Patient: Female, 72-year-old Final Diagnosis: Mesenteric hematoma Symptoms: Abdominal pain • bloating • nausea • vomiting Medication: — Clinical Procedure: Screening colonoscopy • followed by open laparoscopy with the evacuation of a hematoma Specialty: Gastroenterology and Hepatology • Surgery Objective: Diagnostic/therapeutic accidents Background: We report the case of a patient undergoing a colonoscopy during which pressure applied on the abdomen by a nurse assisting in the procedure caused an extraluminal mesenteric tear. Mesenteric tears can be life-threating and need to be managed appropriately. This is the first case reported in the literature describing abdominal counter-pressure applied in the endoscopic procedure room as the cause of traumatic bowel injury. Case Report: A 72-year-old woman presented for a screening colonoscopy. Advancement of the colonoscope became so difficult that the procedure was temporarily aborted. To reduce looping of the colonoscope, the nurse assistant applied a forceful two-handed counter-pressure maneuver upon the abdomen to help the endoscopist advance the colonoscope to the cecum. After the procedure, the patient complained of abdominal pain and nausea. A CT scan of the abdomen showed a hematoma abutting the anterior abdominal wall. Unfortunately, laparoscopic surgery was hastily recommended over conservative medical management. Approximately 500 mL of old blood was evacuated. The patient survived postoperative complications, including pneumonia, respiratory failure, and sepsis. Conclusions: Mesenteric tears are a rare but potentially life-threatening complication of colonoscopy. Post-colonoscopy patients with severe nausea, abdominal pain and/or distention, who fail to demonstrate free air in the abdomen, should have a CT scan with i.v. contrast to assess their condition. Hemodynamically stable patients should be managed with serial vitals and bedside observations, laboratory tests, imaging studies, fluid replenishment, and medication, to avoid unnecessary high-risk surgery. Abdominal counter-pressure applied safely during colonoscopy can reduce the risk of injury inherent in the procedure.