The COVID-19 pandemic prompted questions about how the SARS-CoV-2 virus affects various body parts, including the liver. This article provides clear information regarding COVID-19’s influence on liver health.
COVID-19’s Impact on the Liver
Liver involvement is a recognized aspect of COVID-19, with studies consistently showing that the virus can affect liver function. Many patients infected with SARS-CoV-2 exhibit some degree of liver abnormality, often indicated by elevated levels of liver enzymes, such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST). These enzymes are released into the bloodstream when liver cells are damaged.
Observations from various studies indicate that elevated liver enzymes occur in a notable percentage of COVID-19 patients. The reported prevalence of liver injury, characterized by these enzyme elevations, varies from approximately 14% to 76% across different patient cohorts. The severity of liver injury also tends to correlate with the overall severity of the COVID-19 illness, with more pronounced changes seen in those with severe disease.
Mechanisms of Liver Injury
COVID-19 can affect the liver through several mechanisms.
Direct Viral Infection
The SARS-CoV-2 virus can directly infect liver cells. It uses the angiotensin-converting enzyme 2 (ACE2) receptor to enter human cells, and these receptors are present on various liver cells, including hepatocytes (main liver cells) and cholangiocytes (bile duct cells). This direct viral entry can lead to damage within the liver tissue.
Immune Response
The body’s immune response to the infection can also harm the liver. In some individuals, COVID-19 triggers an overactive immune response, sometimes referred to as a “cytokine storm.” This widespread inflammatory reaction releases signaling molecules that can cause systemic inflammation and damage to multiple organs, including the liver.
Drug-Induced Liver Injury (DILI)
Medications used to treat COVID-19 can also contribute to liver stress or injury, a phenomenon known as drug-induced liver injury (DILI). Various antiviral drugs, such as remdesivir and lopinavir/ritonavir, as well as certain anti-inflammatory agents and even common antipyretics, have been associated with potential liver side effects. The incidence of DILI in COVID-19 patients has been reported to be as high as 25.4%.
Hypoxia
Another contributing factor is hypoxia, or reduced oxygen supply, to the liver. Patients with severe COVID-19, particularly those experiencing significant respiratory distress, can have lower oxygen levels in their blood. This lack of adequate oxygen can lead to hypoxic liver injury, causing damage to liver cells.
Identifying Liver Distress
Recognizing signs of liver involvement during or after a COVID-19 infection is important for timely medical evaluation. Common symptoms that might suggest liver distress include fatigue, nausea, and a reduced appetite. Some individuals may also experience discomfort or pain in the upper right abdomen.
Less common but more severe indicators of liver issues can include jaundice (which is a yellowing of the skin or eyes), along with dark-colored urine and light-colored stools. These symptoms indicate problems with bilirubin processing or bile flow. If any of these signs appear, medical attention should be sought promptly.
Laboratory tests are key in identifying liver distress. Blood tests often reveal elevated levels of liver enzymes like ALT and AST, indicating liver cell damage. Elevations in alkaline phosphatase (ALP) and bilirubin levels can also be observed, suggesting issues with bile ducts or overall liver function. In some cases, AST levels may be higher than ALT, which can sometimes point to multi-organ involvement rather than solely liver-specific injury.
Who is Most Affected
Certain factors can increase an individual’s susceptibility to liver damage from COVID-19.
Pre-existing Liver Conditions
Individuals with pre-existing liver conditions are generally at higher risk for more pronounced liver injury and worse outcomes. This includes those with chronic liver diseases such as non-alcoholic fatty liver disease, hepatitis B or C, and cirrhosis. For instance, patients with cirrhosis have been shown to have a significantly higher mortality rate if they contract COVID-19.
Other Health Conditions (Comorbidities)
Other underlying health conditions, known as comorbidities, also play a role in increasing vulnerability. Conditions like diabetes, obesity, and hypertension are associated with a greater likelihood of experiencing liver complications during COVID-19. These conditions often involve systemic inflammation that can exacerbate the effects of the virus on the liver.
Severity of COVID-19 Infection
The severity of the COVID-19 infection itself is another factor. Patients who experience severe forms of the disease, particularly those requiring intensive care unit (ICU) admission or mechanical ventilation, are more prone to developing liver complications. This heightened risk is often due to the systemic nature of severe illness, including widespread inflammation and reduced oxygen delivery to organs.
Post-COVID Liver Health
For most individuals who experience elevated liver enzymes during acute COVID-19, these abnormalities tend to resolve on their own as the patient recovers from the infection. The liver has a remarkable capacity for regeneration, and often, the transient inflammation and stress caused by the infection do not lead to lasting damage. This recovery typically occurs without the need for specific liver-focused treatments.
However, some individuals may experience persistent issues as part of “Long COVID,” where symptoms linger for weeks or months after the initial infection. In these cases, there can occasionally be prolonged liver enzyme abnormalities or even indicators of increased liver stiffness or fibrosis. This potential for ongoing inflammation or early scarring highlights the importance of continued monitoring.
For individuals with pre-existing liver conditions or those who experienced significant liver involvement during the acute phase of COVID-19, follow-up with a healthcare provider is important. This allows for monitoring of liver function tests and assessment for any lingering effects. Regular medical evaluation helps ensure that liver health returns to baseline or that any persistent issues are identified and managed appropriately.