An 80-year-old male presents with severe abdominal distention and, no bowel movements or passage of gas for 3 days, and recent onset of vomiting. He has a history of Parkinson’s disease and chronic constipation and lives in a nursing home. His medications include levodopa and benztropine, both of which he has been taking for several years. On examination, his temperature is 37 °C, heart rate 90/min, blood pressure 116/70 mmHg, and respiratory rate 22/min. He appears tachypneic but not acutely ill, and his mental status is unaltered from baseline. Lung examination reveals clear breath sounds bilaterally. His abdomen is severely distended and tympanitic without tenderness, surgical scars, or palpable hernias. Rectal examination demonstrates no stool, palpable masses, or strictures. Laboratory studies reveal metabolic panel with BUN 26 mg/dL (normal 7–21 mg/dL), creatinine 1.4 mg/dL (0.5–1.4 mg/dL), electrolytes within normal limits, white blood cell (WBC) count 6.8 × 103/μL (4.1–10.9 × 103/μL), and lactate 0.9 mmol/L (0.5–2.2 mmol/L). Arterial blood gas (ABG) shows pH 7.48, PaCO2 30 mmHg, PaO2 80 mmHg, HCO3 24 mEq/L, and oxygen saturation (SpO2) 99%. A plain upright abdominal radiograph shows a massively dilated loop of sigmoid colon with the apex pointing toward the right upper quadrant, consistent with the “coffee bean” or “bent inner tube” sign. An upright chest radiograph shows no free air under the diaphragm.