When a Colonoscopy Causes Post-Procedure Bleeding

A colonoscopy is an exam that allows your doctor to look for telltale signs of trouble in your colon, such as swollen tissue, ulcers, polyps or tumors. It's an outpatient procedure that could potentially be life-saving.

Still, the procedure is invasive — it requires the physician to insert a flexible "scope" into your rectum and colon — and therefore not entirely without risk. One particular risk is bleeding after the colonoscopy. Not all cases of post-colonoscopy bleeding indicate a serious problem, however, and less than 1 percent of patients experience any complications after the procedure, according to Columbia University Irving Medical Center.

​Read more:​ The Potential Side Effects of a Colonoscopy Procedure

"After a colonoscopy, particularly if a polyp has been removed, it is not unusual to experience a small amount of bleeding — generally about a tablespoon or so — in the first couple of days after the procedure," says Andrew Chan, MD, MPH, gastroenterologist, director of the Gastroenterology Training Program at Massachusetts General Hospital and professor of medicine at Harvard Medical School.

Mayo Clinic researchers add that some degree of bleeding after a colonoscopy might occur if the physician conducting the procedure spots a potentially troubling area and decides to take a tissue sample for further post-procedure testing. Such bleeding is typically minimal and not usually a cause for alarm.

Another trigger for a small amount of post-op blood could be certain types of medications that are generally known to increase bleeding risk. Aspirin, often taken by people with heart disease, is one common example.

"Generally, we ask patients to continue their aspirin before and after their colonoscopy," says Dr. Chan. "But patients should ask their physicians about continuing other blood-thinning medications."

Experts at the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) advise people who are going to have a colonoscopy to inform their doctors about all prescription and over-the-counter medications they're taking, as well as any vitamins and supplements.

In addition to aspirin, the NIDDK highlights arthritis drugs, diabetes drugs and anti-inflammatories such as ibuprofen and naproxen as possible concerns. Your doctor can help you decide which medications to stop taking, if any.

Apart from that, however, Dr. Chan and the Columbia University experts concur that severe and persistent bleeding is not normal and should be addressed immediately. "If there is significant amount of blood," cautions Dr. Chan, "then patients should contact their physicians right away." It could be a sign of a tissue tear or colon perforation.

But how much bleeding is too much? "A 'lot' usually means blood fills the toilet bowl, or there are many consecutive bowel movements which produce blood, especially without stool," he explains.

​Read more:​ What to Eat After a Colonoscopy

According to researchers at Harvard Health Publishing, roughly 140,000 Americans were diagnosed with colorectal cancer in the past year, and the disease claimed the lives of some 50,000 men and women. But, they say, if everyone underwent regular colon cancer screening, about 60 percent of those deaths could be prevented.

For those at average risk, Harvard experts say, colonoscopies should be a once-a-decade affair starting at age 50. Why 50? Because according to the Centers for Disease Control and Prevention, 90 percent of all new cases of colorectal cancer in the United States occur among people 50 and older.

In some cases, however, earlier and more frequent screenings may be recommended. For example, African-Americans, smokers, people with obesity and those with a family history of colon cancer are considered to be at higher-than-average risk for colorectal cancer and are often encouraged to start getting screened before turning 50.