Tehran University of Medical Sciences Journal of Biostatistics and Epidemiology 2383-4196 7 4 2021 12 15 321 343 Saber Soltani Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. AND Research Center for Clinical Virology, Tehran University of Medical Sciences, Tehran, Iran Armin Zakeri Department of Hematology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran. Iraj Pakzad Department of Microbiology, School of Allied Medical Sciences, Ilam University Medical Sciences, Ilam, Iran. Alireza Tabibzadeh Department of VirologyDepartment of Virology, Iran University of Medical Sciences, Tehran, Iran., Iran University of Medical Sciences, Tehran, Iran. Amir Mohammad Zakeri Pediatric Surgery Research Center, Research Institute for Children's Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Milad Zandi Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. AND Research Center for Clinical Virology, Tehran University of Medical Sciences, Tehran, Iran Sara Akhavan Rezayat Department of Health Care Management and Economics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. Mehrzad Jafarzadeh Endocrine research center, institute of Endocrinology and Metabolism, Iran University of Medical Science, Tehran, Iran. Parinaz Khalkhali Asl Department of Microbiology, School of Medicine, Golestan University of Medical Sciences, Golestan, Iran. Arghavan Zebardast Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Yousef Erfani Department of Medical Laboratory Sciences, School of Allied Medical Sciences, Tehran University Medical Sciences, Tehran, Iran. Ramin Shahbahrami Research Center for Clinical Virology, Tehran University of Medical Sciences, Tehran, Iran Reza Pakzad Department of Epidemiology, Faculty of Health, Ilam University Medical Sciences, Ilam, Iran. AND Health and Environment Research Center, Ilam University of Medical Sciences, Ilam, Iran. Pooneh Malekifar Department of Epidemiology, School of Public Health, Tehran University Medical Sciences, Tehran, Iran. 2021 05 08 2021 10 23 Introduction/aims: Since the start of a pandemic from Wuhan, China in 2019, there is tremendous attention in the COVID-19 manifestation. One of the most important COVID-19 clinical presentations is gastrointestinal symptoms. The current systematic review study aims to focus on the implication of the gastrointestinal tract in patients infected with SARS-CoV-2. Methods: For that we searched literature in MEDLINE, Scopus, Web of Science, and Embase. Also, the medRxiv was searched for preprints. The search was performed by using the following keywords "Covid-19", "Coronavirus", "SARS-CoV-2 infection", "SARS-CoV-2", "Gastrointestinal", "Gastrointestinal Tract", "digestive system". All the studies were conducted based on the PRISMA criteria. Results: Of 3028 retrieved documents, 111 studies with 21126 COVID-19 cases were included. The prevalence of any Gastrointestinal symptoms was 17.22% (14.48 to 20.13). The prevalence of diarrhea was 13.75% (12.07 to 15.44), anorexia 27.41% (21.53 to 33.29) and Nausea/vomiting 8.11% (6.87 to 9.35). Furthermore, the prevalence of other symptoms in our current study was fever 76.70% (73.42 to 79.83), cough 58.07% (54.59 to 61.52) and dyspnea/shortness of breath 24.63% (20.06 to 29.48). According to meta-regression results, age (p: 0.027) and fever (p<0.001) did have significant effect on prevalence of any Gastrointestinal symptoms. Conclusion: The anorexia, diarrhea, nausea, and vomiting are the most common Gastrointestinal presentations. The majorities of studies are in the Case series setting and conducted in China. https://jbe.tums.ac.ir/index.php/jbe/article/view/513