Epidemiology
In most cases, a patient presenting with pseudomembranous colitis has recently been on antibiotics. Antibiotics disturb the normal bowel bacterial flora. Certain antibiotics such as ampicillin have a higher propensity to create an environment where pseudomembranous colitis can outcompete the normal gut flora. Clindamycin is the antibiotic classically associated with this disorder, but any antibiotic can cause the condition. Even though they are not particularly likely to cause pseudomembranous colitis, cephalosporin antibiotics (such as cefazolin and cephalexin) account for a large percentage of cases due to their very frequent use. Diabetics and the elderly are also at increased risk, although half of cases are not associated with risk factors.
Other risk factors include increasing age and recent major surgery. There is some evidence that proton pump inhibitors are a risk factor for C. difficile infection and pseudomembranous colitis, but others question whether this is a false association or statistical artifact (increased PPI use is itself a marker of increased age and co-morbid illness). indeed, one large case-control study showed that PPIs are not a risk factor.
Read more about this topic: Pseudomembranous Colitis