A 67-year-old man comes to the office due to a 2-day history of diarrhea and left-sided abdominal pain. The patient was seen in the emergency department 10 days ago due to left lower quadrant pain and low-grade fever; CT scan showed sigmoid diverticulitis. He was given amoxicillin–clavulanic acid therapy for 7 days. The patient completed the course of antibiotic therapy with good resolution of symptoms. However, over the past 2 days, he has developed left-sided abdominal pain and multiple watery stools. Temperature is 37 C (98.6 F), blood pressure is 120/80 mm Hg, and pulse is 98/min. Abdominal examination shows left-sided tenderness without rebound, rigidity, or guarding. Which of the following is the most appropriate empiric therapy while studies are pending in this patient?
Show Explanatory Sources
This patient's new-onset watery stools and abdominal pain immediately following a course of antibiotics are most concerning for Clostridioides difficile infection (CDI). Profuse watery diarrhea (≥3 loose stools/24 hr) is the hallmark symptom of CDI, which is suspected particularly when major risk factors (eg, recent antibiotic use, advanced age [>65]) for CDI are present. Other common features include abdominal pain and leukocytosis; fever is present in approximately 15% of patients.
While confirmatory stool testing is pending, empiric antibiotic therapy with either oral fidaxomicin or vancomycin is appropriate for most patients. This includes patients, such as this one, with nonsevere or severe disease; the distinction is typically based on the degree of leukocytosis (severe: >15,000/mm3) or the serum creatinine elevation (severe: >1.5 mg/dL).
For patients who develop fulminant CDI with hypotension/shock or ileus/megacolon, oral therapy is often supplemented with intravenous metronidazole. This bolsters the delivery of antimicrobial therapy to the inflamed colon, especially if impaired transit of oral antibiotic therapy is present due to ileus.
(Choice B) Levofloxacin, usually with metronidazole, may be used for the outpatient treatment of diverticulitis. Although diverticulitis can cause left-sided abdominal pain and a change in bowel habits (constipation, diarrhea), profuse watery diarrhea is uncommon, and other symptoms (eg, nausea/vomiting, low-grade fever, urinary frequency) are often present. This patient's recent diverticulitis resolved with treatment; his new-onset, watery diarrhea following antibiotic therapy is most concerning for CDI.
(Choice C) Although this patient has diarrhea, an antimotility agent (eg, loperamide) should not be given empirically; if CDI is present, it may cause bacterial toxins to be retained in the colon, increasing the risk for toxic megacolon. Once antibiotic therapy for CDI is initiated, an antimotility agent may be considered.
(Choice D) Metronidazole was once a first-line agent for the treatment of CDI but now is considered only if fidaxomicin or vancomycin are unavailable (and only for nonsevere disease) because it is less effective for achieving a symptomatic cure of CDI.
(Choice E) Neomycin, typically with rifaximin, may be used to treat small intestinal bacterial overgrowth (SIBO). Although SIBO can cause watery diarrhea and abdominal pain, bloating and flatulence are also typically present. In addition, SIBO is unlikely following a course of amoxicillin–clavulanic acid, an alternate treatment.
Educational objective:
Oral fidaxomicin or vancomycin is used to treat Clostridioides difficile infection in most patients, including those with nonsevere or severe disease.