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Harvard Medical School
Complications are rare. One possible complication is aspiration (accidentally inhaling saliva into the lungs), which can cause pneumonia. If a biopsy is taken, or if the endoscope injures the wall of the esophagus or stomach, it can cause bleeding. If severe, internal bleeding can require a transfusion. In rare cases, perforation of the lining of the stomach, esophagus, or intestine can also occur, requiring surgery. The sedative given can sometimes cause an allergic reaction.