Clostridioides difficile infection
Clostridioides difficile infection is toxin-mediated colitis that follows disruption of normal colonic flora, most often by antibiotics, and ranges from watery diarrhea to fulminant colitis with shock, ileus, or megacolon. Diagnosis rests on unformed stool testing (NAAT and/or toxin EIA) in a patient with three or more unformed stools in 24 hours, and treatment is chosen by IDSA/SHEA severity grade, oral vancomycin or fidaxomicin for 10 days, escalating to high-dose vancomycin plus IV metronidazole for fulminant disease.
- Topic reviewThe full article, organized the way the exam asks it.
- ABIM-format MCQsVignettes with an explanation for every wrong answer.
- Key factsThe numbers and thresholds worth memorizing, up front.
- AI tutorMedBrain answers the question you're stuck on.
What this article covers
- Overview
Definition: Clostridioides difficile infection (CDI) is toxin-mediated colitis that develops when antibiotic disruption of the normal colonic flora allows C.
- Epidemiology
Most common cause of health-care-associated infectious diarrhea in the United States; incidence rose sharply after 2000 with emergence of a hypervirulent, fluoroquinolone-associated strain, though…
- Risk factors
Recent antibiotic exposure: the strongest risk factor overall, especially clindamycin, fluoroquinolones, and other broad-spectrum agents active against anaerobic flora but not against C.
- Pathophysiology
Flora disruption is the initiating event: antibiotics (or, less often, chemotherapy) suppress normal colonic microbiota, removing colonization resistance against C.
- Clinical features
Watery diarrhea: the hallmark, typically three or more unformed stools in 24 hours; grossly bloody stool is uncommon.
- Differential diagnosis
Inflammatory bowel disease flare: chronic or bloody diarrhea with continuous, symmetric rectal-onset mucosal inflammation on colonoscopy rather than patchy pseudomembranes; C.
- Diagnosis
Establish the diagnosis by unformed stool testing in a patient with three or more unexplained unformed stools in 24 hours who is not taking laxatives.
- Management
Stop the inciting antibiotic whenever possible as the first step in every patient, regardless of severity.
- Complications
Fulminant colitis with shock and multiorgan failure: the most life-threatening progression, driving urgent surgical evaluation.
- Prognosis
Outcome tracks severity grade: nonsevere disease generally responds well to first-line oral therapy, while fulminant disease with shock, ileus, or megacolon carries substantially higher morbidity and often requires colectomy.
- Prevention
Antibiotic stewardship is the primary preventive measure: minimizing unnecessary use of high-risk agents (clindamycin, fluoroquinolones, broad-spectrum cephalosporins and penicillins) reduces incidence at the population level.
Read the whole article
Subscribing to Internal Medicine opens every article, the full question bank and MedBrain, on the web, iPhone and Android.
Related articles
- Diarrhea
Diarrhea is three or more unformed stools daily, split by duration into acute (under 14 days, usually infectious), persistent (14 to 30 days, often parasitic), and chronic (over 30 days, usually noninfectious), and by mechanism into osmotic, secretory, inflammatory, malabsorptive, and motility diarrhea. Acute diarrhea is managed with rehydration and tested only when red-flag features are present, while chronic diarrhea is worked up by mechanism using stool studies, celiac serology, fecal calprotectin, and endoscopy.
- Sepsis
Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection, identified by an acute rise in SOFA score of 2 points or more in a patient with known or suspected infection. Survival depends on recognizing the pattern early and completing the hour-1 bundle: lactate, blood cultures before antibiotics, broad-spectrum antibiotics such as cefepime 2 g IV every 8 hours, and 30 mL/kg crystalloid for hypotension or a lactate of 4 mmol/L or higher.
- Ischemic colitis
Ischemic colitis is the most common form of gastrointestinal ischemia, caused by a nonocclusive low-flow state in colonic microvessels that classically injures the watershed splenic flexure and rectosigmoid junction. Most cases are mild and self-limited with supportive care, but segmental CT thickening with peritoneal signs, pneumatosis, or gangrene demands emergent surgery rather than antibiotics alone.
- Ulcerative colitis
Ulcerative colitis is a chronic immune-mediated disease of continuous mucosal inflammation that begins in the rectum and extends proximally through the colon, presenting with bloody diarrhea and tenesmus and confirmed by colonoscopy with biopsy. Treatment is stepped by extent and severity from 5-aminosalicylates through corticosteroids, immunomodulators, and biologics, with acute severe disease requiring IV corticosteroids and medical or surgical rescue, and colectomy remains curative.
- Microscopic colitis
Microscopic colitis is a cause of chronic watery, non-bloody diarrhea in older women with a grossly normal colonoscopy, diagnosed only by random colon biopsy showing lymphocytic or collagenous histology. Management starts with stopping culprit drugs and antidiarrheals, then oral budesonide for induction and, if needed, maintenance.