Chronic Diarrhea Owing to Underlying Microscopic Colitis

The goal of this observational study is to search for accurate diagnoses for patients with chronic diarrhea and assess the prevalence of microscopic colitis. The main question\[s\] it aims to answer \[is/are\]: Does microscopic colitis account for a significant portion of patients with chronic diarrhea? Participants will subjected to: * Routine laboratory examination. * Colonoscopy: A total colonoscopy will be done with visualization of the terminal ileum. Biopsies will be taken from each segment of the colon and any abnormal appearing areas, the right-sided colon (cecum, ascending colon, and transverse colon), the left-sided colon (descending colon and sigmoid colon), and the rectum.