A new study has found that complications of endoscopic procedures may be more common than doctors report.

Researchers from Beth Israel Deaconess Medical Center in Boston analyzed more than 18,000 procedures, including colonoscopies and upper-gastrointestinal endoscopies. According to electronic medical records, 134 emergency room visits and 76 hospitalizations occurred within 2 weeks of the procedures.

Results indicated that about 1 percent of all procedures resulted in complications severe enough to warrant a trip to the emergency room – a higher rate than estimated by adverse event reports, according to the New York Times.

“A lot of low-level complications were flying under the radar,” said Dr. Daniel Leffler, the paper’s lead author and an assistant professor of medicine at Harvard. “A lot of physicians wouldn’t consider abdominal pain a complication, but at the same time, the person went to the E.R. and missed work, so it was a significant burden to the patient and to the health care system.”

Endoscopy is often the final step in celiac disease diagnosis. It identifies signs of intestinal damage that result when the autoimmune disorder is left untreated.