Snapshot A 44-year-old woman presents to the emergency room for watery diarrhea for 3 days. She was recently admitted to the hospital for a urinary tract infection and discharged to finish a course of ampicillin. She completed this course 2 weeks ago. She reports seeing occasional blood in her diarrhea, but that it has mostly been watery. She also reports having anorexia, malaise, and cramping abdominal pain. On physical exam, she is dehydrated and has tenderness to palpation in the abdomen. She is found with a marked leukocytosis and started on fluids as well as oral vancomycin. Introduction Classification login to view 4 more bullets Epidemiology Incidence login to view 1 more bullet Risk factors login to view 8 more bullets ETIOLOGY Pathogenesis login to view 4 more bullets Presentation Symptoms login to view 6 more bullets Physical exam login to view 4 more bullets Imaging Abdominal radiography login to view 5 more bullets Sigmoidoscopy/colonoscopy login to view 5 more bullets Abdominal computed tomography (CT) login to view 6 more bullets Studies Labs login to view 7 more bullets Making the diagnosis login to view 1 more bullet Differential Ulcerative colitis login to view 3 more bullets Crohn disease login to view 4 more bullets Treatment Management approach login to view 2 more bullets Medical login to view 19 more bullets Complications Colonic perforation login to view 1 more bullet Toxic megacolon login to view 1 more bullet Prognosis Relapse occurs in ~20% of patients