Background. Subacute and chronic long-term effects of coronavirus disease 2019 (COVID-19) in different organ systems have been studied in post-COVID patients recently. COVID-19 may cause gastrointestinal (GI) system findings due to the presence of its receptor, angiotensin converting enzyme type 2 (ACE2), which is extensively expressed in the GI tract. In this study, we aimed to evaluate the post-infectious histopathological alterations of COVID-19 in pediatric patients who had GI symptoms.

Methods. Fifty-six specimens of upper endoscopic biopsies (including esophagus, stomach, bulbus and duodenum) obtained from seven patients and 12 specimens of lower endoscopic biopsies obtained from one patient who had GI symptoms after having COVID-19 (proven by polymerase chain reaction [PCR]) were evaluated as the study group. Forty specimens from five patients presenting with similar complaints but without COVID-19 were selected as the control group. All biopsy materials were immunohistochemically stained with the anti-SARS-CoV-2S1 antibody.

Results. In all biopsies of the study group, anti-SARS-CoV-2S1 antibody was detected with moderate cytoplasmic positivity in epithelial cells and inflammatory cells in the lamina propria. No staining was observed in the control group. Epithelial damage, thrombus, or no other specific findings were detected in the GI tract biopsies of any of the patients.

Conclusions. The virus antigen was detected immunohistochemically in the stomach and duodenum, but not in the esophagus, even months after infection and causes gastritis and duodenitis. No specific histopathological finding was observed from non-COVID-19 gastritis/duodenitis. Therefore, the post-COVID-19 GI system involvement should be kept in mind in patients presenting with dyspeptic symptoms even if several months have passed.

Keywords: COVID-19, biopsy, child, endoscopy, gastrointestinal, immunohistochemistry