Liver function tests (LFTs) are blood tests that provide insights into liver health. They measure various enzymes and proteins that can indicate liver activity or damage. Cirrhosis is a serious condition characterized by extensive scarring of the liver tissue. LFTs can appear normal even when cirrhosis is present, and normal LFT results do not always rule out significant liver disease.
Understanding Liver Function Tests
Common LFTs include alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), and gamma-glutamyl transferase (GGT). These enzymes are typically found within liver cells, and their elevated levels in the bloodstream can signal liver cell damage.
LFTs also measure proteins like albumin, which the liver produces, and bilirubin, a waste product processed by the liver. Albumin levels reflect the liver’s ability to synthesize proteins, while bilirubin levels indicate its capacity to process and excrete waste. These tests primarily indicate liver activity or damage, not its overall functional capacity or structural integrity.
The Stages of Cirrhosis
Cirrhosis represents an advanced stage of liver disease, characterized by irreversible scarring (fibrosis). This scarring replaces healthy liver cells, impeding the liver’s functions and leading to structural changes.
The progression of cirrhosis is categorized into two main stages: compensated and decompensated. In compensated cirrhosis, despite substantial scarring, the liver retains enough functional capacity to perform most of its essential roles. Individuals in this stage may experience no noticeable symptoms, or only mild symptoms such as fatigue, as the liver adapts to the damage.
In contrast, decompensated cirrhosis signifies a more severe stage where the liver can no longer adequately perform its functions. This stage is marked by serious complications, including fluid accumulation in the abdomen (ascites), bleeding from enlarged veins in the esophagus (variceal hemorrhage), confusion due to toxin buildup (hepatic encephalopathy), and yellowing of the skin or eyes (jaundice). The development of these complications indicates that the liver’s functional reserve has been overwhelmed.
When Liver Function Tests Appear Normal
It is possible for liver function tests to appear normal even in the presence of cirrhosis, particularly in its early or compensated stages. This occurs because LFTs, especially the enzyme markers like ALT and AST, primarily reflect ongoing liver cell inflammation or damage. In compensated cirrhosis, the remaining healthy liver cells may still function adequately, or the active inflammatory process might have subsided.
A normal LFT result does not necessarily indicate the absence of significant liver disease or scarring. The tests measure markers of injury, not the extent of scar tissue or architectural distortion. For instance, a person with compensated cirrhosis might have normal ALT and AST levels, even though their liver has considerable scarring. Relying solely on LFTs can overlook the presence of advanced fibrosis or cirrhosis.
Comprehensive Liver Assessment
Given that liver function tests alone are often insufficient for diagnosing or ruling out cirrhosis, a comprehensive approach to liver assessment is necessary. A healthcare professional typically begins with a thorough clinical evaluation, including a detailed medical history and a physical examination to look for signs of liver disease. This initial assessment provides crucial context for further investigations.
Beyond basic blood tests, various specialized diagnostic tools are employed. Imaging techniques, such as ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI), can visualize the liver’s structure, size, and texture, revealing abnormalities like nodularity or signs of portal hypertension. Non-invasive tests like transient elastography (e.g., FibroScan) measure liver stiffness, which correlates with the degree of fibrosis or scarring. While a liver biopsy remains a definitive method for confirming cirrhosis and assessing its severity, it is often reserved for cases where other tests are inconclusive due to its invasive nature. A diagnosis of cirrhosis relies on integrating findings from these diverse methods to provide a complete picture of liver health.