A lower GI endoscopy, also called a colonoscopy, is an endoscopic technique that allows us to directly visualize the lower digestive tract, including the colon or large intestine and the terminal ileum or portion of small intestine that joins the colon using a flexible tube with a camera called endoscope.
The lower GI endoscopy or colonoscopy has become, ahead of the traditional radiology screening barium enema, the most important procedure in the early diagnosis and prevention of colorectal cancer. It consists of the detailed exploration of the entire large bowel (colon) and last segment of the small bowel (terminal ileum) where it connects with the colon. This test uses a flexible endoscope.
As in the gastroscopy, the great advantage of these techniques is the ability to obtain small samples of tissue (biopsies) of the explored areas, and accurately diagnose the disease.
How is it carried out?
The colonoscope is a long and flexible fiberoptic tube with a camera that allows the complete examination of the lower intestine. Today, digitally-enhanced, high-definition endoscopes are used. The whole procedure is followed on a TV monitor that allows the physician to very accurately make reliable diagnosis and record the images.
A high quality diagnostic study depends on the correct cleansing of the colon.
Given that the procedure can be uncomfortable and sometimes painful, a light sedation anesthesia is commonly used.
The specialist introduces the endoscope through the anus to begin the examination. During the procedure, air must be introduced into the bowel to distend it. This will often cause crampy pain. Flatus will often alleviate these symptoms.
What are its uses?
As in the upper endoscopy, the colonoscopy allows us to make or exclude the diagnosis of diseases of the intestinal tract. It also permits certain interventions that have become extremely important, particularly in the prevention, screening and early diagnosis of colo-rectal cancer. These are called polypectomies and consist of the removal of pre-cancerous lesions or polyps. It also allows other interventions such as control of bleeding lesions, biopsies or dilatations of post-surgical narrowing or strictures.
When should it be performed?
There are several indications:
1. Passage of blood through the anus, even if the patient has known hemorrhoids.
2. Suspicion of Inflammatory Bowel Disease (I.B.D.) such as ulcerative colitis and Crohn's Disease. The most common symptoms of these are abdominal pain, diarrhea mixed with blood and fever.
3. New-onset of severe constipation.
3. Persistent and chronic diarrhea.
4. Regular monitoring of patients who have had surgery for colon or rectal cancer. This is done regularly, usually once or twice a year.
5. Patients with abnormal radiology studies that demonstrate such findings as narrowing of the bowel, polyps or tumors and those who need to have biopsies taken.
6. Monitoring patients with a history of polyps. These regular follow-up tests will be carried out in accordance with the size, number and type of polyp obtained in the biopsy. It is generally done every 2-3 years.
7. Studying the family members of patients with colorectal cancer:
8. Patients that are at a higher risk for developing colorectal cancer.
It is compulsory to carry out the examination if there is a history of:
- Familial Colonic Polyposis: Given the extreme risk of cancer in patients with this disease, screening colonoscopies should be performed annually until an optimum time for surgery is decided. It is currently possible, through a blood test, to identify the level of risk of developing a tumor.
- Hereditary non-polyposis familial colorectal cancers: The screening colonoscopies must be initiated 10 years earlier than the age in which the cancer was first found in the family member. It must be repeated every two years.
- Two or more family members with colorectal cancer: The procedure should be carried out every 3-5 years beginning at the age of 40.
9. Patients that are at moderate risk for developing colorectal cancer
It is necessary to carry out the endoscopy if:
- There exists a family member who was diagnosed with colorectal cancer before the age of 50. Screening colonoscopies should take place every 5 years. The first should be done 10 years before the patient reaches the age of the family member at the time of diagnosis.
10. Patients that are at low risk for developing colorectal cancer.
An endoscopy should be performed if:
- There exists a first-degree relative (father, mother) with colorectal cancer that was diagnosed after age 50. The screening colonoscopy should be performed every 5 years starting at around 40-50 years of age.
Polypectomy: This consists of the removal of colonic polyps, which are superficial tumors of the wall of the colon. It is carried out using a special probe that conducts an electrical current, produces heat and allows for the excision of the polyp while controlling any bleeding.
It is necessary to check for clotting disorders before performing this procedure.
Dilatation of a narrowing (stenosis): This is an uncommon indication, and it is used in situations where scarring has occurred after surgery. The colonoscopy allows the introduction of balloons that, once placed in the area of stenosis or narrowing, are inflated with air or water and, in some cases, are able to widen it.
Which factors interfere in the results?
Carrying out the examination without thorough preparation and cleansing of the colon severely hinders the test. If the colon is full of stool, adequate visualization of the bowel wall is impossible.
Which doctor has to carry out the test?
The exploration must be carried out by a specialist in digestive tract with extensive knowledge and advanced training in endoscopy.
Does it require any special preparation on the part of the patient?
The patient should not take solids food at least 6 hours before the procedure and liquids at least 4 hours before the test. Additionally, a careful cleaning of the colon must be done by taking several laxative combinations and a low-residue diet starting the day before the test. All these medications will be prescribed by your physician.
What conditions could impede the study?
The circumstances that contraindicate the procedure are few but include:
- Severe and acute inflammation of the colon (colitis).
- Acute diverticulitis (inflammation of the disease diverticulosis) due to high risk of colonic perforation.
- Known perforation of the colon.
Can there be complications?
A colonoscopy is a very safe procedure but there is a risk of complications. These present in a very low percentage (0.2 - 1%) of patients. Among the complications it is necessary to highlight: perforation of the colon, bleeding from the bowel wall, especially after a polypectomy and infection from the passage of digestive bacteria into the blood. The mortality rate is also extremely low (0.01% - 0.03%).