Colonoscopies and Infection: Risk, Symptoms, Treatment

A colonoscopy is a procedure that’s used to look inside the colon (large intestine). A flexible tube with a light and a camera on the end is inserted into the anus and up through the rectum and the large intestine.

This test is done to screen for colon cancer and as a way to make a diagnosis of various other digestive conditions. It is a necessary and safe procedure.

In rare cases, a bacterial infection is possible after having a colonoscopy. While it’s not likely to happen, it’s good to know what the signs and symptoms are, which are covered in this article.

Preparing equipment for colonoscopy

Chun han / Getty Images

Infection Rates After Colonoscopy

The rate of infection in the digestive system after having a colonoscopy is low. 

One study included 112,543 people who had either colonoscopy or sigmoidoscopy (which looks at the lower part of the colon with a flexible viewing tube). The number of people who had an infection within 30 days after the procedure was noted. The overall rate was found to be 0.37%.

The infection rates broken out by procedure were:

  • Colonoscopy without invasive intervention (such as polyp removal): 0.41 %
  • Sigmoidoscopy without invasive intervention: 0.25 %
  • Endoscopic biopsy (a sample of tissue is removed during the test for testing): 0.28%
  • Endoscopic polypectomy (removal of a polyp during the test): 0.26%

Treatments During Colonoscopy

Treatments can be done during a colonoscopy, which might be called an invasive intervention" The most common of these is the removal of a polyp, which is a growth on the inside of the colon. Removing a polyp is important to prevent colon cancer, but may cause some minor bleeding.

The types of infection that occurred were also varied. The most common infections were:

  • Diverticulitis (an infection involving the colon): 38%
  • Peritonitis (an infection of the inner wall of the abdomen): 26%
  • Appendicitis (an infection of the appendix): 13% 
  • Osteomyelitis (an infection of the bones): 8%
  • Pyogenic liver abscess (a pocket of fluid in the liver): 6%
  • Septic pulmonary embolism (an infection in the lungs): 2%

Symptoms of Infection After Colonoscopy

An infection that happens after a colonoscopy may cause signs and symptoms. When leaving after a colonoscopy, people will be given some guidance on what to look for and which symptoms are a reason to call a healthcare provider.

Symptoms of an infection after a colonoscopy could include one or more of the following:

Sepsis is a life-threatening infection. It occurs when an infection in the body gets into the bloodstream. It’s important to know the symptoms of sepsis because it needs to get treatment right away.

The symptoms of sepsis can include:

  • Fever, followed by hypothermia (low body temperature)
  • Sweating
  • Tachycardia (rapid heart rate)
  • Tachypnea (rapid breathing) 

When to See a Healthcare Provider

You will be given instructions on when to contact your healthcare provider after a colonoscopy. A certain amount of abdominal discomfort may be part of the recovery process. Some people will have intestinal gas and this may be uncomfortable until it can be passed.

When a polyp has been removed, there could be bleeding from the rectum. Polyps are the precursor to colon and rectal cancer. If one is found during a colonoscopy, it is usually removed, and a small amount of blood may pass out of the rectum afterward.

However, these symptoms shouldn’t be severe, and they should go away within a day or so. If symptoms go on for too long or are really troublesome, it’s time to contact a healthcare provider.

Symptoms to watch for after a colonoscopy include:

  • Abdominal pain or cramps, especially if it is worsening
  • Bleeding from the rectum that’s severe or that goes on for too long
  • Chills
  • Fever 

Other Colonoscopy Risks and Complications

A colonoscopy is considered to be a safe procedure that can help save lives because it is used to screen for colon and rectal cancer. However, there are some risks.

Many colonoscopy procedures are given using sedation to help patients be more comfortable. Having a reaction to the anesthetic, such as an allergic reaction, which can happen any time anesthetic is used, is possible.

Aspiration pneumonia (lung infection due to inhaling secretions into the lungs) is another potential risk with anesthesia, but it is rare.

Another risk with a colonoscopy is getting a hole in the intestine (perforation). It happens if the tools used during a colonoscopy puncture the intestine. It is a rare occurrence that may cause abdominal pain and rectal bleeding.

Perforation might be treated during the colonoscopy, if it’s noticed at the time. or later. It is usually treated with either watchful waiting in the hospital or with surgery (in the case of larger perforations).

Post-polypectomy electrocoagulation syndrome is a condition that may cause pain after a polyp is removed during a colonoscopy. It’s caused by damage to the inner layers of the colon and leads to inflammation.

This syndrome is thought to only occur after between 0.003% and 0.1% of colonoscopies. It might happen more frequently with the removal of larger polyps. The symptoms are similar to those of perforation, with abdominal pain and bleeding.

Are Colonoscopies Safe?

A colonoscopy is considered to be a very safe procedure. Complications are uncommon to rare. The usefulness of the test in preventing and screening for colon and rectal cancer outweighs the risks.

There are some people for whom the benefits may not outweigh the risks. This might be true for people who are older, who have digestive conditions, or who have other conditions that may make the procedure carry more risk.

Reducing Risk

There are some risk factors for having an infection after a colonoscopy that aren’t something people can change. However, it’s good to know if your risk might be higher because of these things.

Some of the risk factors include:

  • Age: Being older than 70 years old or younger than 19 years old
  • Sex: Being male, as males had a higher rate of infection than females
  • Being hospitalized or having another gastrointestinal endoscopic procedure in the 30 days before the colonoscopy
  • Having inflammatory bowel disease (IBD, which includes Crohn’s disease or ulcerative colitis)

Data are lacking, but it appears that Black Americans and Native Americans may have higher rates of infection than White Americans after colonoscopy.

One way to lower risk is to ask questions. A colonoscopy is a safe procedure that saves lives by finding colon and rectal cancer. However, it’s worth first asking if the procedure is necessary, especially when there is a risk factor that can’t be changed (such as age), or if there is an alternative. 

Before having the procedure is also a good time to ask what kinds of safety precautions are in place to reduce risk, such as with cleaning the equipment. 

Lastly, patients can tell their gastroenterologist or another healthcare provider if they’re concerned about infections and ask what can be done to reduce the risk.

Questions to Ask

Endoscopy centers will have a staff member who cleans scopes. Scopes are usually tagged in some way as being clean after they've been processed. Peter Higgins, M.D., Ph.D., director of the IBD program at the University of Michigan, recommends asking these questions about the process include:

  • How are clean scopes identified?
  • How are the scopes monitored for bacteria after being cleaned?
  • How often are the scopes cleaned?


A colonoscopy is a safe procedure that can help detect colon and rectal cancer or help in diagnosing other diseases and conditions. Infections and other complications after having a colonoscopy are not common, but talking over any potential risk factors with a gastroenterologist may help patients feel more secure before the test.

A Word From Verywell

Getting a colonoscopy has become a rite of passage. It’s recommended that even people of average risk of colon and rectal cancer get a screening scope. It is a safe procedure, and the risks of any complications are low.

That doesn’t mean that patients shouldn’t ask questions, though. Being informed about all the parts of the procedure is important and will help make everything go smoother. 

Frequently Asked Questions

  • How long after a colonoscopy can complications arise?

    Many of the studies on complications after colonoscopy track patients for 30 days. If there’s a complication, it might be known soon after the colonoscopy because symptoms might begin in the days following the procedure. Some potential complications may start soon after the procedure but be longer-lasting, such as aspiration pneumonia. 

  • Is it normal to have abdominal pain two weeks after a colonoscopy?

    Abdominal pain that continues for two weeks after a colonoscopy is a reason to talk to a healthcare provider. Some people may have gas, bloating, or discomfort in the first few days after a colonoscopy. Having abdominal pain that goes on for longer than that could mean there is a problem that needs to be treated. 

  • Can you get sepsis from having a colonoscopy?

    Sepsis is an infection in the blood. If a person develops an infection after having a colonoscopy, sepsis could result. However, this is a rare occurrence. One study showed that the number of people who had bacteria in their blood after a colonoscopy was two or three per 100,000.

    Bacteria in the blood could lead to sepsis, but this doesn’t always happen. Therefore, the rate of sepsis would be even lower than that of people with bacteria in their blood. 

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Amber J. Tresca
Amber J. Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16.