Colonoscopy

What is colonoscopy

Colonoscopy is the endoscopic examination of the large intestine (colon) and, when needed, the lower part of the small intestine, known as the terminal ileum.

It allows direct inspection of the lining of the bowel, targeted biopsies and, in the same session, the removal of lesions. With the latest generation of endoscopes and the support of artificial intelligence, lesions can be detected with great accuracy, even at early stages.

It is not only a diagnostic examination. It is the only examination that prevents colorectal cancer, by removing polyps before they have a chance to progress.

When is colonoscopy needed

The examination is recommended both to investigate symptoms and for screening in people without any complaints. The main indications are:

• Screening from the age of 45, regardless of gender, for people at average risk
• Blood in the stool or a positive fecal hemoglobin test
• A persistent change in bowel habits, such as diarrhea or constipation
• Iron deficiency anemia with no explanation
• Unexplained weight loss, persistent abdominal pain
• Persistent bloating
• A family history of colorectal cancer or polyps, in which case screening starts earlier
• Follow-up after polyp removal, as well as investigation and follow-up of inflammatory bowel disease

With or without sedation?

This is the question patients ask most often, and the answer is not the same for everyone.

With sedation. The examination is usually performed after intravenous sedative medication, with continuous monitoring of heart and breathing. The patient feels no pain and usually does not remember the procedure. Beyond comfort, sedation also has a diagnostic benefit: a relaxed patient allows a slower and more careful inspection, and therefore a better detection rate.

Without sedation. It is possible, and some patients tolerate it well, especially when the examination is a simple diagnostic one. It is chosen when the patient prefers it, needs to drive afterwards, or when there are reasons that make sedation less suitable. The decision is made together with the gastroenterologist.

In either case, the bowel is inflated with carbon dioxide (CO2) rather than air. CO2 is absorbed quickly by the body, so bloating and abdominal discomfort after the examination are clearly reduced.

Preparation

Preparation largely determines the value of the examination. A bowel that has not been cleaned properly means lesions that will not be seen, and often a repeat examination sooner than planned.

Preparation includes a low-residue diet in the days before, taking a special bowel-cleansing solution according to the instructions, and drinking enough clear fluids. The exact instructions are personalized, depending on the time of your appointment and your medical history. It is important to tell your doctor about your medication, especially anticoagulants, antiplatelet drugs, insulin or iron supplements.

The patient fasts for 6 to 8 hours and follows a specific bowel-cleansing regimen.

Can colonoscopy be done without a laxative? No. There is no reliable colonoscopy without cleansing the bowel. What has changed is the method: modern low-volume preparations, taken as a split dose with part of it on the morning of the examination, are much easier to tolerate than the old four-liter regimens and also clean better.

How it is performed and how long it takes

The patient lies on the left side, with the head on a pillow. The endoscope is advanced to the cecum and the terminal ileum, and the careful inspection takes place mainly while it is withdrawn.

The examination itself usually takes 15 to 30 minutes. When polyp removal or another therapeutic procedure is needed, it takes longer accordingly. With the preparation on site, the examination itself and recovery, the patient should allow two to three hours in total at the practice or clinic.

Technology and diagnostic accuracy

With the help of the latest generation of endoscopes and an artificial intelligence (AI) system, your doctor can accurately identify lesions of the colon, even at early stages, and remove them at the same time.

In this way, your gastroenterologist can use colonoscopy to remove, for example, large and small polyps, which are then examined under the microscope to determine whether they are precancerous or not.

Some polyps, particularly flat and serrated ones, are subtle and can easily be missed in a conventional examination. High-definition techniques, magnification and virtual chromoendoscopy highlight these lesions and allow them to be characterized before removal, guiding the right treatment.

Prevention of colorectal cancer

It is worth noting that colonoscopy is a cornerstone of colorectal cancer prevention, and current guidelines set the starting age at 45 for the general population, regardless of gender.

Most colorectal cancers develop from polyps, through a slow process that usually takes several years. This creates a valuable window of time: colonoscopy finds and removes polyps before they have a chance to progress. Because the early stages usually cause no symptoms, screening should not depend on symptoms appearing.

What can be done during the same examination

• Biopsies to confirm the diagnosis
• Polypectomy, meaning the removal of polyps (with a special snare passed through the endoscope), which are always sent for histological examination
• Endoscopic mucosal resection (EMR) for larger or sessile lesions that cannot be treated with simple polypectomy
• Endoscopic submucosal dissection (ESD) for extensive or flat lesions and early neoplasia, removed in one piece
• Treatment of bleeding and dilation of strictures
• Placement of stents in selected cases

This is also why colonoscopy is superior to every other screening method: it finds and treats in the same procedure.

In the hands of a specialized interventional endoscopist, colonoscopy treats lesions that in the past required surgery. Endoscopic submucosal dissection (ESD) removes even extensive lesions or early neoplastic lesions in one piece, keeping the bowel intact and avoiding the removal of a section of the bowel.

Polyps found during the examination are removed in the same session. A practical example is the removal of multiple pedunculated polyps, where each specimen was sent separately so histology could be matched to its site.

Complications and safety

Colonoscopy is a safe examination. Serious complications are rare, fewer than 3.5 per 1,000 examinations, and mainly involve bleeding after polypectomy and, much more rarely, perforation.

The risk is slightly higher with therapeutic procedures than with a simple diagnostic examination, but it remains low and clearly smaller than the benefit of prevention.

After the examination

After an examination with sedation, the patient stays for recovery and does not drive for the rest of the day. Someone needs to accompany them home.

Eating resumes soon, with a light meal and enough fluids. Mild bloating or cramps are expected and settle quickly, especially with the use of CO2. If a polyp was removed, a small amount of blood in the first bowel movement is not a cause for concern. If a polypectomy was performed, specific instructions are given for diet and activity during the first days.

Contact your doctor immediately in case of persistent or heavy bleeding, severe abdominal pain, fever, persistent vomiting or significant abdominal swelling.

How often is it repeated

After a normal screening examination in a person at average risk, the next colonoscopy is usually scheduled at 10 years.

When polyps have been removed, the interval depends on the histology, their number and their size, according to the guidelines of the European Society of Gastrointestinal Endoscopy. One or two small tubular adenomas with low-grade dysplasia do not require specific surveillance, while a repeat examination at 3 years is recommended for an adenoma of 10 mm or more, high-grade dysplasia, or five or more adenomas.

People with a family history, a hereditary syndrome or inflammatory bowel disease are checked earlier and more often.

Note: This article is intended for informational purposes only and does not replace the detailed explanation and personalized guidance provided by your gastroenterologist regarding the colonoscopy procedure.

Frequently asked questions about colonoscopy and colorectal cancer prevention

How often should I have a colonoscopy to prevent colorectal cancer?

Screening colonoscopy starts at the age of 45 for people at average risk and, if the result is normal, is repeated every 10 years. The interval is shorter (for example 3 to 5 years) when polyps are found and removed, or screening starts earlier when there is a family history of cancer or polyps, inflammatory bowel disease, or symptoms such as bleeding. Dr. Thomas Thomaidis, Interventional Gastroenterologist, personalizes the surveillance plan based on the findings and the medical history.

Which gastroenterologist treats colorectal cancer and performs colonoscopy in Athens?

For colonoscopy and the management of colorectal cancer, you should see a gastroenterologist specialized in the endoscopic diagnosis and removal of precancerous lesions. Dr. Thomas Thomaidis performs diagnostic and therapeutic colonoscopy in Athens, with polypectomy and advanced resection techniques (EMR, ESD) for polyps and early neoplasia of the colon.

Is colonoscopy done with sedation?

As a rule yes, with intravenous sedation and continuous monitoring, so the examination is painless. Beyond comfort, sedation allows slower and more careful inspection and therefore better detection of lesions. It can be performed without sedation when the patient prefers it or needs to drive afterwards. The choice is made together with the gastroenterologist.

How long does a colonoscopy take?

The examination itself usually takes 15 to 30 minutes. If polyp removal or another therapeutic procedure is needed, it takes longer accordingly. Together with the preparation on site and recovery after sedation, the patient should allow two to three hours in total.

Can colonoscopy be done without a laxative?

No. There is no reliable colonoscopy without cleansing the bowel, because residue hides lesions and leads to a repeat examination. What has changed is the method: modern low-volume preparations, taken as a split dose with part of it on the morning of the examination, are much easier to tolerate than the old four-liter regimens and clean better.

Why is the preparation split into two doses?

Because it cleans demonstrably better. Guidelines recommend split dosing for elective colonoscopy, with the second part taken closer to the time of the examination. The bowel is then clean at the moment it matters, and the chance of needing to repeat the procedure falls.

Can I drive after the examination?

No, if it was done with sedation. After sedation the patient stays for recovery and does not drive for the rest of the day, so someone needs to accompany them home. If the examination is done without sedation, this restriction does not apply.

Does colonoscopy hurt?

No. The examination is usually performed under sedation, with continuous monitoring of vital signs, so it is painless and the patient usually has no memory of the procedure. If the patient prefers, it can also be performed without sedation. Any bloating afterwards is mild and temporary, because carbon dioxide is used.

How many hours do I need to fast before colonoscopy?

You need to fast for 6 to 8 hours before the examination. You also need to prepare your bowel properly with the special cleansing solution, following the instructions you receive. The exact timing depends on the time of your appointment, so always follow the specific protocol you were given.

What can I eat after colonoscopy?

Eating is usually allowed shortly after the examination, once the effect of sedation has worn off. Start with light, easily digestible meals and plenty of fluids, and avoid very fatty or spicy food and alcohol on the first day. If a polyp was removed, your doctor will give you specific dietary instructions for the first days.

Is colonoscopy dangerous?

Colonoscopy is an established and safe examination. Complications are rare, occurring in fewer than 3.5 per 1,000 examinations, and are mainly related to therapeutic procedures, such as the removal of large polyps. The risk of not having the examination, when it is indicated, is clearly greater.

What is normal to feel after colonoscopy?

Temporary bloating, gas and mild abdominal cramps are normal, as is a small amount of blood in the first bowel movement if a biopsy or polypectomy was performed. These symptoms settle within a few hours to a day. Severe or persistent pain, significant bleeding, fever or vomiting are not normal and require immediate contact with your doctor.

Do I need someone to accompany me for colonoscopy?

Yes, if the examination is performed under sedation. Because sedation is given, you must not drive or operate machinery on the same day. Someone needs to accompany you when you leave the practice.

Can polyps be removed during the examination?

Yes, and this is the great advantage of colonoscopy. Most polyps, small and large, are removed in the same session. Larger or flat lesions are removed with specialized techniques, such as endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD). The tissue is always examined under the microscope to determine whether the polyp is precancerous.

Can colonoscopy and gastroscopy be done together?

Yes, the two examinations can be performed in the same session and under the same sedation, when both are indicated. This saves time, reduces the overall burden on the patient and requires only one sedation.

Sources

• European Society of Gastrointestinal Endoscopy, Post-polypectomy colonoscopy surveillance: ESGE Guideline Update 2020. https://doi.org/10.1055/a-1185-3109
• American Cancer Society, American Cancer Society Guideline for Colorectal Cancer Screening. https://www.cancer.org/cancer/types/colon-rectal-cancer/detection-diagnosis-staging/acs-recommendations.html
• Hassan C et al., Bowel preparation for colonoscopy: ESGE Guideline Update 2019. https://doi.org/10.1055/a-0959-0505