When investigating the prevalence of conditions following COVID-19, researchers have found the vast majority of people reporting at least one persistent short-term symptom and more than half indicating long-term symptoms. These short- and long-term symptoms typically include tiredness, overall pain and discomfort, poor sleep, breathlessness, and anxiety or depression.

There is now evidence that the gastrointestinal (GI) system may also be affected by SARS-CoV-2, the coronavirus that causes COVID-19. It is believed that because ACE2 (angiotensin-converting enzyme 2) receptor activity is highly expressed in the GI tract, the receptors help the virus gain entry into GI organs. Research has also shown SARS-CoV-2 making its way into the colon and feces of COVID-19 patients.

The Gastrointestinal System

The GI system is one of the body’s 11 organ systems that mainly serves the life-sustaining role of digesting solid foods and liquids into smaller, absorbable molecules that can be used for cellular fuel, growth, and repair. The system can be broken down into the following components:

1. Mouth
2. Pharynx (throat)
3. Esophagus
4. Stomach
5. Small intestine
6. Large intestine
7. Rectum
8. Anus

Along the journey, food and liquids are acted upon by digestive juices and enzymes made by accessory organs—the salivary glands, liver, gallbladder, and pancreas, which enable their absorption.

COVID-19 and the Gastrointestinal System

In a comprehensive study review published by Harvard University, three areas of impact of COVID-19 on the GI system were identified: COVID-19 GI symptoms, GI complications, and long-term GI effects.

COVID-19 Gastrointestinal Symptoms

While COVID-19 mainly causes fever, dry cough, and shortness of breath, it can affect multiple areas of the body. Nausea, vomiting, and diarrhea can occur in the GI tract, either by themselves or alongside other COVID-19 symptoms.

GI symptoms occur in as many as a third of all COVID-19 patients. An analysis of 60 studies consisting of 4,243 COVID-19 patients found that overall prevalence of GI symptoms was 17.6%; 11.8% of patients with mild disease and 17.1% of patients with severe disease had GI symptoms.

In another review of 43 studies consisting of 18,246 COVID-19 patients, 11.5% of patients had diarrhea (the most common symptom), 6.3% of patients experienced nausea and vomiting, and 2.3% suffered abdominal pain. Disease severity was similar to the study above, with 17.5% experiencing severe illness and 9.8% mild illness.

COVID-19 Gastrointestinal Complications

There is a high risk of GI complications in people with severe COVID-19, such as:

• Elevated liver transaminases (enzymes involved in filtering toxins from the body), which can cause acute liver injury and occur in close to two-thirds of severe COVID-19 cases.
• Acute cholecystitis, or inflammation of the gallbladder, which is common in people with severe COVID-19 and is usually due to the gallbladder having trouble emptying (for reasons still unknown).
• Acute pancreatitis, also common in severe COVID-19 patients for reasons still unknown.
• Ileus, or a loss of normal intestinal contraction and subsequent food build-up, and feeding intolerance, which have been observed in roughly half of critically ill COVID-19 patients in intensive care.
• A distinct colonic syndrome, reported in severely ill COVID-19 patients and involving severe gaseous distention in the colon with no obvious obstruction.
• Mesenteric ischemia, the most serious complication, involving inadequate blood supply to the small intestine, observed in about 4% of critically ill COVID-19 patients with a mortality rate of up to 40%.

COVID-19 Long-Term Gastrointestinal Effects

A study in China investigated the gastrointestinal symptoms of 117 COVID-19 patients discharged from the hospital that were not present a month prior to the illness. After 90 days, 44% (52 of 117 patients) reported GI symptoms.

• Loss of appetite (the most common symptom) – 24% (28 patients)
• Nausea – 18% (21 patients)
• Acid reflux – 18% (21 patients)
• Diarrhea – 15% (17 patients)
• Abdominal distention – 14% (16 patients)
• Belching – 10% (12 patients)
• Vomiting – 9% (11 patients)
• Abdominal pain – 7% (eight patients)
• Bloody stools – 2% (two patients)

While the remaining 65 patients did not have GI symptoms upon hospital admission or during hospitalization, 15 of the 52 patients (29%) experienced GI symptoms both upon admission and during their hospital stay, 34 patients (65%) had GI symptoms during hospitalization, and three patients (6%) had GI symptoms only after hospitalization.

‘Unusual Gastrointestinal Symptoms’ That Can Be Long-Term

The author noted that despite a lack of adequate data on the long-term GI effects of COVID-19, a general overview of the long-haul GI impacts was able to be conducted. COVID-19 was shown to produce “unusual gastrointestinal symptoms,” such as appetite loss, nausea, and acid reflux, that persisted for three months after hospitalization. Moreover, serious GI complications can result from severe COVID-19.

The author concluded that research on the frequency, severity, and treatment of these symptoms is needed, as well as further study into other long-term GI impacts and complications from COVID-19.

*Wun, T.T.R. (2022). COVID Long-Haulers: Gastrointestinal System. Harvard University – The Coronavirus Visualization Team. https://scholar.harvard.edu/cvt/covid-long-haulers-gastrointestinal-system%C2%A0