Roughly 20 million colonoscopies are performed in the United States every year. For most people, it's a routine screening. But when a reusable colonoscope hasn't been cleaned properly between patients — or when its design prevents proper cleaning — a routine screening can turn into a life-threatening infection.
Many patients who get sick after a colonoscopy never connect their illness to the procedure. The symptoms show up days or weeks later, and doctors often attribute them to other causes. Here's what you need to know.
Colonoscopy is the most common endoscopic procedure in the United States, with roughly 20 million procedures performed every year. It is the gold-standard colon cancer screening tool, and the American Cancer Society recommends colonoscopy starting at age 45 for average-risk adults.
That volume is what makes colonoscope contamination such a serious public-health problem. Even a very small contamination rate translates into a very large number of potentially infected patients. If just one-tenth of one percent of colonoscopies transmitted a meaningful infection, that would be 20,000 cases per year. Published studies suggest the real contamination rate is much higher than that.
The scale is one reason the FDA, CDC, and major medical organizations have focused so much attention on endoscope reprocessing — and one reason product liability cases against scope manufacturers have expanded beyond ERCP duodenoscopes alone.
A 2018 peer-reviewed study led by Cori L. Ofstead and colleagues, published in the American Journal of Infection Control, examined reusable colonoscopes after they had been fully reprocessed using standard hospital protocols. The researchers found visible residue on the majority of scopes and cultured viable bacteria from a substantial number of them.
The findings added to a growing body of evidence that standard colonoscope reprocessing is not consistently effective, even at well-resourced hospitals following manufacturer instructions.
Routine does not mean safe. The enormous volume of colonoscopies means that even rare contamination events translate into real injuries. Most of those injuries are never traced back to the scope because patients, primary-care doctors, and emergency rooms aren't trained to connect the dots.
A colonoscope is a long, flexible scope with an inch-plus-wide outer diameter and several narrow internal channels running its full length. Each channel serves a different purpose: one carries air and water, one provides suction, and one is a working channel for instruments like biopsy forceps and snares.
During a colonoscopy, those narrow channels become coated with stool, blood, tissue, and mucus from the patient's colon — all of which carry large populations of bacteria. When the scope is cleaned, technicians push brushes through the channels and then immerse the scope in liquid disinfectant.
When brushes don't reach every surface, when the channels aren't perfectly dried before storage, or when biofilm has built up inside the channel walls, live bacteria can survive to the next patient.
Over many cycles of use, bacteria can form a biofilm inside the channels — a thin, protective layer that shields bacteria from disinfectant. Once biofilm forms, normal reprocessing becomes dramatically less effective at eliminating pathogens.
Detecting biofilm requires specialized testing that most hospitals don't routinely perform. A scope that looks clean and that just finished a full reprocessing cycle can still be coated on the inside with live bacteria and the biofilm protecting them.
These are the conditions that make it possible for a patient to walk into a gastroenterology clinic for a screening and walk out carrying a serious infection from a previous patient. Learn more about the mechanics of scope contamination and the hospital reprocessing failures that make it worse.
Published in the American Journal of Infection Control, this study examined colonoscopes and gastroscopes after full reprocessing using standard hospital protocols. The researchers found visible residue on the majority of scopes and confirmed viable bacterial contamination on a substantial fraction. The findings were consistent with earlier research showing that standard reprocessing does not reliably clean reusable endoscopes.
Ofstead CL, Heymann OL, Quick MR, Eiland JE, Wetzler HP. "Residual moisture and waterborne pathogens inside flexible endoscopes: Evidence from a multisite study of endoscope drying effectiveness." Am J Infect Control. 2018.
The American Society for Gastrointestinal Endoscopy issued updated guidance acknowledging that standard high-level disinfection had documented failure rates, and that additional measures — including more aggressive drying, better staff training, and surveillance culturing — were needed at endoscopy centers performing high volumes of procedures.
ASGE Standards of Practice Committee, "Multisociety guideline on reprocessing flexible GI endoscopes: 2018 update," Gastrointestinal Endoscopy.
The Association of periOperative Registered Nurses (AORN) publishes detailed guidelines for scope reprocessing that are used at hospitals across the country. These guidelines describe the many failure points in standard reprocessing — from manual cleaning to drying and storage — and acknowledge that full compliance is difficult to achieve in practice. When hospitals fall short of these standards, it can be evidence of negligence in a case.
AORN "Guideline for Processing Flexible Endoscopes" (most recent edition).
Scope-related infections rarely show up the day of the procedure. They show up days or weeks later — after the patient has gone home, gotten back to their routine, and largely stopped thinking about the colonoscopy. By the time the infection takes hold, nobody is asking whether the scope could be the cause.
A patient might show up at the emergency room with a fever, abdominal pain, and a confused look on their face. The ER doctor sees an infection, orders antibiotics, and treats the symptoms. The colonoscopy is not in the story. The underlying cause — a contaminated scope — is never investigated.
This is why reviewing your records matters. A medical-legal expert looking through your history can identify whether the infection's timeline, pathogen, and resistance pattern are consistent with a scope-borne infection. That kind of review is not part of a typical emergency-room workup — but it is exactly the kind of review we do on every intake.
If you developed any of the following within about 30 days of a colonoscopy, a contaminated scope should be considered as a possible cause. These patterns alone do not prove the scope was the source — but they are strong enough reasons to have your records reviewed.
Full symptom list available on the infection symptoms page. If any of these ring a bell, it's worth 15 minutes to have the records reviewed.
Answers to the most common questions from colonoscopy patients who suspect a scope may have been the cause of their infection.
Yes. Colonoscopes are reusable scopes that pass through one patient's colon and then, after cleaning, through the next patient's. Studies examining scopes after standard reprocessing have found bacterial contamination rates between roughly 1% and, in some studies, more than 30%, depending on the method and what pathogens were tested for. The colonoscope does not have an elevator mechanism (which is what makes ERCP duodenoscopes the highest-risk scope), but it still has long, narrow internal channels that are difficult to clean, and it has been directly linked to pathogen transmission in multiple peer-reviewed studies.
Nobody knows the real number because most infections never get traced back to the procedure. What we do know is that even if only one-tenth of one percent of colonoscopies transmitted a meaningful infection, that would be 20,000 cases a year in the U.S. alone. Published studies suggest the true rate of post-reprocessing scope contamination is much higher than that. Underreporting is the rule, not the exception.
Yes, especially if the infection appeared within 30 days of the colonoscopy, required hospitalization, involved an unexpected bacteria species, or was resistant to common antibiotics. Many doctors are not trained to look for scope contamination as a cause, and most hospitals do not proactively notify patients when a scope has been flagged for potential contamination. A second opinion from a medical-legal expert — in our firm, Herb Borroto, M.D., J.D. — costs you nothing and can change the picture significantly.
Documented pathogens transmitted through contaminated colonoscopes include Pseudomonas aeruginosa, E. coli (including drug-resistant strains), Klebsiella pneumoniae, Salmonella, Hepatitis B and C (in older studies), and multidrug-resistant organisms like ESBL-producing bacteria. Sepsis, bloodstream infections, and unexplained bacteremia in the weeks after a colonoscopy are the kinds of findings that should trigger closer investigation.
Every factual claim on this page is supported by a verifiable public source. Click any source below to read the original.
If you developed a serious infection in the weeks after a colonoscopy, a contaminated scope may be why. A free, confidential case review with our team takes about 15 minutes. No Fees Unless We Recover Money for You.
