Cirrhosis is a severe condition marked by permanent scarring of the liver. Liver enzymes, such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST), are commonly used markers that indicate liver cell injury. While elevated enzyme levels typically signal liver problems, individuals with cirrhosis can have liver enzyme levels that appear normal. This can be misleading, as normal readings do not necessarily reflect the true extent of liver damage or disease severity.
What Liver Enzymes Indicate
Liver enzymes are proteins that play a role in various chemical reactions within the liver, including metabolism and detoxification. ALT and AST are two frequently measured enzymes in blood tests. ALT is found predominantly in the liver, making it a specific indicator of liver cell damage. AST is present in the liver but also in other organs like the heart, kidneys, and muscles.
When liver cells are injured or dying, they release these enzymes into the bloodstream, leading to elevated levels of ALT and AST detected in blood tests. Normal ranges for these enzymes are between 4 and 36 U/L for ALT and 8 and 33 U/L for AST. Persistently high levels suggest ongoing liver inflammation or damage.
Why Enzymes Can Be Normal in Cirrhosis
One reason liver enzymes can appear normal in cirrhosis is due to a “burnt-out” liver. In advanced stages, many liver cells are destroyed and replaced by non-functional scar tissue. With fewer healthy cells remaining, fewer can release enzymes into the bloodstream, even if the remaining tissue is stressed. This means enzyme levels may no longer accurately reflect the extensive scarring and dysfunction present.
The stage of cirrhosis also influences enzyme levels, particularly in compensated versus decompensated cirrhosis. In compensated cirrhosis, the liver, despite significant scarring, can still perform many functions. Individuals in this stage may experience no noticeable symptoms, and their liver enzyme tests might return within normal limits because the remaining tissue adequately compensates for the damage. Conversely, decompensated cirrhosis involves clear symptoms and overt liver failure, where the organ can no longer function properly.
Enzyme levels can fluctuate over time. A single blood test showing normal results might represent a temporary dip in enzyme release, even if levels were elevated previously or will become elevated again. Some underlying causes of cirrhosis may not always present with pronounced elevations. For example, individuals with chronic viral hepatitis or non-alcoholic fatty liver disease can progress to significant liver fibrosis or cirrhosis while maintaining persistently normal aminotransferase levels.
How Cirrhosis is Confirmed
Given that liver enzyme levels alone are not always definitive, diagnosing cirrhosis relies on a comprehensive evaluation involving several diagnostic methods. Imaging studies assess the liver’s structure and identify characteristic changes. Ultrasound, CT scans, and MRI can reveal signs such as liver shrinkage, a nodular or bumpy surface, and indicators of portal hypertension, including an enlarged spleen or varices (enlarged blood vessels). Specialized non-invasive imaging techniques like elastography, including transient elastography or magnetic resonance elastography (MRE), directly measure the stiffness of liver tissue, providing an estimate of fibrosis or scarring.
Liver biopsy is often considered the most definitive method for confirming cirrhosis. This procedure involves taking a small tissue sample from the liver, examined under a microscope to identify characteristic scarring and nodule formation. While not always necessary, a biopsy can be important when other test results are inconclusive or to determine the specific cause of the liver disease.
Beyond ALT and AST, other blood tests provide information about overall liver function. These include measurements of bilirubin, a waste product processed by the liver; albumin, a protein produced by the liver; and the international normalized ratio (INR) or prothrombin time (PT), which assess the blood’s clotting ability. Abnormalities in these markers, such as low albumin, high bilirubin, or impaired clotting, indicate reduced liver function. Clinical signs and symptoms, such as jaundice, fluid accumulation in the abdomen (ascites), or confusion (hepatic encephalopathy), also contribute to the diagnosis, particularly in more advanced cases.
What Normal Enzymes Mean for Cirrhosis Patients
Normal liver enzyme levels in a patient with cirrhosis do not imply the disease is mild or treatment is unnecessary. Cirrhosis represents irreversible scarring of the liver, and this damage can continue to progress even without obvious enzyme elevations.
Ongoing medical monitoring is important for individuals with cirrhosis, regardless of their enzyme levels. This includes regular screening for potential complications, such as liver cancer or the formation of varices, which are enlarged veins prone to bleeding. Comprehensive management involves addressing the underlying cause of cirrhosis and implementing strategies to prevent further liver damage. The prognosis for a person with cirrhosis is more closely linked to the stage of the disease, specifically whether it is compensated or decompensated, rather than solely relying on enzyme levels. A complete clinical picture, integrating all available diagnostic information, is fundamental for accurate assessment and effective management.