This patient's abdominal pain following colonoscopy with biopsies is concerning for perforation at the polypectomy site. Perforation can occur due to direct mechanical trauma from the colonoscope, barotrauma from the colonoscopy pressure, or electrocautery injury during polypectomy. Screening colonoscopy has <0.1% risk of perforation, but interventions (eg, dilatation) can increase the rate up to 18%. Perforations can be retroperitoneal if involving the ascending or descending colon or the splenic and hepatic flexures, or intraperitoneal if the transverse or sigmoid colon is involved.
Patients with perforations typically have abdominal pain or distension and may also have fever and chest or scapular pain. Peritoneal signs (eg, rebound tenderness, decreased bowel sounds, abdominal wall rigidity) eventually develop. Immediate abdominal x-ray (plain and upright or lateral decubitus) and upright chest x-ray should be obtained to look for free air.
Patients in whom there is a high clinical suspicion for perforation but with negative x-rays should undergo abdominal and pelvic CT scan with water-soluble contrast (eg, Gastrografin). CT scan with contrast is more sensitive than plain films for detecting extraluminal air and subtle perforation. Management involves broad-spectrum antibiotics and surgical consultation. Noncontrast CT scan may miss subtle perforations and is not recommended.