, such as colon polyps, the healthcare specialist may remove it through the extension attached to the sigmoidoscope. The patient may bleed during this procedure.
  4. After excision of the abnormal growth, the tube is slowly removed from the patient’s anus. 
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Advantages and Disadvantages of Sigmoidoscopy

Sigmoidoscopy is generally considered a safe and well-tolerated procedure. However, as with any medical procedure, there are some pros and cons.

The following are the advantages of a sigmoidoscopy:

  1. Less or no pain during the process.
  2. No need for sedation during a sigmoidoscopy.
  3. Sigmoidoscopy takes less time than a colonoscopy.
  4. The side effects of sigmoidoscopy are less than a colonoscopy, as it only invades the lower part of the colon. 

The following are the disadvantages of a sigmoidoscopy:

  1. The patient might bleed excessively during the biopsy procedure.
  2. The patient’s gastrointestinal lining may get inflamed.
  3. The walls of the intestine may get perforated.
  4. A sigmoidoscopy isn’t as accurate as a colonoscopy for detecting colorectal cancer. 

What is a Colonoscopy?

A colonoscopy is a procedure in which the healthcare specialist checks the colon and rectum of the patient using a tube known as a colonoscope. 

The colonoscope has a tiny video camera, which provides a clear view of a person’s colon and rectum. The doctors check the video to diagnose any disease or abnormalities of the colon or rectum. This procedure generally takes about 30 to 60 minutes to complete.

Based on for what purpose the colonoscopy is being used, it is of two types. 

  1. Screening Colonoscopy: A colonoscopy that is performed as a screening test to rule out disease, even when no symptoms present. This is done as a preventive measure. 
  2. Diagnostic Colonoscopy: A colonoscopy is performed to diagnose a disease after seeing its symptoms.

During the colonoscopy procedure, the healthcare specialist follows the following steps:

  1. In a colonoscopy test, the patient is made to lie on their left side with their knees pulled up to their chest.
  2. Then a lubricated tube, referred to as a colonoscope, is slowly inserted into the patient's large intestine through the anal opening, and air may be introduced to help open up the colon. 
  3. As the colonoscope has a tiny video camera, the healthcare provider tries detecting any abnormalities in the patient’s large intestine with its help. The healthcare provider may inject air into the patient’s colon to make it look clear. 
  4. If the healthcare provider finds any foreign growth inside the patient’s intestine, he/ she may perform a biopsy to remove it. 
  5. During the biopsy, the patient may bleed. However, it is normal, and there’s no need to worry about it. 
  6. Once the abnormal growth is removed, the tube is slowly removed from the patient’s anus. 

Advantages and Disadvantages of Colonoscopy

Colonoscopy is generally considered a safe and well-tolerated procedure. However, it is common to have pros and cons associated with the procedure. Below mentioned are some of the advantages and disadvantages of colonoscopy.

These are the following advantages of a colonoscopy:

  1. It accurately detects colorectal cancer. 
  2. The test examines the whole intestine.
  3. Anomalous growth, such as polyps, can easily be removed during a colonoscopy.
  4. It helps to detect diverticulitis and colitis as well. 

These are the following disadvantages of a colonoscopy:

  1. The test may take an hour. 
  2. The sedation, which is used for the process, may react and cause complications. 
  3. The patient may bleed heavily during the biopsy.
  4. The intestinal wall may get perforated. 
  5. The patient may also catch a bacterial infection.

Difference Between Sigmoidoscopy and Colonoscopy

Colonoscopy and sigmoidoscopy are both a type of endoscopy. Moreover, both of them target the same area, i.e. the colon. However, the difference between sigmoidoscopy vs colonoscopy lies in the fact that sigmoidoscopy only targets the lower part of the colon. In contrast, a colonoscopy gives a complete look at the large intestine along with the rectum. Keep reading to learn everything about the difference between sigmoidoscopy vs colonoscopy. 


Sigmoidoscopy Colonoscopy

Area of Examination

Lower part of the colon

The entire large intestine

The instrument used

A shorter, flexible tube with a camera on the end, called a sigmoidoscope, which is inserted through the rectum and advanced through the sigmoid colon and rectum.

A long, flexible tube with a small camera on the end called a colonoscope, which is inserted through the rectum and advanced through the entire colon.

Ideal candidates

Sigmoidoscopy is recommended to people: 

  1. Aged above 50 years or have family history of colon cancer/polyps
  2. With constipation
  3. With polyps (abnormal growths)
  4. With diarrhea
  5. With belly pain
  6. With bleeding

Colonoscopy is recommended to people:

  1. At the risk of colorectal cancer
  2. With Familial Adenomatous Polyposis (FAP).  
  3. With lynch syndrome.
  4. With inflammatory bowel disease.
Effectiveness Talking about the sigmoidoscopy effectiveness, a sigmoidoscopy may miss out on certain medical issues, such as colorectal cancer. Hence, it is less effective than a colonoscopy. Between sigmoidoscopy vs colonoscopy, a colonoscopy is more effective in diagnosing colorectal cancer and other diseases than a sigmoidoscopy.

A sigmoidoscopy has the following risks:

  1. Perforation of the intestine
  2. Excess bleeding post-biopsy. 
  3. Inflammation in the lining of the stomach

However, a sigmoidoscopy is safer than a colonoscopy. 

A colonoscopy has the following risks: 

  1. Perforation in the colon/ large intestine
  2. Uncontrolled bleeding
  3. Infection

Between sigmoidoscopy vs colonoscopy, a colonoscopy is riskier than a sigmoidoscopy. 

Time requirement

Usually takes 15 to 30 minutes. 

A colonoscopy may take up to 30 to 60 minutes. 

Recovery time

Shorter recovery time, as the procedure is less invasive

Longer recovery time.

Prices in India 

₹3,000 to ₹10,000

₹9,000 to ₹22,000.

These were some of the common difference between sigmoidoscopy and colonoscopy. However, one should note that every medical test has its pros and cons. Colonoscopy and sigmoidoscopy are no exceptions. With that said, people should only undergo the test their healthcare provider suggests.

When to Consult a Doctor for Colonoscopy and Sigmoidoscopy

It is generally recommended to consult a doctor if you have symptoms such as persistent constipation, diarrhoea, rectal bleeding, abdominal pain or discomfort, or if you have a family history of colon cancer. It is also recommended to consult a doctor if you are over 50 years old.

  1. For a sigmoidoscopy, it is recommended to have a screening every 5 years starting at age 50. 
  2. For colonoscopy, it is recommended to have a screening every 10 years starting at age 50, or earlier if you have a family history of colon cancer or other risk factors.

If you have been experiencing any symptoms or if you are over 50 years old and haven't had a colon cancer screening yet, it's important to talk to your doctor about your options. They will be able to advise you on whether a sigmoidoscopy or colonoscopy would be appropriate for you and when you should schedule it.


A colonoscopy is a more effective medical examination for diagnosing colon diseases. A sigmoidoscopy procedure often misses out on illnesses easily detectable through a colonoscopy. However, sigmoidoscopy has its benefits. For instance, it carries lesser risks than a colonoscopy. 

If you’re confused between sigmoidoscopy vs colonoscopy or don’t know which is better for you, consider talking to a healthcare provider. You can also speak to our expert team of experienced doctors at HexaHealth to learn the difference between sigmoidoscopy and colonoscopy. We also provide top-notch colonoscopy and sigmoidoscopy medical tests. Plus, we make sure that you don’t have to suffer pain or discomfort during the entire process. Get on a FREE consultation call to learn more about colonoscopy vs sigmoidoscopy.

Frequently Asked Questions

No, sigmoidoscopy is not the same as colonoscopy. A sigmoidoscopy only diagnoses the lower part of the colon. Meanwhile, a colonoscopy examines the entire large intestine.

Yes, a sigmoidoscopy is safer than a colonoscopy. The reason being a sigmoidoscopy is less penetrative. Therefore, there is a reduced risk of the colon getting perforated, developing an infection, or bleeding. 

If you have developed a problem in the sigmoid colon, your doctor may recommend a sigmoidoscopy. However, if the doctor finds abnormal growth, such as colon polyps, during the sigmoidoscopy, you might also need to undergo a colonoscopy. Moreover, healthcare providers often recommend colonoscopy more than sigmoidoscopy, as it provides a bigger picture of the colon.

Colonoscopies are better than sigmoidoscopies because they:

  1. Provide a better view of the large intestine. 
  2. Are more efficient in reducing colon cancer mortality rate.
  3. Detect colon cancer easily. 
Yes, a sigmoidoscopy is an effective medical test. It has been found to reduce the colorectal cancer developing rate by 18–26% and the colorectal cancer mortality rate by 22–31%.

When a sigmoidoscopy finds polyps, it is more likely that the polyps might also be present in other parts of the large intestine. As a result, a colonoscopy is conducted after a sigmoidoscopy to detect colon polyps further. 

The difference between rigid sigmoidoscopy and flexible sigmoidoscopy is that rigid sigmoidoscopy can only examine the colon up to 25 cm. While the flexible sigmoidoscopy examines the colon up to 60 cm. 

Both colonoscopy vs sigmoidoscopy has their risks. The risks involved with a sigmoidoscopy are that it can cause excess bleeding and even perforation of the colon. It can also miss detecting certain diseases. While a colonoscopy can cause bleeding, infection, and perforation of the large intestine. 

Updated on : 18 January 2023

Disclaimer: The information provided here is for educational and learning purposes only. It doesn't cover every medical condition and might not be relevant to your personal situation. This information isn't medical advice, isn't meant for diagnosing any condition, and shouldn't replace talking to a certified medical or healthcare professional.


Dr. Aman Priya Khanna

Dr. Aman Priya Khanna

MBBS, DNB General Surgery, Fellowship in Minimal Access Surgery, FIAGES

12 Years Experience

Dr Aman Priya Khanna is a well-known General Surgeon, Proctologist and Bariatric Surgeon currently associated with HealthFort Clinic, Health First Multispecialty Clinic in Delhi. He has 12 years of experience in General Surgery and worke...View More


Nikita Tyagi

Nikita Tyagi

BPharm (Jawaharlal Nehru Technical University, Hyderabad)

2 Years Experience

An enthusiastic writer with an eye for details and medical correctness. An avid reviewer and publisher. She emphasises authentic information and creates value for the readers. Earlier, she was involved in making ...View More

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