Side Effects of Screening Colonoscopies

by Konstantin Monastyrsky, Pharmacist & Author of “Gut Sense”


According to ‘The Annals Of Internal Medicine,’ the rate of serious complications from colonoscopy screening is “10 times higher than for any other commonly used cancer-screening test.”  This number doesn’t include deferred complications, such as internal bleeding, severe anemia, heart attack, stroke, pulmonary embolism, pneumonia, kidney failure, intestinal obstruction, and others.

These complications explain why, according to the Telemark Polyp Study I, colonoscopy screening increases relative mortality by 57%. Thus, if you are seriously considering to undergo screening, your odds of being killed or injured by the side effects of colonoscopy may actually exceed your odds of getting colorectal cancer in the first place [1].

Adding insult to injury, all that prep, fear, risk, expense, embarrassment, and stress are for naught anyway — screening colonoscopy offers near zero protection from colon cancer, as I explain in myDeath By Colonoscopy report.

What gives? Well, a conventional colonoscopy isn’t simply a routine doctor’s visit, but an ambulatory surgical procedure performed under general anesthesia. According to the same Annals of Internal Medicine, serious complications occur in 0.5% of all cases [link].

Unreported medical errors and deferred side effects, such as severe anemia caused by blood loss, pulmonary embolism, heart attack, or stroke related to blood clots caused by general anesthesia, pneumonia, persistent post-operative infection, or kidney failure and acute diverticulitis caused by colon prep, may easily add up to another percent or two.

If, for argument sake, the combined number of complications, side effects, and medical errors tally up to just 1%, it means that 140,000 people are injured annually by 14 million estimated screenings alone. This rate of “collateral damage” is just as high as the incidence of colorectal cancer itself, and, perhaps, is just as deadly, especially for seniors — a primary target group for “preventative” colonoscopies.

Even if you take at face value the claim that screening colonoscopies have reduced colorectal cancer mortality by 5% or about 2,500 lives annually, it means 56 people  have been needlessly harmed to save just one life (140,000 / 2,500).

Then, consider the 1 in 5 chance of getting any other cancer following a single virtual colonoscopy. Radiation exposure from just one abdominal CT scan (at 5 to 10 mSv) is two to three thousands times more potent than a single dental x-ray, and 2 to 3 times higher than the  estimated exposure to a “dirty” nuclear bomb estimated at just 3 mSv [link].

As scary as the “dirty bombs” are, an explosion in the center of Fairfax County, VA, a populous suburb of Washington, DC, would affect only 19,500 people [link]. That is 50 to 100 times less people than are  being nuked annually in the radiology centers across the nation while administering unneeded and cancer-causing abdominal CT scans.

Since preventive colonoscopies became an outright fad after Ms. Couric’s televised colonoscopy in March of 2000 [2], close to 30,000 more people annually have been affected by colon cancer.
Without a doubt, unnecessary screening colonoscopies — conventional and virtual alike, and almost all related to the Katie Couric Effect, — contribute to these new cancers by causing the following common side effects:

  • Intestinal flora disruption.Each successive colonoscopy damages natural intestinal microflora, because this procedure requires a thorough lavage — a washing out of the large intestine with large doses of synthetic laxatives, followed by bowel irrigation with polyethylene glycol and hypertonic electrolytes.

Polyethylene glycol is a habit-forming osmotic laxative found in MiraLax, Colyte, and GoLYTELY. Hypertonic electrolyte is a solution of sodium biphosphate and sodium phosphate found in Fleet Enemas. Both substances kill bacteria on contact just as reliably as a salt gargle kills bacteria in your mouth.

The damage of intestinal bacteria — a condition called disbacteriosis (dysbiosis) — is a key factor behind irregularity, constipation, irritable bowel syndrome, diverticular disease, and inflammatory bowel diseases, such as ulcerative colitis and Crohn’s disease, known, in turn, to raise the risk of colon cancer up to 32 times. That’s 3,200%, if you prefer it that way!
All of the above conditions cause fiber dependence to relieve them. Also, disbacteriosis contributes to colon cancer, because these synergistic bacteria protect intestinal mucosa from numerous types of cancer-causing pathogens. (More on this here.)

  • Disruption of stools. If you are already affected by hemorrhoids, chronic constipation, irritable bowel syndrome, or diverticulosis, then bowel prep, intubation, and lavage may flare up and worsen these conditions considerably by disrupting an established defecation pattern — a situation very similar to the outcome of severe diarrhea.
  • Post-interventional complications. Serious complications, such as colon perforation, occur in 5 out of every one thousand colonoscopies [3]. The risks of delayed bleeding, infection, and ulceration are even higher, but they rarely get reported in connection with colonoscopy.
Colonoscopy with biopsy or polypectomy [polyp removal —KM] is associated with increased risk for complications. Perforation may also occur during colonoscopies without biopsies.” Ann Intern Med. 2006 Dec 19;145(12):880-6;
  • Increased risk of deferred strokes, heart attacks, and pulmonary embolisms. You must also consider the risk of blood clotting, which is a common side effect of anesthesia, particularly among patients with diabetes or heart disease. These blood clots may cause a deadly pulmonary embolism, stroke or heart attack weeks after the colonoscopy;
  • Infections. There is an omnipresent risk of an infectious disease, such as pneumonia or pyelonephritis, associated with any medical procedure performed under anesthesia.
  • Missed tumors create a false sense of security. According to multiple studies, even thorough doctors miss from 15 to 27 percent of polyps, including 6 percent of large tumors. According to the research published in The New England Journal of Medicine [link], some doctors rush through colon exam so fast, that they may miss even cancer in full bloom. One such doctor can process 20 to 30 patients a day [] with assembly line efficiency. Some are known to perform as many as 60 colonoscopies in a single day because the average payment ranges from $1,500 to $2,000 per patient regardless of time spent.
  • Triple jeopardy. (1) According to the American College of Gastroenterology[6], virtual colonoscopies miss 27 percent of colorectal lesions, including pre-cancerous colon polyps and actual cancerous tumors. (2) To add insult to injury, even if the radiologist finds a polyp or two, you’ll need to undergo a regular colonoscopy anyway to remove them. The incidents of false positive readings are also common, according to the same FDA document. (3) As I already pointed out earlier to the FDA’s analysis, the additional cancer risk associated with just one CT scan to detect colon cancer is 1 chance out of 5, or 20%  [5]. These odd are 4 to 8 times higher than your “natural” risk of colorectal cancer at 2.5% to 5%.

Common side effects of colonoscopy
The side effects of colonoscopy are similar to problems associated with any surgical procedure and are caused by the confluence of like factors: bowel prep, mechanical and surgical traumas by instruments, anesthesia, hypothermia, stress, opportunistic infections, fluctuations of blood sugar, excessive fluid consumption, sudden diet modification, and so on. Each stage introduces its own set of complications:

  • Before the procedure: Osmotic laxatives and lavages cause inevitable dehydration and an imbalance of electrolytes — a particularly serious issue for people with heart and kidney disease.
  • During the procedure: mechanical impact of intubation on the anus, rectum, and mucous membrane, possible abrasions by the endoscope; tissue injuries from polypectomy (polyp removal) and biopsies; hypothermia (low body temperature) related to anesthesia — the common cause of bacterial infections (similar to catching colds, flu, pneumonia, or pyelonephritis (kidney infection) after an extended exposure to cold).
  • Immediately after: A slowing or shutdown of gastric and intestinal peristalsis from anesthesia may cause severe dyspepsia, food poisoning, intoxication from the rotting of undigested protein, gastritis, duodenitis, pancreatitis, cholecystitis, enteritis, and obstruction anywhere along the entire digestive tract. These conditions are often exacerbated by a quick resumption of the usual diet (i.e. solid food).

A few days following colonoscopy, side effects are commonly exacerbated by following routine advice to increase fiber intake. These complications may differ in nature depending on the degree of disbacteriosis.

Patients with severe disbacteriosis may not experience much if any bacterial fermentation of fiber and associated gases and bloating but may be affected by large stools, straining, constipation, hemorrhoids and obstruction. Those who retained some bacteria following the test may experience fermentation-related bloating, cramps and flatulence.

Post-traumatic stress syndrome (PTSS) is commonly associated with any invasive procedure in general and cancer screening in particular. It is especially bothersome among persons in a high-risk group or susceptible to anxieties and depression. PTSS commonly interferes with digestion because an elevated level of stress hormones and muscular tensions inhibit the secretion of digestive fluids and peristalsis.

Here is a specific list of the most likely side effects you may experience after the colonoscopy in (more or less) chronological order:

Severe dehydration
Osmotic laxatives used for bowel prep cause a significant loss of body fluids. A rehydration isn’t simply a matter of drinking more water — it takes time because the body can only absorb a limited amount of water at any given time. Resuming solid food soon after a colonoscopy may intensify dehydration because solid food, particularly protein, requires several liters of saliva and digestive juices.
YOUR ACTION: Hydrate yourself properly before the procedure. The best form of hydration is freshly-squeezed cucumber juice (with skin on) — a sugar-free source of potassium, about 600 mg per cup; mineral water with a high-mineral content; and several salty snacks because sodium chloride is essential to retain water. Start rehydration several days in advance — it isn’t a matter of just drinking several glasses of water before the procedure.

Intoxication and food poisoning
These two related conditions may result from a rapid resumption of solid food particularly containing protein. The preceding liquid diet and residual effect of anesthesia cause the reduction of gastric digestion (i.e. an inadequate level of hydrochloric acid and proteolytic enzymes). Inadequate acidity may fail to properly sterilize incoming food from bacterial and viral pathogens.

The unchecked presence of pathogens may cause a condition commonly referred to as “stomach flu”: — nausea, vomiting, diarrhea, abdominal cramps and other symptoms typical to infectious disorders of the GI tract. The enzymatic deficiency (combined with low acidity) results in putrefaction (rotting) of undigested proteins inside the stomach and intestines. This process produces cadaverine — a foul-smelling substance produced by protein hydrolysis. A gradual absorption of this substance into the blood may cause symptoms similar to food poisoning.

YOUR ACTION: Resume solid food gradually. Refrain from proteins for at least 3 days after the colonoscopy. Chew well and thoroughly to improve digestion. Do not drink fluids after meals, only 30 to 60 minutes before, so fluids have a chance to get down into the small intestine where they assimilate. Do not mix proteins with carbohydrates and fiber to ease the digestive load. Do not overeat. Do not consume more than one protein-containing meal a day. Use proteolytic enzyme supplements to assist in the digestion of protein. Make sure to consume the recommended 4-6 grams of salt daily to facilitate the proper synthesis of hydrochloric acid (salt is a source of chloride (Cl). Do not take acid reducers because they inhibit the digestion of protein and release of proteolytic enzymes. Do not take dietary fiber because it extends digestion and causes obstructions. Use the Colorectal Support Kit instead to normalize defecation without fiber.

Esophageal, gastric, duodenal, and intestinal obstructions
Foods are propelled through the digestive tract via peristalsis — a coordinated action of smooth muscles that make up the circumference of the esophagus, stomach, and intestines. Anesthetics, even mild ones, switch off peristalsis for a good chunk of the time particularly in combination with common drugs for hypertension, heart disease, anxiety, depression, convulsions, pain relief (opiates), and some others.

If you follow your doctor’s advice, and take fiber-rich food or fiber laxatives soon after the colonoscopy, there is a good chance of clogging up the GI tract with this rapidly expanding fiber. The obstruction may cause a broad number of digestive complications and problems and may require emergency surgery. Nausea and vomiting, particularly with bile, is one of the most prominent symptoms of intestinal obstruction.

YOUR ACTION: Avoid fiber supplements and food rich in fiber. Use Colorectal Recovery Kit instead to normalize defecation without fiber.

Colorectal bleeding
This is a serious concern for people taking blood thinners and/or aspirin. The removal of polyps leaves a wound. It may not properly heal for several reasons: vitamin K deficiency related to prior disbacteriosis and low-fat diets, ongoing therapy with blood thinners and/or aspirin, collagen synthesis defects related to a low level of vitamin C and protein deficiency, an infection from pathogenic bacteria, elevated acidity and/or a high-level of alcohols from fermenting fiber, mechanical impaction from expanded fiber, irritation and inflammation caused by laxatives and, finally, colon stretching from gases and/or straining.

YOUR ACTION: Use Colorectal Recovery Kit before and after colonoscopy to facilitate healing, reduce inflammation, restore intestinal flora and enable normal and timely defecation.

An outcome of disbacteriosis and inflammatory conditions inside the colon, both caused by bowel prep and dietary fiber, particularly soluble fiber found in psyllium laxatives (Metamucil). The lack of intestinal bacteria compromises stool formation. Inflammation blocks fluids from absorption and causes an additional oozing of mucus into the lumen (colon cavity). Both conditions result in diarrhea (liquid stools). Excessive use of soluble fiber in food and laxatives blocks the absorption of digestive fluids and further exacerbates diarrhea.

YOUR ACTION: Use Colorectal Recovery Kit immediately following a colonoscopy to restore intestinal flora and eliminate inflammatory bowel disease. Avoid fiber laxatives and food that is rich in fiber. Exclude bananas, prunes and prune and beet juice. These common remedies for constipation contain sorbitol — a sugar alcohol and potent laxative. Sorbitol is a primary substance behind diabetic nerve and blood vessel damage, the factors behind diabetic neuropathies (nerve damage), retinopathy (blindness), erectile dysfunction, kidney failure, heart disease and amputation of lower limbs. (87,000 a year in the United States alone).

Small, hard stools
This condition is common after colonoscopy, particularly among patients who refuse to take fiber and results from disbacteriosis caused by bowel prep. Live and dead intestinal bacteria retain fluid (moisture) in formed feces. Even a 10% to 15% reduction of fluids (75% to 80% is a norm) in stools causes small, hard, lumpy stools.

This is, incidentally, why insoluble fiber is recommended in the first place: cellulose (an indigestible component of fiber) expands with water and bulks up stools. Alas, cellulose isn’t as efficient at holding water as bacteria because it dries out faster and results in anal abrasions. It gets fermented by the remaining bacteria which results in gases and bloating and requires a good dosing of insoluble fiber to keep the moisture locked inside – this results in diarrhea and more fermentation. On top of this, enlarged (bulked up) stools require straining which causes hemorrhoids, abrasions, fissures, prolapses and nerve damage.

YOUR ACTION: Use Colorectal Recovery Kit instead of fiber immediately following colonoscopy to restore normal stool morphology.

Flatulence, bloating, abdominal cramps.
Intestinal bacteria reside in the mucous membrane and inside the appendix. Many bacteria will die after the bowel prep but some may survive, particularly inside the appendix. When, following a doctor’s advice, fiber is added to the diet, these bacteria spring into action and ferment the fiber — a process no different from beer, dough, or wine making. Gases, produced by fermentation, cause flatulence, bloating and cramps.

Women are particularly sensitive to gas-related bloating because the genitourinary organs reside in the same tightly packed abdominal cavity. The uterus and fallopian tubes are particularly sensitive to pressure before and during periods, hence the typical after-effects of premenstrual syndrome (PMS). The alcohols and acidity related to fermentation may cause mucosal inflammation which further inhibits the absorption of gases, and increases bloating, flatulence and pain.

YOUR ACTION: Do not use fiber and fiber laxatives following colonoscopy. Your doctor’s advice to use fiber is wrong because it is based on outdated and falsified information. Use Colorectal Recovery Kitinstead to restore proper stool morphology without fiber and laxatives.

Internal and external hemorrhoids are caused by large stools (from fiber) and the ensuing straining to expel them, or by intense, often involuntary contractions of anal and pelvic muscles in response to diarrhea, caused by disbacteriosis and soluble fiber.

YOUR ACTION: Use Colorectal Recovery Kit instead of fiber immediately following colonoscopy to restore normal stool morphology (i.e. reduce stool size, maintain moisture, eliminate straining.)

Anal fissures
Same reasons as above. The mechanical pressure of large stools on the narrow, anal canal passage-way causes skin tears. Daily effort to move the bowels and straining doesn’t allow the wounds to heal and the tear becomes larger and larger. Medication, infection (by passing stools) and malnutrition further interfere with healing.

YOUR ACTION: Use Colorectal Recovery Kit to facilitate the healing process and maintain soft, semi-liquid stools until complete healing. Thereafter, to maintain proper stool morphology so you don’t have to strain.

Chronic constipation
All of the above reasons. As fiber makes stools larger and larger, the anal- canal gets smaller and smaller from internal hemorrhoids. The ensuing pain and discomfort from large stools passing through the narrow anal-canal lead to incomplete emptying and stools remaining in the large intestine get larger, denser, and drier. A vicious cycle of dependence on laxatives to move the bowels ensues.
YOUR ACTION: Use Colorectal Recovery Kit to restore and maintain proper stool morphology.

Irritable bowel syndrome
An alternating pattern of constipation and diarrhea along with abdominal pain, cramps, and discomfort caused by bloating and flatulence. It doesn’t take a genius to recognize the cause — they are all enumerated above. If you already have a history of irritable bowel syndrome, a colonoscopy and more fiber will only make this situation worse.

YOUR ACTION: Use Colorectal Recovery Kit and follow my recommendation in Fiber Menace. I’ve been IBS-free since I started doing   the same and so are thousands of my readers. This is the safest and least expensive approach to become and stay IBS-free for the rest of your life.
You aren’t likely to hear about it from the mainstream medical sector any time soon because it will deprive countless endoscopists, gastroenterologists, hospitals, clinical labs, radiology centers, and drug companies from one of their top money makers, according to the National Institutes of Health:
“As many as 20 percent of the adult population, or one in five Americans, have symptoms of IBS, making it one of the most common disorders diagnosed by doctors. It occurs more often in women than in men and it begins before the age of 35 in about 50 percent of people.” [7]

Colon obstruction
Excessive accumulation of unfermented fiber inside the colon on one hand and an incomplete emptying of stools on the other, may eventually cause fecal impaction and colon obstruction. It’s usually manifested by paradoxical diarrhea — a condition when fluids incoming from the small intestine flow around impacted stool and create a diarrhea-like condition. If you aren’t overweight (fat interferes with manual examination), an obstruction is easily determined during physical examination. Otherwise, an x-ray with contrast solution may be required. Insist on an abdominal x-ray instead of a CT-scan to reduce your radiation exposure.

YOUR ACTION: DO NOT use Colorectal Recovery Kit or any other medication/laxatives, particularly fiber, to manage this condition. This is a real medical emergency which requires an immediate visit to an emergency room for examination and if necessary, manual disimpaction (a procedure performed by a surgeon or a specially-trained nurse). After proper diagnosis and disimpaction, use Colorectal Recovery Kit to prevent any repeat occurrence.

Diverticulitis (the aggravation of diverticulosis)
Up to a quarter of people before 50 may already have one or more diverticula. This number grows to 50% after age 60. These diverticula result from large stools and straining caused by all of the factors listed above and namely, large stools and straining related to the excess use of dietary fiber.

Since most colonoscopies start after 50, the recommendation to hit on fiber immediately thereafter is particularly damaging to people already affected by diverticulosis. When large stools and fiber get trapped inside diverticula, they are likely to cause an inflammation of unprotected mucosa which may result in bleeding and severe pain related to ulceration, necrosis, or perforation.

YOUR ACTION: Do not use fiber and fiber laxatives following colonoscopy. The advice to use fiber is wrong and it is based on outdated and falsified information. Use Colorectal Recovery Kit instead to restore proper stool morphology without fiber.

Ulcerative colitis
The predisposition to ulcerative colitis — an inflammation and ulceration of the colon mucosa following colonoscopy is quite high because all the preconditions are there: mucosal inflammation, lack of protective bacteria, inadequate coagulation, poor healing, diarrhea, and excess use of fiber.
YOUR ACTION: It is easier to prevent than treat ulcerative colitis. Use Colorectal Recovery Kit to prevent its occurrence or relapse, particularly if you have a history of diarrhea and/or ulcerative colitis.

Crohn’s disease
Crohn’s disease is a condition similar to ulcerative colitis except its localization may happen anywhere along the gastrointestinal tract and it has a strong auto-immune component. The reasons behind it and preventive actions are similar to ulcerative colitis.

Formation of pre-cancerous polyps and cancers
I believe the genetic and ethnic aspects of colon cancer are highly exaggerated. Polyps and cancers — abnormal cellular growths — don’t just pop-up out of the blue. It literally “takes a village” to grow one. Just like oral cavities respond to chewing tobacco hours on end with oral cancer, so does the colon respond with polyps and cancers to long-term assault of the large intestine with fiber, fermentation, large stools, straining, antibiotics and pollutants.

YOUR ACTION: Use Colorectal Recovery Kit to wean yourself from fiber dependence, to restore intestinal flora, to maintain small stools and to prevent straining. Give your colon health the same attention you are giving to cutting your hair and brushing your teeth. I’ve yet to hear about “teeth cancer” or “hair cancer,” but people are dying from colorectal cancer left and right.

I realize the following two questions may be bugging you: (1) why aren’t the complications described in this guide discussed with patients in advance of the screening? (2) Is it because doctors don’t know? 
I believe there are three factors behind this particular health scare:

  • First, you aren’t likely to encounter your endoscopist ever again. If the colonoscopy results are abnormal, you’ll be immediately referred to the GI surgeon or oncologist. So, yes, in essence, they may not know or want to know what’s happening afterwards.
  • Second, many people undergoing colonoscopy may already have some or all of the symptoms and conditions that follow a colonoscopy, such as antibiotic-induced disbacteriosis, irritable bowel syndrome, bloating, flatulence, fiber dependency, hemorrhoids, straining and so on. So they just return to their “normal” state without connecting one and two.
  • Finally, colonoscopies are an extremely profitable business. A mid-volume endoscopy practice with just a single physician may gross between $4 and $6 million annually. Why ruin a good business by focusing on a few side effects with patients you’ll never see again, especially when everyone and their uncle believes that a colonoscopy saves lives?

Regardless of these reasons — some sinister, some stupid, some inadvertent to this situation — you now have the knowledge of what’s causing them, how to avoid them and what to do about it.
What to do when you can’t just say “no…”

In certain cases, colonoscopies are unavoidable, and, perhaps, life-saving. To protect yourself from unnecessary side effects, keep the following points in mind::

  • Avoid abdominal computer tomography at any cost because it increases your risk of developing any cancer from radiation equal to the exposure on the outskirts of Hiroshima on August 6th of 1945.
  • When push comes to shove, choose lesser evil. Perform a conventional colonoscopy only if you have a good reason for getting screened for colon cancer.
  • Avoid haphazard, fast-track screenings. The difference in polyp detection from a good doctor to a bad one is up to ten times, while the cost is exactly the same [link]. So seek out a reputable specialist, who takes time to do it right. Otherwise, what’s the point?
  • Weigh up your odds against the risks. If you aren’t in a high risk group, and do nothing, there is a 95% to 97.5% (perhaps, even less) chance that you’ll never experience colon cancer, and a 100% chance that you will not face colonoscopy-related side effects described on this site.
  • Restore colon ecology properly after a colonoscopy. This is a particularly important point, otherwise you increase your risk of developing colon cancer even more, regardless of your initial risk. I explain how to do it on the Restoring Intestinal Flora page.
  • Eliminate all avoidable causes of colon cancer, particularly if you are in a high-risk group. You’ll find all necessary recommendations on the Colorectal Cancer Risk Factors page.
  • Get off processed fiber and fiber laxatives. The commonplace advice to consume dietary fiber and use fiber laxatives to prevent colon cancer is flat out wrong, at least if you believe the good doctors from the Harvard School of Public Health whom I already cited here., If you are a physician or epidemiologist, and would like to get additional information about the perils of cancer (not just colorectal) screening, I recommend reading Dr. Gilbert Welch’s book entitled Should I Be Tested for Cancer  The answer to this question is quite self-evident from the subtitle: “Maybe Not and Here’s Why!

Dr. Welsh — an ultimate insider — presents a good number of compelling reasons to explain why, in his own words “…cancer screening can do more harm than good”, and supports his analysis with detailed epidemiological data.
According to Dr. Welch, the fear-mongering involved and risk of testing for other cancers are just as bad as for colon cancer. What else is new — where there is easy money to be made, victims are inevitable.

Author’s commentaries

As you can see, a screening colonoscopy isn’t the panacea it’s purported to be. Be mindful of the risks; removing the causes of colon cancer should come first. And whether you do it or don’t do it, it shouldn’t be based on Ms. Couric’s or my opinion, but on your doctor’s weighted recommendation and/or risks factors discussedhere.

Despite being well past 50, and in the high risk group for colorectal cancer, neither myself nor my wife Tatyana have ever been screened for colorectal cancer. We place more trust in functional nutrition and God’s will than in “just in case” testing.

If and when we will take any test, we first must be darn sure that it’s absolutely necessary. But as long as nothing hurts, we aren’t into playing Russian roulette. I learned this rule a long time ago from an inside joke popular among physicians: “Should we treat him, or let him live?

It isn’t as cynical as it may sound — medical doctors realize better than most that all medical procedures are inherently risky. Therefore, please don’t interpret my analysis of screening colonoscopies as “Don’t do it!”, but as “Don’t overdo it!

Finally, if you do decide to get screened, at the very least you should restore intestinal flora after the procedure, as explained here. Otherwise you may be increasing your risk of developing new polyps and colorectal cancer long before the next screening is due in five or ten years, depending on your risk profile.