key: cord-0905955-bwardgsu authors: Dioscoridi, Lorenzo; Giannetti, Aurora; Bonato, Giulia; Vantaggiato, Giuseppe; Vicari, Francesco; Airoldi, Aldo title: COVID-19 and Diarrhoea: the Therapeutic Role OF LMWH date: 2021-02-20 journal: SN Compr Clin Med DOI: 10.1007/s42399-021-00825-3 sha: 9ad6e1b2d7c1dfdb0e09ebb5b45fa3c6e45cfb78 doc_id: 905955 cord_uid: bwardgsu nan We read with great interest the paper by Ghimire S et al. [1] demonstrating that diarrhoea in COVID-19 is related to a worse prognosis. Furthermore, the authors confirmed that it is the most common gastrointestinal symptom related to SARS-COV-2 infection. How to treat diarrhoea is not still clear; however, the therapeutic role of low molecular weight heparin (LMWH) should be underlined because it is based on pathophysiological principles. On one hand, an association between diarrhoea in COVID-19 and increased level of serotonin (5-HT) has been recently demonstrated [2] , and it is widely known that 5-HT stimulates platelet aggregation [3] and consequently increases the risk of micro and macro-thrombosis, worsening the prognosis of the disease. On the other hand, diarrhoea in COVID-19 seems to be related to both direct and indirect mucosal damage: the direct damage may be due to the disruption of the tightjunctions by SARS-COV-2 itself [4] , and the indirect effect can be caused by the systemic inflammatory response and the ischemic damage of enterocytes [4] . This mucosal damage may increase the bacterial translocation through the intestinal wall. That contributes to the persistence of diarrhoea and can cause a bacterial systemic superinfection: IL-6, a fundamental pathogenetic cytokine for COVID-19 severity but also a biomarker of inflammation associated with endotoxemia and sepsis [5] , achieved high levels in patients with diarrhoea [2] . Furthermore, the associated damage of enterochromaffin cells and intrinsic enteric neurons can increase the release of circulating 5-HT, establishing a vicious circle [3] . LMWH acts on these pathogenetic mechanisms. On one side, it decreases systemic and local platelet aggregation interfering with the hypercoagulable state induced by 5-HT [3] ; on the other side, it improves intestinal microcirculation able to decrease enterocytic damage and therefore bacterial translocation [5] . For these reasons, LMWH represents the proper therapy for diarrhoea in COVID-19 patients and, so on, contributes to improve the prognosis. Authors' Contributions LD and AD wrote the paper; GB and GV performed the literature research; FV and AA revised the manuscript. All the authors approved the final version. Code Availability n/a Declarations Ethics Approval This article does not contain any study with human participants or animals performed by any of the authors. Diarrhoea is associated with increased severity of disease in COVID-19: systemic review and metaanalysis Serotonin is elevated in COVID-19-associated diarrhoea This article is part of the Topical Collection on COVID-19 The role of serotonin in thrombogenesis Gastrointestinal symptoms of 95 cases with SARS-CoV-2 infection Enoxaparin prevents portal vein thrombosis and liver decompensation in patients with advanced cirrhosis Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. SN Compr Conflict of Interest The authors declare no competing interests.