Need to treat?

A 76-year-old patient presented with a two-week history of watery diarrhoea. There was no history of fever, abdominal pain nor bloody stools. Blood analysis showed inflammation (C-reactive protein of 160 mg/L, reference <5 mg/L) and a normal complete blood count. Faecal culture showed no pathogens. The patient was treated with a three-day course of azithromycin 500 mg daily without improvement. Subsequently, a colonoscopy was performed, which showed no macroscopical abnorma-lities. Randomly taken biopsies revealed a thin blue fringe on the colonic epithelium (Figure 1).