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 Clostridium difficile anaerobic gram + rod produces 2 toxins that bind to intestinal mucosal cells forms heat-resistant spores Epidemiology Incidence common Risk factors recent antibiotics use clindamycin ampicillin cephalosporins fluoroquinolones proton-pump inhibitors recent hospitalization advanced age ETIOLOGY Pathogenesis causes a pseudomembranous colitis and diarrhea characterized by yellow-white plaques in intestinal mucosa toxin A is an enterotoxin that binds to the intestinal brush border toxin B is a cytotoxin and depolymerizes actin, disrupting the cytoskeleton Presentation Symptoms crampy abdominal pain anorexia malaise diarrhea typically watery diarrhea occasionally may be bloody but without frank blood Physical exam fever dehydration abdominal tenderness to palpation rebound tenderness in severe cases Imaging Abdominal radiography indications if toxic megacolon is suspected for quick diagnosis and assess for early intervention findings dilated colon Sigmoidoscopy/colonoscopy indication if laboratory evaluation is unclear not always necessary findings pseudomembranes on intestinal mucosa Abdominal computed tomography (CT) indication suspicion for pseudomembranous colitis findings marked thickening of the colonic wall irregularity of bowel wall pericolonic stranding Studies Labs ↑ white blood cells ↓ hypoalbuminemia ↑ lactate diagnostic tests of the stool polymerase chain reaction for the organism detection of toxin + fecal leukocytes Making the diagnosis based on clinical presentation and stool studies Differential Ulcerative colitis distinguishing factors typically presents with bloody diarrhea can also present with dermatologic manifestations such as erythema nodosum Crohn disease distinguishing factors can be bloody or nonbloody can present with fistulas can also present with dermatologic manifestations such as erythema nodosum Treatment Management approach 10-day course of antibiotics discontinue inciting antibiotics or other drugs Medical oral vancomycin indications first line often used in lieu of fidaxomicin due to cost/availability fidaxomicin indication first line according to new 2021 Infectious Disease Society of America guidelines however, use is limited by high cost and limited availability severe cases recurrent cases oral metronidazole indications used as an alternative if vancomycin or fidaxomicin are not available used in addition to vancomycin if patients are refractory to monotherapy contraindicated in the elderly fecal microbiota transplant indication recurrent cases Complications Colonic perforation occurs in small percentage of patients Toxic megacolon occurs in small percentage of patients Prognosis Relapse occurs in ~20% of patients