Pseudomembranous colitis (PMC), an inflammatory colitis largely caused by Clostridium difficile, is the most common cause of infectious health care-associated diarrhea. Its incidence has increased markedly in recent years, with immunocompromised and antibiotic-exposed patients being at high risk. Mortality from PMC is up to 3.5% in those infected.
C. difficile’s toxin A and toxin B work in concert to cause bowel cell death and pseudomembrane formation, leading to extensive diarrhea, fever, and cramping abdominal pain. Bowel loops can become dilated and complications such as toxic megacolon, mesenteric edema, and bowel perforation can develop.
Delay in diagnosis is significantly associated with higher mortality rate from PMC. The gold standard for diagnosis of PMC is C. difficile cytotoxin assay, though enzyme immunoassay for toxin A and B as well as PCR have a more rapid turnaround time.
Ultrasound can provide the first signs of C. difficile pseudomembranous colitis. Sonographic signs include pancolitis (typically concentric nodular thickening ranging between 5 to 20 mm thickness), mural irregularity, pericolonic increased echogenicity due to mesenteric edema, and simple ascites. Lack of hyperemia on color Doppler sonography may be helpful.
Treatment begins with stopping concurrent antibiotic therapy if possible, and initiating metronidazole or vancomycin to treat the PMC.