In this Special Feature, we round up the existing evidence on the gastrointestinal symptoms in COVID- 19.
But according to a recent review, 53% of people hospitalized with COVID- 19 experience at least one gastrointestinal (GI) symptom at any time during their illness.
And there’s increasing evidence that encountering GI symptoms with COVID- 19, or developing COVID- 19 alongside underlying GI conditions, may increase the risk of disease severity and negative complications.
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In this Special Feature, Medical News Today review what we know so far about the relationship, prevalence, and impact of GI symptoms on COVID- 19 infections.
GI symptoms associated with COVID- 19
Respiratory symptoms, such as coughing or trouble breathing, are the most common symptoms of COVID- 19.
But early reports out of China made it clear that COVID- 19 can also trigger GI system symptoms. The GI system includes:
- the mouth
oesophagus, the tube that connects to the stomach
small and large intestines
- the anus
The first person with confirmed COVID- 19 in the United States also experienced 2 days of nausea and vomiting before developing diarrhoea. And one of the earliest American studies found that around 32% of patients with the disease experienced diarrhoea, nausea, or loss of appetite.
The research is ever-evolving. But according to a review published this month analyzing 125 articles and a total of 25, 252 patients, the most common GI symptoms associated with COVID- 19 include:
- lack of appetite (19. 9%)
- lack of smell or taste (15. 4%)
- diarrhoea (13. 2%)
- nausea (10. 3%)
- vomiting up blood or GI bleeding (9. 1%)
Another review published in late January found much broader ranges of symptom prevalence rates, such as:
. diarrhoea (9– 34%)
. nausea, vomiting, or both (7– 16%)
. abdominal pain (3– 11%)
Less commonly, COVID- 19 may also cause:
- acid reflux
- colitis, or intestinal inflammation
- GI bleeding
The disease may also destroy bowel tissues and reduce intestinal movement.
Right now, it seems most people who experience GI symptoms with COVID- 19 develop them alongside respiratory symptoms.
However, a review from late 2020 found around 20% of people with COVID- 19 infections only experience GI symptoms. And sometimes, these symptoms develop before respiratory symptoms or fever develops.
Early studies suggest GI symptoms tend to occur during the early stages of the infection. But more research is needed to confirm when GI symptoms develop in COVID- 19 cases if there is a specific time frame.
How COVID- 19 causes GI symptoms
Researchers are still learning more about how infection with SARS- CoV- 2 affects different parts of the body.
There is evidence that SARS- CoV- 2 can infect cells in the respiratory and GI tract, as well as cells in other locations in the body.
Most studies show the SARS- CoV- 2 virus enters intestinal cells, or enterocytes, and respiratory cells using the angiotensin-converting enzyme 2 (ACE- 2) protein as a receptor. The ACE- 2 receptors are embedded in cellular membranes. It helps regulate blood pressure by controlling levels of the protein angiotensin, which encourages blood vessels to constrict and raise blood pressure.
The virus enters intestinal cells after its characteristic spike proteins bind to ACE- 2. Once inside the cell, the virus uses the cells’ machinery to produce copies of viral proteins and ribonucleic acid (RNA). RNA is the genetic material of retroviruses, such as SARS- CoV- 2, much like human DNA.
When SARS- CoV- 2 particles leave an infected cell, it triggers the release of cytokines, small proteins that play a role in inflammation. This process may cause GI symptoms.
GI symptoms can also occur as viruses destroy or damage GI tissues, especially pain, nausea, and diarrhoea. Some research shows that COVID- 19 may also change the gut microbiota, the community of microbes that normally inhabit the intestines or stomach.
Once in the GI tract, the virus can also travel through the portal vein, the vein that drains blood from the digestive tract. This can allow viruses to impact the vagus nerve, causing a nauseous sensation.
Nausea and diarrhoea are also common symptoms of medications that healthcare professionals often use to manage COVID- 19, such as antivirals and antibiotics.
There is increasing evidence that SARS- CoV- 2 could pass on to others via faecal-oral transmission. This means people could acquire an infection by accidentally consuming or inhaling droplets of infected faeces.
Faecal samples from the first person with confirmed COVID- 19 in the U. S. contained virus particles. Other coronaviruses can also cause viral shedding, referring to the release of viral particles in faeces.
Some research even suggests people may shed viral particles in their faeces after the virus is undetectable in the upper respiratory system, such as the lungs, nose, or throat.
If true, this could change how someone can spread the virus to others and for how long. But researchers have yet to determine whether the proteins and particles shed in faeces are infectious, or capable of actually causing disease.