Cirrhosis is a chronic and progressive liver disease characterized by the replacement of normal liver tissue with scar tissue, known as fibrosis, and the formation of regenerative nodules. These permanent structural changes impair the liver’s ability to function properly as damage accumulates over time.
Healthy Liver Architecture
A healthy liver has an organized internal structure, arranged into microscopic units called lobules. These lobules contain rows of liver cells, hepatocytes, radiating from a central vein. Blood enters through branches of the hepatic artery and portal vein, flowing through specialized capillaries called sinusoids that separate hepatocyte cords. This arrangement allows for efficient blood processing and bile production.
Hallmark Morphological Changes
The defining characteristic of cirrhotic morphology is extensive fibrosis, where scar tissue replaces healthy liver parenchyma. This alters the liver’s normal, smooth surface, making it nodular. Fibrous bands can bridge between portal tracts or connect them to central veins, disrupting the liver’s internal framework.
Accompanying fibrosis is the formation of regenerative nodules, clumps of hepatocytes attempting to regenerate. These nodules result from cycles of hepatocyte damage and repair. Cirrhosis can be classified based on the size of these nodules; micronodular cirrhosis features uniform nodules generally less than 3 mm in diameter, while macronodular cirrhosis involves larger, irregular nodules exceeding 3 mm. This combination of widespread fibrosis and nodule formation distorts the liver’s internal architecture, replacing its organized lobular structure with a disorganized, scarred landscape.
Mechanisms Behind Structural Alterations
Structural changes in cirrhosis stem from continuous liver injury, inflammation, and abnormal wound healing. Chronic damage to hepatocytes can be triggered by various factors. This sustained injury activates hepatic stellate cells, which then produce excessive extracellular matrix proteins, like collagen, forming fibrous bands.
Common causes include chronic viral hepatitis (Hepatitis B and C) and long-term alcohol abuse. Non-alcoholic fatty liver disease (NAFLD), particularly its more severe form, non-alcoholic steatohepatitis (NASH), is a growing cause due to inflammation and fat accumulation. Autoimmune liver diseases can also trigger chronic inflammation and fibrosis.
Impact of Altered Morphology on Liver Function
Extensive fibrosis and regenerative nodules impede the liver’s many functions. Scar tissue and nodules compress hepatic sinusoids and central veins, increasing resistance to blood flow. This leads to portal hypertension, where blood pressure in the portal vein system becomes abnormally high. Consequently, blood can back up into other organs, causing complications like fluid accumulation in the abdomen (ascites).
The replacement of healthy tissue by non-functional scar tissue and inefficient regeneration reduces the liver’s working capacity. This impairs its ability to detoxify harmful substances, such as ammonia, which can accumulate and affect brain function. The liver’s capacity to synthesize essential proteins, including albumin and blood clotting factors, is also compromised, leading to issues like easy bruising and fluid imbalances. Problems with bile production and flow can also arise, affecting digestion and nutrient absorption.
Visualizing and Diagnosing Cirrhotic Morphology
Detecting cirrhotic morphology involves imaging techniques and direct tissue examination. Imaging modalities like ultrasound, computed tomography (CT) scans, and magnetic resonance imaging (MRI) can reveal characteristic changes in the liver’s appearance. These may include altered liver size, an irregular or nodular surface, and signs of portal hypertension like an enlarged spleen or dilated portal veins.
Liver biopsy remains a key method for directly visualizing the microscopic changes of cirrhosis. A small tissue sample is examined under a microscope to confirm fibrosis, assess its extent, and identify regenerative nodules. While invasive, biopsy provides detailed histological information. Non-invasive methods, such as elastography, also assess liver stiffness, which correlates with fibrosis. These techniques measure how quickly shear waves travel through the liver, indicating its hardness.