A study has found that rates of infection following colonoscopy and endoscopy are far higher than previously realized.

Infection risks following colonoscopies and upper-GI endoscopies may be as much as 100 times higher than previously believed, according to new research from Johns Hopkins.

The study, which was published in Gut, found that rates of infection after procedures performed at some outpatient facilities in the United States exceeded the rates estimated by previous research.

Susan Hutfless, PhD, assistant professor of medicine at Johns Hopkins University in Baltimore, and a team of researchers examined medical insurance data from 2014 to determine these post-procedure infection risks.

They looked at the insurance payer database for six states: California, Florida, Georgia, Nebraska, New York, and Vermont.

From the information, they determined which patients underwent one of these common procedures in facilities called ambulatory surgery centers (ASCs) and then developed a bacterial infection within 7 to 30 days.

They found that bacterial infections, such as E. coli and Klebsiella, occur at the following rates:

  • 1 in 1000 people after screening colonoscopies
  • 1.6 in 1000 people after nonscreening colonoscopies
  • 3 in 1000 people after esophagogastroduodenoscopies (EGDs), or upper-GI endoscopies

“Though patients are routinely told that common endoscopic procedures are safe,” Hutfless said in a statement, “we found that post-endoscopic infections are more common than we thought, and that they vary widely from one ASC facility to another.”

The study did not definitively find that the colonoscopies and endoscopies caused the infections, just that they occurred shortly after the procedure.

Each year, more than 15 million colonoscopies and seven million EGDs are performed in the United States. Both procedures are considered routine and low risk.

During these procedures, a doctor or endoscopist will use an endoscope — a reusable lighted and flexible tube — to view inside the gastrointestinal (GI) tract. Both of these procedures are used to screen for cancer or remove potentially precancerous polyps. They may also be used to diagnose causes of symptoms such as abdominal pain, heartburn, and swallowing issues.

Hutfless wanted to know how many patients later developed bacterial infections, so she and the team looked for infection-related emergency room visits or inpatient admissions within a week or month following the colonoscopy or EGD.

Previously, researchers believed that the infection rate was about 1 in 1 million. However, these findings cast doubt on that low-risk estimate.

In fact, the researchers also found that patients who had been hospitalized before undergoing either a colonoscopy or EGD were at an even greater risk of developing an infection.

For those patients, 45 in 1000 patients who had been hospitalized at least 30 days before their colonoscopy developed an infection. Infection-related hospitalizations for EGDs were at 59 in 1000.

ASCs are outpatient facilities where patients can have minor procedures or tests conducted without going into a hospital setting. ASCs have been around for more than four decades, but their popularity has increased greatly in the last 20 years as patients have looked for less expensive, more convenient, and more efficient alternatives to traditional hospital settings.

Many ASCs in the United States are owned and operated entirely by physicians. Others may be affiliated directly with hospitals and larger health systems, or they may be owned in small or large parts by those organizations.

That setup may help account for many of the undiscovered links between the procedures and infections.

Some ASCs lack electronic medical record systems, and facilities not associated with a hospital may not be able to connect their records systems with hospital emergency departments.

That means these facilities are unlikely to learn of their patients’ post-endoscopy infection.

“If they don’t know their patients are developing these serious infections, they’re not motivated to improve their infection control,” Hutfless said in a statement.

Hutfless and her team found that facilities with the largest number of procedures had the lowest rates of infections. The number of infections also varied greatly between facilities However, infection rates at some of the ASCs were more than 100 times higher than expected.

Colonoscopies are frequently recommended to patients as regular screening procedures for colon cancer.

“The U.S. Preventive Services Task Force, American Cancer Association, and American Gastroenterological Association all recommend screening for colon cancer by age 45 to 50,” says Dr. Daniel Freedberg, gastroenterologist and assistant professor of medicine at Columbia University Medical Center.

Dr. David B. Samadi, chairman of urology and chief of robotic surgery at Lenox Hill Hospital in New York, expresses caution about this study’s results and believes additional research can help doctors and facilities better understand the infections before changes take place.

“In general, what we are finding is that centers with high volume have a better outcome and lower rate of infection, which is true about other surgical cases as well,” said Samadi, the host of the radio show “Men’s Health with Dr. Samadi.” “I would be very interested in seeing a more comprehensive study with a much larger pool of patients to make sure it is not a random outcome.”

Likewise, Freedberg suggests that the research doesn’t make clear that the infection is a result of the procedure and not some other issue.

“The study used insurance claims data to look at health events that occurred after colonoscopy, but it should be kept in mind that simply because an adverse health event occurred after a colonoscopy, it does not necessarily mean that the colonoscopy caused the adverse event,” Freedberg says. “Some of these infections probably would have occurred regardless of whether or not the patient had a colonoscopy, but we cannot be certain how many.”

If you’re scheduled for a one of these procedures soon, Samadi suggests you do your research before you pick a doctor and facility.

If you’ve had one of these procedures and develop fever, chills, abdominal pain, constipation, diarrhea, or nausea, report these symptoms to the facility where you had the procedure and to the doctor who typically treats you, Samadi suggests. It’s important you get treatment, but it’s also important to let the facility know of this complication so they can improve their complication-prevention measures.