Chronic Liver Disease Flashcards
Stimuli for stellate cell activation and transdifferentiation
- Chronic inflammation and associated cytokines
- Cytokines from Kupffer cells, endothelial cells, hepatocytes, and bile duct epithelial cells
- In response to change in ECM composition
- Direct stimulation by toxins
Where is scar laid in fibrosis?
Usually in the space of Disse in a lobular pattern
Liver fibrosis diagram
Do patients with acute liver failure tend to get fibrosis?
No! Despite the presence of many of the same stimuli.
This may be related to the chromatin state of the stellate cells.
In a fibrotic liver, there is an equilibrium between. . .
. . . fibrosis and regeneration.
The balance in active disease favors the former and with remission of disease the latter is favored.
However, once this progresses to full cirrhosis, it is irreversible.
Cirrhosis
- The histological development of regenerative nodules surrounded by fibrous bands in response to chronic liver injury that leads to portal hypertension and end stage liver disease
- Develops as a result of the combined effect of ongoing liver injury, hepatocyte death, scarring, and regeneration
Histologic progression of liver fibrosis
Effects of fibrosis on sinusoids
Defenestration of sinusoidal endothelial cells and ultimately sinusoidal constriction (increased intrahepatic vascular resistance)
Splanchnic circulation
Hepatic portal system
Hepatic vasculature
- High-compliance, low-resistance system
- Accomadates a large volume following a meal without substantially increasing portal pressure
- The hepatic sinusoids are highly permeable because they lack a proper basement membrane and because the endothelial cells that line the sinusoids contain fenestrae
Diagram of hepatic sinusoid layers in normal liver versus cirrhotic liver
In the United States, ___ is by far the most common etiology of portal hypertension
In the United States, cirrhosis is by far the most common etiology of portal hypertension
In cirrhosis, portal hypertension is the result of two major factors:
- Increased resistance to portal blood flow
- Increase in portal venous inflow
Reasons for portal hypertension in cirrhosis
- Structural changes occur when there is distortion of the liver microcirculation by fibrosis, nodules, angiogenesis, and vascular occlusion in response to increases in flow and shear stress
-
Contraction of activated hepatic stellate cells that surround hepatic sinusoids
- Too little Nitric oxide or too much Endothelin I can lead to increased resistance through the hepatic microcirculation
- Angiotensin II is a particularly strong constrictor of stellate cells and is increased abundance during cirrhosis due to systemic sympathetic hyperactivity
Reasons for increased portal venous flow in cirrhosis
- Hyperdynamic circulation in cirrhosis is characterized by peripheral and splanchnic vasodilatation, and increased cardiac output to maintain near normal blood pressure.
- NO-mediated relaxation of splanchnic arterioles leads to splanchnic vasodilation and splanchnic hyperemia
- Result is increased flow into the portal system, exacerbating portal hypertension
In cirrhosis, the picture inside the liver is characterized by ___ while the picture outside the liver is characterized by ___.
In cirrhosis, the picture inside the liver is characterized by vasoconstriction while the picture outside the liver is characterized by vasodilation.
Categories of portal hypertension
- Pre-hepatic
- Intrahepatic pre-sinusoidal
- Intrahepatic sinusoidal
- Intrahepatic post-sinusoidal
- Post-hepatic
Portal pressure gradient
- Pressure gradient between the portal vein and the IVC
- Normal range 1-5 mmHg
- The larger the gradient, the more severe the portal hypertension and the more likely complications of cirrhosis
- Hepatic Venous Pressure Gradient (HVPG) used as surrogate for portal pressure gradient
Measuring pressures to assess portal hypertension
- FHVP = Free Hepatic Vein pressure: Balloon deflated in hepatic vein 2-4 cm beyond its connection to the IVC
- WHVP = Wedged HV Pressure (surrogate for portal pressure in cirrhosis): Balloon inflated and occluding in small hepatic veins
- HVPG= Hepatic Venous Pressure Gradient = the difference between the WHVP and FHVP. Represents the pressure gradient between the portal vein and the intra-abdominal IVC.
HVPG range
- Normal 1-5 mmHg
- HVPG ≥10 mmHg is associated with varices
- HVPG >12 mm Hg is associated with a higher risk of variceal hemorrhage
Causes of cirrhosis
- Hepatitis C
- Alcoholic liver disease
- NAFLD
- Hepatitis B
- Hemochromatosis
- Less common causes, including many autoimmune fibrosing disorders
Physical findings of cirrhosis secondary to altered liver function
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Impaired estrogen metabolism and consequent hyperestrogenemia
- In male patients, palmar erythema (intense red coloration of thenar and hypothenar eminences, a reflection of local vasodilatation) and spider angiomas of the skin may develop
- Hypogonadism and gynecomastia
- Hypogonadism may also occur in women due to suppressed LH/FSH
Clubbing in cirrhosis
Clubbing of the fingernails may result from the presence of arteriovenous shunts in the lung as a result of portal hypertension.
Jaundice pruritis
Jaundice, when chronic, can lead to pruritus the intensity of which can be profound. Some patients may even scratch their skin raw and risk repeated bouts of potentially lifethreatening infection
Splenomegaly in cirrhosis
Any longstanding portal hypertension may cause splenomegaly
The massive splenomegaly may secondarily induce hematologic abnormalities attributable to hypersplenism, such as thrombocytopenia or even pancytopenia.