Microscopic colitis (MC) is an idiopathic inflammatory bowel disease characterized by watery, non-bloody diarrhea and histopathological changes but normal endoscopic findings. Increasing evidence now suggests that alterations in the gut microbiota contribute to the pathogenesis of MC. In this narrative review, we summarize evidence from nine case-control studies examining microbial composition using sequencing technology. The research presented here illustrates reduced alpha diversity, high dysbiosis, and pro-inflammatory oral-associated taxa enrichment, such as Veillonella dispar, and loss of protective microbes such as Akkermansia muciniphila and Bacteroides stercoris. These microbial changes have the potential to be non-invasive diagnostic biomarkers that can differentiate MC from other etiologies. In addition, the characterization of gut microbiota in MC can guide personalized therapeutic strategies, such as directed probiotic therapy or fecal microbiota transplantation, to help restore microbial balance. These microbial patterns can be applied to guide the creation of diagnostic biomarkers and personalized therapy. Despite differences in sample types and sequencing methods, general microbial trends highlight the need for further longitudinal and standardized investigations.

Introduction: Acute severe ulcerative colitis (ASUC) represents a life-threatening medical emergency. One-third of ASUC patients are steroid non-responders. Our study aimed to create a new ASUC algorithm to predict corticosteroid response in the early course of the disease. Materials and Methods: A cross-sectional study included 103 patients with ASUC (65 male, 38 female). We calculated the serum CRP to 25-hydroxy 25 OH vitamin D ratio at admission. Logistic regression determined patients’ response to glucocorticoids, depending on the CRP/25 OH vitamin D ratio value. Results and Discussion: Significant differences were observed in the CRP/25 OH vitamin D ratio at admission between glucocorticoid responders and non-responders (p = 0.001). A negative correlation was found between glucocorticoid response and CRP/25 OH vitamin D levels (Spearman’s rho = −0.338, p < 0.01). Logistic regression revealed a significant association (p = 0.003) with a model chi-square value of 11.131 (p = 0.001). ROC curve analysis showed an AUC of 0.696 (p = 0.001), indicating moderate discriminatory ability. To achieve 91% sensitivity, the CRP/25 OH vitamin D ratio must be less than 3.985 to predict a complete glucocorticoid response. Conclusions: The serum CRP to 25 OH vitamin D ratio on the first day of hospital admission can potentially determine the response to glucocorticoids in patients with ASUC and significantly affect the mortality of these patients.