Snapshot A 71-year-old man with coronary artery disease, diabetes, chronic obstructive lung disease, lung cancer, and arthritis is admitted for septic arthritis of his right knee after a recent steroid injection. He undergoes treatment with antibiotics and incision and drainage of the right knee. He reports feeling better with good pain control with hydrocodone; however, on postoperative day 3, he develops acute abdominal distention that is slightly tender to palpation. Abdominal radiography demonstrates cecal dilation to 11 cm. Introduction Clinical definition acute dilation of the large intestine in the absence of mechanical obstruction, also known as acute colonic pseudo-obstruction (ACPO) most often involves right colon and cecum Associated conditions hypothyroidism spinal cord injury Epidemiology Often in the elderly Risk factors narcotics anticholinergics recent surgery sepsis malignancy ETIOLOGY Pathogenesis mechanism unknown possibly due to autonomic nervous system dysfunction Presentation Symptoms bloating abdominal pain nausea and vomiting Physical exam abdominal distention abdomen tender to palpation fever IMAGING Diagnostic testing abdominal computed tomography scan diagnostic test rule out mechanical obstruction abdominal radiography screening test and for serial monitoring massively dilated cecum and right colon with decompression near splenic flexure Differential Toxic megacolon distinguishing factors associated severe colitis systemic toxicity such as tachycardia, fever, and altered mental status Large bowel obstruction distinguishing factor mechanical obstruction present Treatment First line discontinue offending medications conservative care intravenous fluids and electrolyte repletion nasogastric tube decompression Second line neostigmine if no resolution with 24-48 hours of conservative care atropine for possible bradyarrhythmia Third line colonoscopic decompression if no resolution after neostigmine Fourth line cecostomy if no resolution after colonoscopic decompression Complications Ischemic colitis Intestinal perforation Volvulus