Flexible sigmoidoscopy: what is it about?

Flexible sigmoidoscopy is minimally invasive, being especially useful for the early diagnosis of colorectal cancer. Here we show you more.

Last update: February 15, 2022

Flexible sigmoidoscopy is a minimally invasive medical procedure in which a camera endoscope is inserted through the rectum. This allows the end of the colon to be seen.

In this way pathologies of the anus, rectum and the final portion of the large intestine are studied. It is of special importance in the early diagnosis of colorectal cancer and in the identification of intestinal polyps.

Sigmoidoscopy can be rigid or flexible, depending on the probe used. Flexible sigmoidoscopy is now used more frequently, as it allows bending to the shape of the large intestine.

The fundamental difference with a colonoscopy is that the sigmoidoscopy is less invasive.

Why is a flexible sigmoidoscopy performed?

Flexible sigmoidoscopy allows visualization of the anus, rectum, and sigmoid colon. It is useful in the diagnosis of gastrointestinal pathologies, to define the origin of lower gastrointestinal bleeding, for the early diagnosis of colorectal cancer and the identification of masses (polyps or tumors).

In the early diagnosis of colorectal cancer, it becomes relevant among people with risk factors and in people older than 50 years. For this last group, its periodic performance every 5 years is proposed, although colonoscopy may be preferred.



Why colonoscopy before sigmoidoscopy in prevention?

Colonoscopy is generally preferred for early diagnosis of colorectal cancer because it allows visualization of the large intestine in its entirety. However, sometimes sigmoidoscopy can be chosen, considering the following advantages:

  • Preparation is less.
  • It does not require anesthetics.
  • The procedure is shorter.
  • Complications from direct damage to the colon are less common.
Colon cancer is a frequent oncological pathology. Its early detection improves the prognosis.

How is flexible sigmoidoscopy performed?

Flexible sigmoidoscopy is a minimally invasive procedure that performed on an outpatient basis. It does not usually require sedation and lasts less than 1 hour.

It begins by placing the person lying on the stretcher on their left side with their legs bent. An inspection of the perianal region is then performed, followed by digital rectal examination.

The endoscopic probe is then inserted at its tip it has a camera and a light source, therefore, it allows evidence of erosive lesions, polyps, tumors and sources of bleeding, among others. In addition, it works as a treatment, by allowing lesions to be resected, biopsies to be taken or bleeding points to be cauterized. Recovery is immediate.

What risks does it have?

Due to intestinal stimulation, it can cause pain, abdominal distension, colic and gas sensation that disappear after hours. Occasionally there may be bleeding especially if a polyp was removed or a biopsy sample was obtained.

The most serious and rare complications are the following:

  • Direct damage to colonic tissue.
  • Accidental perforation of the intestine.

How should the preparation be?

First of all, you should alert your doctor if you are pregnant, if you have any heart or lung condition, if you are allergic or have any disease that affects blood clotting. What’s more, It should be indicated if any medication is taken.

On the other hand, complete bowel lavage is not required, but emptying of the final part of the large intestine is recommended before flexible sigmoidoscopy. This can be done with the use of an enema or glycerin suppositories. It is recommended to place them between 2 to 4 hours before the procedure.

However, you do have to refrain from consuming solids or liquids for the previous 6 hours. In case of taking medications for arterial hypertension, the thyroid gland or glucose regulation, it is recommended to space them up to 2 hours before the start of the study.

The examination method with sigmoidoscopy is less invasive and does not usually require sedation, compared to colonoscopy.


Its main use is preventive.

The greatest utility of the study is screening for colorectal cancer. Especially in cases of family history of polyposis. If there were, the first step is genetic testing. Subsequently, periodic evaluations are made for screening.

Flexible sigmoidoscopy is considered to be of special importance in the diagnosis and treatment of pathologies of the colon. Even so, its limitation is that it does not evaluate the entire intestine, which leaves out 30% of cancers in the area.

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