Complete blood count
In hepatobiliary system diseases, complete blood count parameters change strictly depending on the duration and nature of the pathological process.
- Acute inflammatory processes: acute cholecystitis or acute alcoholic hepatitis exhibits a typical inflammatory pattern. An elevated leukocyte count (leukocytosis) and a significant increase in the erythrocyte sedimentation rate (ESR) are recorded in the blood.
- Chronic viral processes: long-standing diseases, such as chronic viral hepatitis, lead to pronounced suppression of hematopoiesis lines. This manifests as a decreased leukocyte count (leukopenia) and platelet count (thrombocytopenia). Meanwhile, accelerated ESR persists as a marker of chronic pathology.
Biochemistry: cytolysis and cholestasis syndromes
Biochemical analysis is the primary tool for assessing hepatobiliary function. The main focus is on bilirubin and specific enzymes.
Cytolysis syndrome indicates the destruction of hepatocyte membranes and the release of enzymes into the systemic circulation:
- Alanine aminotransferase (ALT): localized in the cytoplasm of hepatocytes. It exhibits extremely high specificity specifically for liver tissue. In most liver diseases, the increase in ALT significantly outpaces AST.
- Aspartate aminotransferase (AST): located inside cell mitochondria. Its specificity is lower, as the enzyme is also present in the heart, kidneys, brain, and muscles. A sharp spike in AST indicates severe necrotic organ damage (typical of severe toxic or acute viral hepatitis). An exception is alcoholic liver disease, in which AST activity always increases more than ALT.
Cholestasis syndrome encompasses enzymes indicating problems with bile outflow:
- Alkaline phosphatase (ALP): demonstrates maximum elevation in bile duct damage and bile stasis. However, the enzyme can also rise due to extrahepatic causes (hypernephroma, bronchogenic carcinoma, Hodgkin's lymphoma).
- Gamma-glutamyl transferase (GGT): a marker of liver, biliary tract, and pancreatic disorders. The combination of high GGT and AST levels is considered a reliable laboratory sign of alcohol abuse.
Synthetic function and metabolism
The assessment of the protein-synthetic function of the liver is performed using protein electrophoresis.
- Dysproteinemia: disruption of the normal balance of protein fractions, most commonly manifesting as hypergammaglobulinemia (an increase in $\gamma$-globulins).
- Hypoproteinemia: a drop in total protein levels, primarily at the expense of albumins. It is a marker of severe pathology and depletion of liver reserves.
- Hyperproteinemia: a rare phenomenon characteristic of hepatitis with a strong autoimmune component.
The severity of liver failure is determined by a decrease in synthesis: albumin, prothrombin, and cholesterol levels drop. In cholestasis, conversely, cholesterol accumulates in the blood.
Trace element metabolism is also important. Excess free copper and iron are toxic to the parenchyma. For example, in genetic Wilson's disease, a classic triad is identified: high copper levels, low ceruloplasmin, and severe liver damage.
Immunological and virological diagnostics
Laboratory investigation of the causes of the disease relies on immune responses and the detection of pathogen genomes.
Nonspecific immune responses include changes in the levels of immunoglobulins, complement, and circulating immune complexes (CICs). To clarify the etiology, specific markers are sought:
- Alcoholic damage is often accompanied by an increase in IgA class immunoglobulins.
- Autoimmune hepatitis is confirmed by high titers of antinuclear antibodies (ANA) and anti-smooth muscle antibodies.
- Primary biliary cholangitis is characterized by the presence of antimitochondrial antibodies (AMA).
PCR is the modern standard for detecting viral hepatitis (A, B, C, D). The method detects the genetic material of viruses, allows for the evaluation of viral load (degree of viremia) and genotyping, which is critical for selecting antiviral therapy. Markers of active reproduction (replication) of the hepatitis B virus include: HBV-DNA, DNA polymerase, HBeAg, and anti-HBc IgM antibodies.
Briefly: answers to topical questions
Which laboratory parameters decrease in hepatocellular failure?
In hepatocellular failure, parameters reflecting impaired synthetic function of the liver decrease:
- total protein;
- albumin — the decrease in total protein occurs predominantly at the expense of albumins;
- cholesterol;
- prothrombin and prothrombin index (PTI);
- coagulogram parameters: fibrinogen, proconvertin.
Which biochemical markers are specific for alcoholic liver disease?
There are no absolute specific laboratory markers of alcoholism, but alcoholic liver disease and chronic alcohol intoxication are characterized by a set of abnormalities:
- AST increases more than ALT;
- the combination of high GGT and AST activity is considered a marker of occult alcohol abuse;
- GGT is elevated more than alkaline phosphatase;
- a high level of IgA is often detected;
- an increase in uric acid is possible;
- HDL accounts for more than 25% of the total cholesterol level.
What laboratory parameters are included in the mesenchymal liver inflammation syndrome?
The laboratory syndrome of mesenchymal liver inflammation includes parameters reflecting the activation of the immune system and mesenchymal-stromal elements of the liver. An increase is characteristic in:
- acute-phase indicators — CRP, ESR, acute-phase proteins;
- immunoglobulins (Igs);
- the $\gamma$-globulin fraction;
- thymol turbidity test.
What is the De Ritis ratio and what is its normal value?
The De Ritis ratio is a laboratory diagnostic indicator reflecting the ratio of serum transaminase activities: aspartate aminotransferase (AST) to alanine aminotransferase (ALT). This index is used for the differential diagnosis of liver and myocardial diseases. Normally, the physiological ratio of these enzyme activities is $1.33 \pm 0.42$ (approximately 1.3).
Mnemonic for transaminases: ALT is localized in the cytoplasm (L - Light damage), AST is hidden in the mitochondria (S - Severe necrosis). In alcoholism, AST is always higher than ALT.
Class and exam questions
How to distinguish hepatic failure from cholestasis syndrome using a biochemical blood test?
The main differential criterion is the cholesterol level. In liver failure, synthetic function drops, and cholesterol decreases. In cholestasis (bile stasis), its concentration in the blood, conversely, increases.
Why is it so important to evaluate protein fractions in the diagnosis of hepatitis?
Protein electrophoresis reveals dysproteinemia. A decrease in albumins indicates a failure of liver functions, while an increase in $\gamma$-globulins or general hyperproteinemia indicates active inflammation or an autoimmune process.
Why is genotyping and viral load assessment necessary in viral hepatitis?
Determining the exact viral genotype (especially C and B) and the concentration of viral particles in the blood is necessary for the clinician to correctly select drugs and antiviral therapy tactics.
What else to study on this topic
- Bilirubin metabolism and differential diagnosis of jaundice
- Mechanisms of development of hepatic encephalopathy
- Coagulogram changes in liver pathologies
- Instrumental diagnostic methods for the hepatobiliary zone
- The role of circulating immune complexes (CIC) in the pathogenesis of hepatitis
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