Specialist's Corner
COVID-19 may also trouble digestive organs
The new virus SARS-CoV-2 (COVID-19) mainly attacks lining of the airways in the cells thus affecting the respiratory tract, with a spectrum of symptoms, from mild infections as fever and cough, to pneumonia and acute respiratory distress syndrome in the most severe cases. However, what is unnerving about the infection is that, its effects are not limited to the respiratory system only. Other organs such as the gastrointestinal (GI) tract and liver seem to be targeted by the virus as well. According to a report, the disease severity can cause haematological changes and even worsen the condition of patients with digestive system diseases. A variety of imaging scans performed on hospitalized COVID-19 patients showed bowel abnormalities, according to a study published online May 11 in Radiology. Many of the effects were severe and linked with clots and impairment of blood flow.
The study’s lead author Dr Rajesh Bhayana, who works in the department of radiology at Massachusetts General Hospital in Boston said some findings were typical of bowel ischemia, or dying bowel, and in those who had surgery we saw small vessel clots beside areas of dead bowel. Patients in the ICU can have bowel ischemia for other reasons, but we know COVID-19 can lead to clotting and small vessel injury, so bowel might also be affected by this. And, these findings are not really surprising. Our emerging understanding of COVID-19 has found the disease to have multisystem involvement including the nervous, cardiac, vascular (excess clotting) and finally the digestive systems, among others. It seems that this disease is intricate, in the sense that it can involve multiorgan systems, rather than being a disease of the respiratory system solely. In fact, a study published online May 13 in the journal Science Immunology has found evidence that SARS-CoV-2, the virus behind COVID-19, can infect the human digestive system. Researchers led by Siyuan Ding of Washington University School of Medicine in St. Louis, said their findings “highlight the intestine as a potential site of SARS-CoV-2 replication, which may contribute to local and systemic illness and overall disease progression”. That seems to be borne out by the Boston study. That research included 412 COVID-19 patients who were hospitalized between March 27 and April 10. They averaged 57 years of age, and 134 of them underwent abdominal imaging, including 137 radiographs, 44 ultrasounds, 42 CT scans, and one MRI. In about 50% of COVID-19 cases, the presence of SARS-CoV-2 in faecal samples and detection of SARS-CoV-2 in intestinal mucosa of infected patients suggest that enteric symptoms could be caused by invasion of ACE2 expressing enterocytes and the GI tract may be an alternative route of infection. In over half of the patients, faecal samples remained positive for SARS-CoV2 RNA for a mean of 11 days after clearance of respiratory tract samples. A recent study further confirmed that 8 of 10 infected children had persistently positive viral rectal swabs after nasopharyngeal testing was negative. Importantly, live SARS-CoV-2 was detected on electron microscopy in stool samples from two patients who did not have diarrhoea, highlighting the potential of faecal-oral transmission.
According to a study from Wuhan, 16 percent of patients presented with gastrointestinal symptoms reported:
- Loss of appetite is the most common symptom. Nausea and vomiting, Diarrhoea, abdominal pain are the other GI symptoms.
- Fecal samples remained positive for SARS-CoV-2RNA for nearly 28 days from the first symptom whereas respiratory samples were positive up to 17 days from the first symptom. It means a patient can continue to shed the Virus RNA in stools in spite of getting cured from respiratory ailments. So, the role of the feco-oral route of acquiring the infection cannot be neglected and one needs to follow hygienic practices after using toilets.
- Liver dysfunction is seen in patients with severe COVID-19 disease. An abnormality in liver function blood test is generally found in COVID-19 symptomatic patients. One of the components in liver function tests called ALT is elevated in them. ALT elevation was found in 16 to 53% of patients. However, one need not panic as no cases of acute liver failure have been reported so far.
The above observations highlight the gastrointestinal and liver involvement in COVID-19 patients; however, the final outcome or recovery depends primarily on the management of lung issues. Development of GI symptoms does not indicate the severity of COVID-19 disease.
When liver cells are inflamed or damaged, they can leak higher than normal amounts of enzymes into the bloodstream. Elevated liver enzymes aren’t always a sign of a serious problem, but this laboratory finding was seen in people with SARS or MERS. In one study of hospitalized COVID-19 patients in Wuhan, 27 percent had kidney failure. One recent report found signs of liver damage in a person with COVID-19. Doctors said it was not clear, though, if the virus or the drugs being used to treat the person caused the damage. During the SARS outbreak, scientists even found the virus that causes this illness in the tubules of the kidneys. There’s “little evidence,” though, to show that the virus directly caused the kidney injury, according to a World Health Organization report. What actually happens is: When you have pneumonia, you have less oxygen circulating and that can damage the kidneys. With any infection, the body’s immune system responds by attacking the foreign virus or bacteria. While this immune response can rid the body of the infection, it can also sometimes cause collateral damage in the body. This can come in the form of an intense inflammatory response, sometimes called a “cytokine storm.” The immune cells produce cytokines to fight infection, but if too many are released, it can cause problems in the body. A lot of the damage in the body during COVID-19 is due to what we would call a sepsis syndrome, which is due to complex immune reactions. The infection itself can generate an intense inflammatory response in the body that can affect the function of multiple organ systems.
These studies provide new insights into our understanding of the prevalence, aetiology and potential mechanisms of COVID-19 in the GI tract crucial for defining prevention measures, clinical care and treatment strategies. Unanswered questions and challenges remain, such as the significance of virus detection in the stool/rectal swabs of asymptomatic subjects, whether ACE2 is a direct mediator for SARS-CoV-2 entry into the GI tract and how the virus could survive passage through extreme pH environment of the digestive system. Currently, prolonged fecal shedding in infected patients even after viral clearance in respiratory tract suggests that stool testing should be considered in patients with COVID-19 with appropriate transmission precautions for hospitalised patients who remain stool positive. Further research to determine the viability and infectivity of SARS-CoV-2 in faeces is required to control the spread of the virus especially in asymptomatic carriers.
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