Covid‐19 and the digestive system

Original Article: Wong SH, Lui RN, Sung JJ. Covid-19 and the digestive system. J Gastroenterol Hepatol. 2020;35(5):744-748.

Author of summary: Marianna Coppola ; Reviewer: Giulia Peserico

Original Article Published on March 24th, 2020

The current pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) typically present with fever and respiratory illness, but some patients also report gastrointestinal symptoms such as diarrhea, vomiting, and abdominal pain. In this article, we analyze the main gastrointestinal aspects of the disease.

Studies have identified the SARS‐CoV‐2 RNA in rectal swabs and stool specimens of Covid‐19 patients, even after the clearance of the virus in the upper respiratory tract, and electron microscopy on biopsy and autopsy specimens showed active viral replication in both small and large intestines; this evidences may explain the frequent occurrence of diarrhea in coronavirus infection. Moreover, its viral receptor (Angiotensin Converting Enzyme 2) is highly expressed in gastrointestinal epithelial cells and staining of viral nucleocapsid protein was visualized in cytoplasm of gastric, duodenal and rectal epithelium, suggesting the receptor‐mediated entry into the host cells and provided basis for its possible transmission route through the fecal contents. These events suggest that SARS‐CoV‐2 can actively infect and replicate in the gastrointestinal tract.

The first case reporting gastrointestinal symptoms is a 35yo man in the United States that presented with a 2‐day history of nausea and vomiting upon hospital admission, followed by diarrhea and abdominal discomfort on the second day of hospitalization; furthermore, during the early epidemic, in a familial cluster diarrhea was manifested in two young adults (aged 36 and 37 years) out of the six patients, up to 8 times a day.

A large study with 1,099 patients from 552 hospitals in China reported nausea or vomiting in 55 (5.0%) and diarrhea in 42 (3.8%) patients. Several other cohorts have reported frequencies of these symptoms with variable rates (the most frequent is diarrhea in 2-10% of patients, followed by nausea in 1-10% of cases) and they are observed also in pediatric patients. However, gastrointestinal symptoms in Covid-19 are less common than in SARS and MERS infection.

In 14.8–53.1% patients with Covid‐19 has been observed liver injury manifested by with abnormal levels of ALT (alanine aminotransferase) and AST (aspartate aminotransferase) during the course of disease, with mostly mild elevation in serum bilirubin; in another study of 56 patients, GGT (gamma‐glutamyl transferase) dosage was high in 54% of cases. The mechanism of liver injury has to be investigated more but the causes might be a direct viral infection of hepatocytes, an immune‐related injury or drug hepatotoxicity. There is also suggestion that the virus may bind to cholangiocytes through the ACE2 receptor to dysregulate the liver function; an histological examination of the liver biopsy from a deceased Covid‐19 patient showed microvesicular steatosis and mild lobular activity but no viral inclusion was observed in the liver.

Several studies have demonstrated the presence of viral RNA in stool or anal/rectal swabs of Covid‐19 patients. In a study that evaluated 73 Covid‐19 patients, 39 (53.4%) were tested positive for SARS‐CoV‐2 RNA in stool, with a duration of positive stool ranging for 1-12 days, and 17 (23.3%) patients remained positive with stool viral RNA after showing negative in their respiratory samples. A previous study of SARS‐CoV indicated that viral RNA could still be detected after 30 days in stool of SARS patients but the viral dynamic of SARS‐CoV‐2 in the gastrointestinal tract may not follow that of SARS‐CoV as observed in the respiratory tract.

The tropism of SARS‐CoV‐2 to the gastrointestinal tract and its positive detection in stool highlight the importance of patient care and infection control, especially if gastrointestinal symptoms occur before the onset of pyrexia and respiratory symptoms. The gastrointestinal involvement of Covid‐19 point out the importance to consider several clinical policies and the need of personal protective equipment in the endoscopy setting.

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