Fig. 5

A colonic resection specimen from a patient with COVID-19 and no gastrointestinal symptoms shows subtle features of viral infection. The colonic crypts are slightly dilated near the surface and have a slightly tufted appearance (asterisk) that reflects clustered epithelial cells with nuclear crowding (A). The same areas show strong signal for spike protein RNA by in situ hybridization (asterisk) using a brown chromagen (B). Another patient with mild respiratory symptoms due to COVID-19 developed gastrointestinal bleeding. Biopsy samples from the duodenal mucosa shows normal villous architecture with patchy hemorrhages (asterisk) and regenerative epithelium with cytoplasmic depletion. C Platelet-rich thrombi (asterisk) are present in vessels (D). A third patient with COVID-19 developed severe diarrheal symptoms presumably due to the pro-inflammatory state promoted by the virus. Samples obtained from the jejunum display mild villous shortening with striking crypt hyperplasia and regenerative epithelial changes unaccompanied by substantially increased inflammation (E). Colonic samples from the same patient show a similar degree of epithelial cell injury without increased inflammation. Dilated crypts (asterisk) contain mucin-depleted cells with eosinophilic cytoplasm and disorganized nuclei (F)