Involvement of digestive system in Covid-19: manifestations, pathology, management and challenges

The pandemic of novel coronavirus disease (COVID-19) has developed as a tremendous threat to global health. Although, most COVID-19 patients present with respiratory symptoms, some of them would present GI symptoms like diarrhoea, loss of appetite, nausea/vomiting and abdominal pain as the major complaints. These features may be attributable to the following fact: 1) COVID-19 is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its receptor angiotensin converting enzyme 2 (ACE2) was found to be highly expressed in gastrointestinal (GI) epithelial cells, providing a prerequisite for SARS-CoV-2 infection; 2) SARS-CoV-2 viral RNA has been found in the stool specimens of infected patients and 20% of patients showed prolonged presence of SARS-CoV-2 RNA in faecal samples after the virus converting negative in respiratory system. These findings suggest SARS-CoV-2 may be able to actively infect and replicate in the gastrointestinal tract. Moreover, gastrointestinal infection could be the first manifestation antedating respiratory symptoms and patients only suffering digestive symptoms but no respiratory symptoms as clinical manifestation was also reported. Thus, the implications of digestive symptoms in patients with COVID-19 is of great importance. In this review, we summarized the recent findings on epidemiology of GI tract involvement, potential mechanisms of faecal-oral transmission, GI and Liver manifestation, pathological/histological features in patients with COVID-19 and the diagnosis, management of patients with pre-existing GI and liver diseases as well as precautions for preventing SARS-CoV-2 infection during GI endoscopy procedure.