[Endoscopic findings in microscopic colitis: a diagnostic challenge in clinical practice]

Microscopic colitis (MC) is a chronic inflammatory bowel disease characterized by watery diarrhea and a macroscopically normal-appearing colonic mucosa on colonoscopy. It is classified into lymphocytic colitis (LC) and collagenous colitis (CC). Its incidence has increased in developed countries, but data from Latin America remain limited. We present the case of a 65-year-old woman with fibromyalgia and recent use of duloxetine, who presented with chronic diarrhea. Colonoscopy revealed edematous mucosa with loss of vascular transparency, deep furrows with a cobblestone-like appearance, and an open dot-like surface pattern. Histopathological analysis confirmed a diagnosis of LC. After discontinuing duloxetine, the diarrhea resolved spontaneously without the need for corticosteroids. Although MC has traditionally been described as presenting with a normal-appearing colonic mucosa, studies have reported subtle and nonspecific findings such as edema, erythema, and vascular pattern abnormalities. Detection of these findings can be improved through the use of virtual chromoendoscopy and high-definition equipment. Recognizing these patterns may enhance biopsy targeting and increase the detection of this condition, especially in the evaluation of chronic diarrhea. However, endoscopic findings must be differentiated from other conditions, such as inflammatory bowel disease or ischemic colitis.