Considerations and perspectives on digestive diseases during the COVID-19 pandemic: a narrative review

Coronavirus disease 2019 (COVID-19) was initially reported in December 2019, and since then it has become a pandemic with newly confirmed cases and deaths increasing continuously. The COVID-19 pandemic has dramatically impacted the organization and execution of activities in the clinical sector. Asymptomatic infections are increasingly being identified when patients seek medical advice for nonrespiratory system illnesses, particularly digestive system symptoms. This has posed a significant challenge for clinical diagnosis and treatment. Based on the clinical symptoms of patients with COVID-19 reported to date, patients with typical clinical symptoms of COVID-19 may also present with symptoms associated with the digestive system. Digestive illness symptoms in patients with COVID-19 are underscored by a bidirectional relationship between respiratory and digestive systems. Because the clinical diagnosis and treatment of digestive illnesses caused by COVID-19 have been challenging so far, we hypothesized that investigating the pathogenesis of digestive system diseases in patients with COVID-19 will provide potential novel targets for its prevention and treatment, and concurrently reduce COVID-19 virulence and sociosanitary burden. This review summarizes the relationship between the digestive and respiratory systems in patients with COVID-19 from the perspective of the "gut-lung" axis. We discuss extant literature on the pathogenesis of COVID-19-related digestive symptoms, which may facilitate differential diagnosis and treatment of this condition.