Colonoscopy: Procedure, Preparation, and Innovations

What is a Colonoscopy?

A colonoscopy is a medical procedure conducted by an examiner, often a gastroenterologist, to assess the interior of the colon, also known as the large intestine or large bowel. Utilizing a four-foot-long, flexible tube with a camera and a light source at its tip (colonoscope), the examiner navigates through the anus, advancing it slowly under visual control to examine the rectum and the colon, typically reaching the cecum—the initial part of the colon. In certain cases, the last few inches of the small intestine (terminal ileum) can also be examined.

Why is a Colonoscopy done?

Colonoscopies are performed for various reasons, primarily as part of screening programs to detect colon cancer. Additionally, they are conducted to investigate issues such as blood in the stool, abdominal pain, diarrhea, changes in bowel habits, or abnormalities observed in colonic X-rays or CT scans. Individuals with a history of polyps or colon cancer, as well as those with a family history of specific non-colonic cancers or colonic problems associated with colon cancer risk, might be advised to undergo periodic colonoscopies.

How often one should undergo a colonoscopy depends on the risk level for cancer and previous findings. Generally, healthy individuals at normal risk should have their first colonoscopy at age 50 and repeat it every 10 years.

What bowel preparation is needed?

For an accurate and complete procedure, the colon must be thoroughly cleaned, and various colonoscopy preparations are available. Patients receive detailed instructions, typically involving drinking a special cleansing solution or adhering to a clear liquid diet along with laxatives or enemas in the days leading up to the examination. Following these instructions precisely is crucial to prevent unsatisfactory results, potential procedure repetition, or resorting to less accurate alternative tests.

Can I take medications before a Colonoscopy?

Most medications can be continued as usual, but it is essential to inform the colonoscopist about all current prescription and over-the-counter medications. Special instructions may be needed for medications like aspirin, blood thinners, arthritis medications, insulin, and iron preparations. Awareness of allergies and major illnesses is crucial, and if antibiotics were previously required before surgical or dental procedures, the colonoscopist should be alerted.

What should I expect during Colonoscopy?

Before the procedure, intravenous fluids are administered, and the patient is monitored continuously for heart rhythm, blood pressure, and oxygen levels. Sedatives are usually given through an intravenous line to induce relaxation and reduce pain. Patients may experience pressure, cramping, or bloating during the procedure, but with the aid of medications, it is generally well-tolerated. The examination involves slow advancement of the colonoscope, taking 15 to 60 minutes. If the entire colon cannot be visualized, the physician may schedule a repeat colonoscopy with a different preparation or opt for alternative tests.

What if abnormalities are detected?

If abnormalities are identified, biopsy forceps can be used to obtain tissue samples for microscopic analysis. Biopsies can help evaluate abnormal areas, identify infections, or pinpoint the source of bleeding. Polyps, often benign growths with the potential to become cancerous, can be removed through the colonoscope. The procedures are typically painless, and a biopsy does not necessarily imply cancer suspicion.

What should I expect after Colonoscopy?

Patients are observed for an hour or two post-colonoscopy until the effects of medications wear off. If sedatives are used, patients are advised against driving and must have someone else transport them home due to the potential impairment of reflexes and judgment. Mild cramping or bloating can be alleviated by passing gas, and patients can resume eating once home. Restrictions on diet or activities, if any, are usually brief and depend on specific procedures performed during the colonoscopy. Findings can be discussed with the patient before departure, but a definitive diagnosis may require microscopic analysis of biopsy specimens, which takes a few days.

What are the possible risks, complications, or alternatives?

Complications from colonoscopy are rare and generally minor when performed by trained and experienced professionals. Possible complications include minor bleeding at biopsy or polyp removal sites, which is typically self-limiting or controllable through the colonoscope. Perforations or tears in the colonic wall are even less common and may not necessitate surgery.

Other potential complications include reactions to sedatives, localized irritation at injection sites, or complications related to existing heart or lung disease. The overall incidence of complications is less than 1%. Patients should be vigilant for early signs of complications, such as severe abdominal pain, significant rectal bleeding, or fever and chills, and contact the colonoscopist promptly if noted.

Colonoscopy is considered the gold standard for detecting, diagnosing, and treating colonic abnormalities. Alternatives are limited, with barium enema being less accurate and often requiring follow-up colonoscopy. Flexible sigmoidoscopy is a more limited examination, focusing on the last one-third of the colon.

What is a Virtual Colonoscopy?

Virtual colonoscopy is an alternative technique using CT scanning to generate virtual images of the colon similar to those observed during direct colonoscopy. The procedure involves cleansing the colon with laxatives and injecting air into the colon before obtaining CT scans. While virtual colonoscopy can be effective, it has limitations, particularly in identifying small polyps or flat cancers. Additionally, it exposes individuals to moderate radiation and may still require a follow-up colonoscopy for polyp removal.

What’s new in Colonoscopy?

Several advancements aim to improve the detection of challenging lesions, such as small polyps or flat lesions, and enhance the ability to determine the need for biopsies or removal during colonoscopy. Innovations include high-resolution imaging, magnification of images, narrow-band imaging, chromoendoscopy, fluorescence endoscopy, and confocal laser endoscopy. Some technologies attempt to provide a retrograde view of the colon in addition to the standard forward view, enhancing lesion identification. While these techniques show promise, their widespread use and efficacy are still being determined. Magnetic resonance imaging (MRI) is another option, offering a radiation-free alternative to CT virtual colonoscopy with similar limitations.


Colonoscopy remains a vital tool for colorectal health, and ongoing advancements aim to enhance its capabilities, providing patients with more accurate and efficient diagnostic and therapeutic options.’


UpToDate. Patient information: Colonoscopy (Beyond the Basics).

Leave a Comment