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 non-respiratory 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 socio-sanitary 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.