Microscopic colitis (lymphocytic and collagenous), eosinophilic colitis, and celiac disease.

Multiple tests are needed to diagnose a patient with noninfectious diarrhea. Some patients will be mistakenly labeled as diarrhea-predominant irritable bowel syndrome (IBS-D) because of nonspecific computed tomographic scans and grossly normal endoscopic findings. It is crucial to understand other less common pathologies to avoid these instances of misdiagnosis. This article focuses on microscopic colitis (MC), eosinophilic colitis (EC), and celiac disease. MC is an inflammatory condition of the colon that presents with two subtypes, only to be differentiated by histology. EC is a rare chronic inflammatory process. Depending on the extent of the disease, it can present with mild diarrhea, malabsorption, or at its worst, cause obstruction and perforation. Celiac disease affects the small bowel, but interestingly can present similarly to colitis. Both MC and EC respond to oral budesonide. Patients with celiac disease improve on gluten-free diets. These treatments are distinctly different from typical IBS-D care plans.