A 55-year-old woman with a history of chronic constipation and previous hysterectomy undergoes a colonoscopy. The procedure is challenging due to a tortuous and redundant colon. A 7-mm sessile polyp in the transverse colon is removed with a cold snare. She returns to the emergency department 10 hours later with diffuse abdominal pain. Initial evaluation reveals that she is afebrile, with a heart rate of 115 beats/min and blood pressure of 90/60 mm Hg. On examination, she is mildly distended with diffuse mild tenderness. Upright chest radiography findings are unremarkable. Her white blood cell count is 12,000/μL (12×10⁹/L) and hemoglobin is 7 g/dL (70 g/L). Computed tomography is pending. What is the likely cause of her presentation?