Objectives: To determine the extent of ulcerative colitis and associated factors in patients who underwent sigmoidoscopy at Liver Center, Jail Road, Lahore, Pakistan. Methods: In this retrospective cohort study, patients who underwent sigmoidoscopy from July 2013 to July 2020 at Liver Clinic, Jail Road, Lahore, were categorized into two cohorts: who had ulcerative colitis confirmed on histology and who had no ulcerative colitis. Extent and severity of the disease as well as coexisting pathologies were also noted. SPSS version 25 was used. Independent sample T-test was applied to compare quantitative variables like age and weight, and chi-square test to compare qualitative variables with two cohorts. The p-value less than 0.05 was opted as significant. Odd ratio with 95% confidence interval (CI) were also computed for each association. Results: About 11.55% patients (165 out of 1428) had ulcerative colitis, whose mean age and mean weight were 38.27 ± 14.15 years and 74.08 ± 13.20 Kg respectively. Among ulcerative colitis patients, 18.2% had proctitis, 22.4% had proctosigmoiditis, 27.7% had left-sided colitis, and 31.5% had extensive colitis. May endoscopic severity score was found 0,1,2, and 3 in 12.1%, 23.6%, 31.5%, and 32.7% patients respectively. Ulcerative colitis cohort had significant association with younger age (p<0.01), female gender (p<0.01), non or former smoking (p=0.02) and presentation with bloody diarrhea (p<0.01), and no association with body weight (p=0.311), presence of diabetes mellitus (p=0.311) and family history of IBD (P=0.368). Conclusion: Endoscopic extent and severity of ulcerative colitis is high in our studied population. Ulcerative colitis is more prevalent in younger age and female gender patients who presented with bloody diarrhea, while the presence of active smoking has negative association with finding the ulcerative colitis. However, presence of family history of IBD, diabetes mellitus and body weight of the patient has no statistical correlation with finding ulcerative colitis during sigmoidoscopic examination in our patients. doi: https://doi.org/10.12669/pjms.38.1.4648 How to cite this:Saleem A, Zeeshan M, Hazoor F, Mustafa G. Sigmoidoscopic extent of ulcerative colitis and associated factors in Pakistani population. Pak J Med Sci. 2022;38(1):---------. doi: https://doi.org/10.12669/pjms.38.1.4648 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.