Overview of Colonoscopy
A colonoscopy is a procedure that allows your doctor to look at your large intestine, which includes your colon, rectum, and anus. It can also be used to examine the last part of your small intestine, known as the terminal ileum. The doctor uses a flexible, tube-like instrument called a colonoscope to do this.
The colonoscope has a high definition camera on the end, and it can also have channels that allow the doctor to use equipment and fluids. Using fluids helps to clean the lens of the camera and the lining of your intestine, called the mucosa. The camera sends images to a screen, so the doctor can spot anything unusual or abnormal in your intestine. This can include places where the intestine wall is overgrown.
Doctors can also use special instruments with the colonoscope to take small tissue samples, called biopsies, or to remove lesions from the lining of the intestine. Because it can do so many things, the colonoscopy has become a very important tool in preventing and detecting colorectal cancer early. In fact, in the past few decades, it has greatly improved our ability to keep people from getting colorectal cancer, or to catch it at an early stage when it can be more successfully treated.
Anatomy and Physiology of Colonoscopy
The digestive system is divided into three parts: the upper part, middle part, and lower part. The upper part includes the mouth up to the second part of the small intestine. The middle part consists of the remaining portions of the small intestine up to the majority of the large intestine. The lower part includes the last third of the large intestine down to the anus.
Understanding these divisions is significant when it comes to dealing with any issues associated with the digestive system and making any surgical plans, especially related to the large intestine. The digestive system, after the stomach, is broken up into the small intestine and the large intestine. Going from close to the body, outwards, the small intestine is further divided into the duodenum, jejunum, and ileum. The ileum ends at a valve that opens up into the first part of the large intestine, termed as the cecum. The cecum is a small bag-like structure that proceeds onward as the ascending colon, then the transverse, descending, and sigmoid colon. The colon empties into the rectum and finally the anal canal.
On average, the distance from the anus to the cecum ranges from 120 cm to 160 cm. Two main blood vessels, the superior mesenteric artery (SMA), and the inferior mesenteric artery (IMA), supply blood to the colon. It’s crucial to remember these details when undergoing procedures like a colonoscopy and identifying the location within the colon.
Like the small intestine, the colon consists of various layers. One key difference between the small and large intestines involves the arrangement of muscle layers. The muscle layer in the colon is grouped into three bandlike structures. In addition, the colon has small bulges or pouches, which can be important to remember during a colonoscopy as these pouches can hide small growths.
The length and width of the colon are significant when performing colonoscopies. The length of different sections are as follows:
- Anal canal: 4 cm
- Rectum: 15 cm
- Sigmoid colon: 50 cm
- Descending colon: 10 cm
- Transverse colon: 50 cm
- Ascending colon: 10 cm
- Cecum: 5 cm
Given these estimates, it’s the various landmarks and differences in the width, color, blood vessels, and anatomy of the colon that help identify location, as the colonoscope can loop on itself and not provide an accurate length measurement.
Why do People Need Colonoscopy
A colonoscopy is a medical procedure that allows doctors to examine the inside of your large intestine. It is performed for a variety of reasons and can be divided into two main categories: diagnostic and therapeutic.
Diagnostic procedures may be carried out as either screening or elective tests. Screening colonoscopies are intended to check for colorectal (colon or rectum) cancers depending on a patient’s risk levels. These risks can be average or high.
If your risk is average, the first screening usually starts at the age of 50 and is done every 10 years, given that no disease or condition was discovered that might increase your risk. These routine checks are known as surveillance colonoscopies. A repeat test might be conducted earlier depending on the findings from the first procedure (index procedure).
For patients who have a high risk of developing colorectal cancer, the screening is done before age 50 and repeated every 1, 2, or 5 years, based on your primary risk factors and results from previous procedures. Factors that may put you at high risk include a history of inflammatory bowel disease, a family history of colorectal cancer diagnosed before age 60, a genetic tendency to develop polyps (like Peutz Jegher syndrome and Familial Adenomatous Polyposis), and non-polyp syndromes (like LYNCH I and II). If you have close relatives diagnosed with colon cancer, it is advised that you get a colonoscopy by age 40, or 10 years before they were diagnosed, whichever comes first. An elective colonoscopy is performed when symptoms such as unexplained changes in bowel habits, blood in stool, unexplained weight loss among older adults, persistent stomach pain, suspected inflammation or infection in the colon, or radiographic abnormalities.
Therapeutic colonoscopy is meant for treatment purposes, such as the removal of lesions, treatment of bleeding lesions, widening of a narrowed area, removal of foreign objects, unwinding of a twisted colon or in managing terminal illnesses.
The United States Preventative Services Task Force (USPSTF) recommends that average-risk individuals between ages 50-75 years should get a colonoscopy every 10 years. Other tests, such as fecal occult blood tests (FOBT), yearly with flexible sigmoidoscopy every 5 years, and fecal immunochemical testing, are often for those with an average risk of colorectal cancer and are not typically recommended for high-risk individuals.
Colonoscopy is not only great for diagnosing colorectal cancer, but it can also help diagnose, treat, and develop treatment plans for inflammatory, mechanical, and anatomical diseases like Crohn’s disease, ulcerative colitis, and sigmoid volvulus.
When a Person Should Avoid Colonoscopy
A colonoscopy is a test that helps doctors identify issues in the colon, whether they’re lasting (chronic) or temporary (acute). However, there are certain circumstances where a colonoscopy might not be the right choice of treatment. Understandably, a patient must want to go through with the test. Preparing for a colonoscopy, which includes drinking a special liquid, may be uncomfortable and tough if a patient doesn’t want to proceed. In addition, active inflammation, or swelling and redness from various conditions like toxic megacolon, serious colitis, ulcerative colitis, Crohn’s disease flares, diverticulitis, and more, should be held in mind when thinking about a colonoscopy.
Performing a colonoscopy can increase the size of the colon and apply extra pressure inside it. This can be dangerous for inflamed and fragile tissue, as it makes the risk of tearing a hole (perforation) higher. So, it’s often a good idea to delay the colonoscopy until the inflammation has reduced. Some absolute reasons not to have a colonoscopy are if a patient refuses, they’ve recently had a heart attack, they’re medically unstable, they have peritonitis (a serious inflammation of the abdominal lining), they’ve recently had surgery involving the colon, or they’ve suffered and been treated for bowel injury. Generally, it’s recommended that patients wait at least 6 weeks after an acute event before having a colonoscopy.
Equipment used for Colonoscopy
A colonoscopy involves using specific tools and a team of trained professionals. The room where the procedure occurs is set up with high-quality screens, a device to gently inflate the intestine for better examination, a suction tool, several grasping tools, and means to wash the intestine.
A colonoscope, which is the main tool used for the procedure, is a long flexible, sturdy tube. It can be easily cleaned and operated by one person. There are different sizes for adults and children. The tube is about 160-180 cm long and roughly 1.0-1.2 cm wide. This can vary depending on the maker and the size of the scope. The end of the colonoscope is equipped with two or three lenses to improve the visibility of images, two LED lights for light, and two tiny holes used to pass irrigation and other tools.
The colonoscope’s handle is designed to be held with the left hand, while the right hand guides the scope near the bottom area. The rigidity or flexibility of the scope can be adjusted through a dial on the handle. This allows the doctor to navigate through difficult corners but needs to be done carefully as too much rigidity can cause discomfort to the patient and increase the risk of perforation. Additional controls allow for adjusting image quality and various video options, like recording or zooming into areas of interest. There are two wheels attached for manipulation: the larger wheel helps with moving the scope upwards and downwards, and the smaller wheel helps with left and right movements. This configuration offers flexibility and control leading to better visualization of the colon. Without movement, the viewing angle of the scope is approximately 140 to 170 degrees, depending on the model. The scope offers almost a 360-degree view when combined with the movement of the end of the scope.
Before beginning the procedure, it is essential to ensure that the lock on the scope’s movement is released, and that the scope can be freely moved before inserting into the bottom area. If not done, this can cause discomfort to the patient, possibly damage the sensitive tissues in the area, complicate the procedure, and increase the risk of unintended perforation.
The small holes mentioned earlier are important as they let equipment pass through and irrigate the colon. Long wires and tools, including graspers, needles, snares, and clip appliers, can be inserted through these holes. These tools allow for a range of treatments like stopping bleeding, removing potential concerning growths, marking a mass for future surgery plans, or burning concerning and bleeding tissue.
Who is needed to perform Colonoscopy?
For your safety during a colonoscopy (a test to check the insides of your colon), it’s critical that the specially-trained doctor performing the procedure (colonoscopist) has help in the room. This support team, at the very least, includes a nurse to give medications and a technician who helps with getting the equipment ready, making sure you’re positioned correctly, and solving any issues that might come up. Extra helpers in the room can assist with moving you if needed and applying pressure to your belly as necessary. It’s been found that having an experienced assistant can boost how satisfied patients are with their procedure and improve the success of the colonoscopy.
A colonoscopy can be done without the use of an anesthesiologist (a doctor specialising in giving medication to make you sleep or feel no pain) or nurse anesthetist. However, this means the colonoscopist needs to know not only how to perform the examination but also safely give the sedation medication while watching your comfort and relaxation levels. This can split their attention between the inspection and your comfort.
So, to ensure you are as comfortable as possible, it can be helpful to have an anesthetist or nurse anesthetist present. This is especially the case if you are overweight, or have a colon that twists more than usual, or if you have things like an unusual colon shape, specific diseases of the colon or small sacs that are called diverticulosis. They can help ensure deep relaxation, improving your overall comfort and satisfaction during the procedure.
Preparing for Colonoscopy
Many patients find preparing for a colonoscopy to be challenging and uncomfortable. It’s a primary reason some people don’t get this important test. But preparing properly is crucial because it allows the doctor to spot any abnormal tissue or growths in the colon. Insufficient preparation can lead to risks like tearing the colon or missing abnormalities, so it’s essential to follow the preparation steps correctly.
The goal of colonoscopy preparation is to have a clean colon, meaning it’s free of waste material that normally accumulates there. This gives the doctor a clear view of the colon lining during the procedure. The challenge lies in the preparation process which may involve some discomfort. There are several options for clearing out the colon, including various medications and laxatives such as polyethylene glycol, magnesium citrate, magnesium hydroxide, bisacodyl, and sodium picosulfate. Everyone is different, so what works best can vary from person to person.
Although the aim is a clean colon, it’s important to understand that it won’t be completely free of stool. Despite following the preparation steps, people may still pass stool which may have a bit of color. However, as long as the stool is liquid, the doctor can easily wash it away during the colonoscopy. Discomfort during preparation is unavoidable but it can be mitigated by having a clear liquid diet the day before the colonoscopy. Besides, people finding complete clearance in 24 hours difficult, it’s feasible to take a soft nourishment for up to three days prior.
While using an enema before a colonoscopy might help to some extent, it’s not efficient for a thorough cleanse as it can’t effectively reach all parts of the colon. Therefore, it’s not commonly recommended.
There’s ongoing debate about giving antibiotics before a colonoscopy. While there’s no strict rule about this, antibiotics might be considered for high-risk patients who have conditions like immune system disorders, diabetes, or are on dialysis, as they might be more susceptible to infection after a colonoscopy or polyp removal.
It’s crucial for doctors to thoroughly explain the importance of good preparation, procedure, and steps to the patients. Experience shows that taking time to talk about the process can lead to better preparation outcomes and increase the chances of a successful colonoscopy.
How is Colonoscopy performed
Performing a colonoscopy is a complex medical procedure that takes a lot of time, patience, and practice to master. Despite seeming straightforward when observed, the reality involves intricate navigation through a tube (the colon) that isn’t stable but can move and change shape. There are also considerations for each patient’s particular body condition such as weight, past surgeries, and how well the bowel has been prepared for the procedure. A learner clinician needs many practice hours using a simulator and observing an experienced surgeon or a gastrointestinal specialist to get it right.
It’s important for the clinician to know how to use the colonoscope (a special instrument used in a colonoscopy) well and to test it before they start the colonoscopy. The colonoscope has several moving parts that the clinician has to control, which adds to the complexity of the procedure.
The patient lies on their left side. The clinician or a nurse places pillows at the patient’s back, head, and knees to avoid injuries and to maintain the position. The bent knees relax the key muscles and allow a smoother entry past the sacral bone prominence. If the patient isn’t positioned properly, navigating past the rectum becomes more challenging.
The doctor stands behind the patient and first inserts a finger to check for any abnormal feelings such as lumps. The rectal tone, or the tension in the anus, is also felt, although this could be affected by how sedated the patient is.
Following this initial check, the scope is inserted. The doctor uses the controls to navigate the scope through the rectum, colon and finally into the small intestine (also known as the ileum). There are landmarks along this route that the doctor uses to ascertain their location, as using the scope to measure distances isn’t generally reliable. Knowing these landmarks improves with experience.
The procedure needs to be handled gently and it’s crucial not to force the scope if there’s difficulty in advancement. If there’s any resistance, it may suggest formation of a loop in the sigmoid colon (a part of the colon just before the rectum). A loop formation can make a patient uncomfortable. To remove the loop, the scope is carefully pulled back while being rotated in a clockwise direction – this usually resolves the issue and allows for further advancement of the scope.
In order to ensure that no areas have been missed and to confirm that the cecum (the end of the colon) was indeed reached, the doctor should aim to push the scope through the ileocecal valve. This also helps to check the condition of the small intestine and aids in diagnosing conditions like inflammatory bowel disease.
While moving the scope towards the cecum, the inner lining of the colon is examined in detail. It’s important that the doctor carefully observes the images sent by the scope for the best possible results and to ensure patient safety.
Possible Complications of Colonoscopy
Like all surgeries, colonoscopies can pose some risks that should be explained to patients beforehand. General complications can include reactions to anesthesia such as stroke, heart attack, difficulty breathing, and even death. Specific to colonoscopies, patients should be aware that there’s a chance of rectal tears, bleeding, discomfort, bloatedness and infection.
One serious but very rare risk is intestinal perforation, which is a fancy way of saying a hole or tear in the intestines. This happens in about 1 out of every 1000 colonoscopies. This risk is quite low, making colonoscopies a relatively safe procedure and a good method to screen for colon cancer. The perforation can happen anywhere in the colon and the last part of the small intestine, called the ileum. But it’s most commonly found in the sigmoid colon, which is the first bend of the large intestine.
Perforation can happen in a couple of ways: from too much force against the wall of the colon, from over filling the colon with air during the procedure, or from the tools used to remove polyps which are small growths that can become cancerous. In particular, every bend in the colon can get injured as the scope pushes against it to move forward. The first bend, the sigmoid colon, has the highest chance of getting injured.
Another rare but important complication to know about is called post polypectomy electrocoagulation syndrome (PPES). This happens when a polyp is removed using a process called electrocautery, which burns off remaining cells. While the risk is low, a burning injury to the wall of the colon can happen if the doctor does not lift the tissue away from the wall when applying electrocautery. Several hours after a colonoscopy, a patient with PPES might have severe abdominal pain. Blood tests might show an increase in white blood cells, which indicates an infection, and a CT scan might show a swollen bowel and inflamed tissues, but no signs of air inside the abdomen. It’s typically treated with rest, supportive care, antibiotics, and usually heals without the need for surgery. To reduce the chances of PPES, the doctor should lift the polyp away from the wall during electrocautery and inject saline under the polyp to make an insulating layer.
What Else Should I Know About Colonoscopy?
Experts recommend getting a colonoscopy (a procedure to check the insides of your colon) starting at age 50 and then every 10 years until you turn 75. This is because, on average, it takes about 10 years for a small growth (called a polyp) to turn into cancer.
During the procedure, the doctor will look for any suspicious growths that may need to be removed immediately, or that might need closer follow-up or a consultation with a cancer specialist. If the doctor identifies suspicious polyps, they will remove and send them for lab testing. Some types of polyps, like hyperplastic polyps, typically do not lead to colon cancer. However, adenomas, another type of polyp, can be a sign of possible cancer and should be removed if they are larger than 6 mm or display certain features.
The method used to remove a polyp usually depends on its size and shape. Depending on the size and appearance of the polyp, the doctor may mark the location of the polyp with a tattoo to make it easier to find in future colonoscopies or during surgery.
In the United States, colon cancer is the third leading cause of death from cancer for both men and women. This is mainly attributed to our Western lifestyle, which often includes eating red meat, low-fiber diets, smoking, using alcohol, and consuming highly processed foods. Regular screening via colonoscopy can significantly reduce death rates from colon cancer by finding it early when it is more likely to be treatable. Therefore, it’s essential for doctors to be familiar with these screening guidelines and for patients to follow them, starting from age 50 or even earlier if a close relative has had colon cancer.
