Liver Flashcards
What are lobules?
They are the functional unit of the liver
- Centered on a branch of the hepatic vein
- Interconnected by small ducts
- Contain hepatocytes, separated by sinusoids
- Portal triads (contains vessels that connect to hepatic vein, artery, and bile ducts)
What is the hepatic duct?
- Transports bile produced by liver cells to the gallbladder and duodenum
What does the blood flow to the liver look like?
- Venous flow from portal vein (from GI to liver)
- Arterial flow from hepatic artery (recieves 25% of the cardiac output)
- Venous and arterial flow mixes in the blood and leaves via the hepatic vein
What are the four categories of major liver functions?
- Excretion (bile)
- Metabolism (Bilirubin, drugs, nutrients, hormones)
- Storage (vitamins/minerals (B12, iron), CHO
- Synthesis (plasma proteins, coagulation factors, other transport proteins)
What is the function of the gallbladder?
Stores and concentrated bile
Gallbladder releases bile in response to stimulation by food (cholestatic kinase)
Bile helps emulsify fats and improve elimination of fat-soluble waste
Is bile returned to the body after it has been secreted, or is it all excreted?
95% of bile acids are reabsorbed (enterohepatic recirculation)
Liver disease can impact bile recycling due to reduced enterohepatic recirculation
What is bilirubin?
It is the end product of heme degradation
Insoluble bilirubin = bound to albumin
Direct bilirubin = glucoronidated in liver and is excreted in the bile
What is fulminant liver failure?
This occurs when an acute and severe form of liver injury results in insufficient residual hepatocytes to maintain minimal essential liver functions
This is an irreversible type of liver injury
Review slide 13 for the patterns of hepatocellular injury (appreciate bifurcation)
What are the etiologies of hepatic injury?
- Viral
- Drugs
- Environmental toxins
- Alcohol
What are the main types of hepatic injury?
- Cholestasis
- Hepatocellular
What is cholestasis?
A failure of normal amounts of bile to reach the duodenum
This results in an accumulation of bile in liver cells and biliary passages (Intra vs extrahepatic)
What are some causes for cholestasis?
- Primary biliary cholangitis (PBC)
- Primary sclerosing cholangitis (PSC)
- Cholelithiasis (gall stones)
- Tumour
- Alcohol or drug related causes
What is primary biliary cholangitis (PBC)?
It is caused by the slow, immune-mediated destruction of small bile ducts within the liver
Leading cause of liver transplant for women in Canada
What is primary sclerosing cholangitis (PSC)?
It involves progressive inflammation and fibrosis affecting any part of the biliary tree
Leads to progressive destruction of the bile ducts
What are some symptoms of cholestatic syndrome?
- Pruritis
- Jaundice
- Dark Urine
- Light coloured stools
- Steatorrhea (Fatty stools)
- Xanthoma and xanthelasma (growths under skin due to bile deposition under the surface)
- Hepatomegaly
- Features specific to disease
What is the main therapeutic option used to treat cholealithiasis?
Ursodiol (a naturally occurring bile acid)
Works by decreasing cholesterol saturation. Result in gradual dissolution of stones in 30-40% of patients
Can also be used in cholestasis such as PBC or PSC
What are some treatment options for pruritis in liver disease?
- Cholestyramine (benefit seen in 90% of patients, but needs to be continued as long as there is pruritis)
- Antihistamines (likely due to sedation)
- Naltrexone, rifampin, sertraline (if pruritis is refractory)`
What is hepatocellular damage?
Direct damage to hepatocytes
What are some causes of hepatocellular damage?
- Toxic agents (alcohol, drugs, toxins)
- Infections (hepatitis)
- Longstanding cholestasis
- Ischemic injury
- Other diseases (autoimmune, iron overload)
What factors impact the severity of hepatocellular damage?
- Duration of assault
- Intensity of assault (ex. fulminant hepatic failure)
What are some indicators for hepatocellular damage and destruction?
- Elevated AST and ALT because the contents of hepatocytes have been released into the blood
What is involved in liver enzyme measurement?
The enzymes tested in liver enzyme measurement are released into circulation after injury
ALP, AST, ALT, GGT
What enzymes are indicators for cholestatic injury?
- ALP
- GGT (non-specfic but confirms liver injury)
If ALP and GGT are both high, there is high certainty there is some type of cholestatic injury
What enzymes are indicators for hepatocellular injury?
Increases in Aminotransferases (ALT and AST)
- ALT is more specific than AST
- Often increase before symptoms manifest (can deal with hepatic injury at a less severe state)
What are some examples of liver function tests?
A. Albumin levels
B. Bilirubin
C. Clotting (prothrombin time)
What happens to albumin in patients with liver disease?
- Edema or ascities (due to reduced oncotic pressure)
- Effects on calcium and highly bound drugs like phenytoin
- Reduction in albumin is delayed because it has a 20 day lifespan
What are some symptoms of bilirubin accumulation?
- Deposits in skin and tissues
- Dark urine, pale stools, yellow skin
What are some causes for bilirubin accumualtion in liver disease?
- Obstruction (cholestasis)
- Impaired metabolism (hepatocellular)
- Excessive production due to hemolytic anemia
What are some properties of unconjugated bilirubin?
- Bound to albumin
- Water-soluble
- Indirect bilirubin
What are some properties of conjugated bilirubin?
- Conjugated by liver (via glucoronidation)
- Soluble in water
- Direct bilirubin
What happens to prothrombin time in patients with liver disease?
- Reduced production of clotting factors (increased PT)
- Changes in INR are seen when patient has lost 80% of liver function
What are the main 7 liver laboratory tests?
Liver enzymes:
1. Hepatocellular enzymes
- AST
- ALT
- Cholestatic enzymes
- ALP
- GGT
Liver function:
- Bilirubin
- Albumin
- INR/PTT
Review slide 33 to 37 for practice with interpreting liver lab values
Probably will come on the exam
Is the magnitude of liver function and enzyme values associated with severity of disease?
The magnitude of the values may not be associated with liver disease severity
Trends in liver enzyme and function tests are more important vs single point values
What are the main six complications of cirrhosis?
- Portal HTN
- Ascites
- SBP
- Hepatorenal syndrome
- Varices
- Encephalopathy
What is cirrhosis?
A chronic diffuse disease characterized by fibrosis and nodular formation
ex. long-standing alcohol use results in a hard, shrinken, and nodular liver
What is the only cure for cirrhosis?
Liver transplant
What are some types of cirrhosis?
- Alcohol-related liver disease (ALD)
- Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD), used to be known as NAFLD (often caused by insulin resistance and metabolic syndrome)
- Metabolic Dysfunction-Associated Steatohepatitis (MASH)
What is the current alcohol consumption reccomendations?
All levels of alcohol consumption are associated with some risk, so drinking less is better for everyone
There is a continuum of risk in healthy individuals
How is cirrhosis diagnosed?
- Biochemical markers (liver enzymes + ABCs)
- Scoring systems (FIB-4, uses age, platelet count, AST, and ALT to estimate amount of scarring)
- Abdominal ultrasound (first imaging modality recommended)
- Elastogrpahy (Fibroscan, non-invasive)
- Liver Biopsy (definitive diagnosis of underlying cause of cirrhosis, invasive)
What are the consequences of cirrhosis?
- Reduced functioning liver tissue (impaired function and diminished reserve)
- Portal HTN
- Patients will die 5-15 years after diagnosis of cirrhosis
What are some treatment options for cirrhosis?
- Treat underlying disease
- Treat complications of cirrhosis
- Liver transplantation
What does compensated cirrhosis look like?
- Body functions fairly well despite scarring of the liver (may be asymptomatic)
- Non-specific symptoms (anorexia, weight loss, weakness, NV, GI upset, muscle wasting)
What does decompensated cirrhosis look like?
- Severe scarring and disruption of function
- Symptoms: confusion, edema, fatigue, bleeding
- Abnormal LFTs
- Abnormal exam (signs of chronic liver disease)
What happens when the the portal system has obstructed blood flow?
- Opens detours between the portal and systemic circulation
- Blood is diverted around the liver rather than filtered through the liver
- Portal blood bypasses the liver and directly enters systemic circulation
What is portal HTN?
It results from increase in resistance to portal flow and increase in portal venous inflow
How does the body compenate for portal HTN?
- Splanchnic dilation (results in under-perfusion of renal system)
- To deal with this under-perfusion, RAAS is activated and causes fluid overload
- Fluid overload causes backflow and further widens the venous channels that connect the portal and systemic circulation
What is splenomegaly?
A consequence of portal HTN
The spleen will enlarge by 3-6 times its normal size caused by sequestration and destruction of RBCs (causes anemia)
What are the consequences of portal-to-systemic shunting?
Effectively portal blood is bypassing the liver
1. Metabolites/toxins in the blood have not been processed by the liver first
2. Increased sensitivity to noxious substances absorbed from the GI tract
3. Malabsorption of fat in the stool (reduction in bile flow)
4. Contributes to all complications as well (ascites, SBP, varices, hepatorenal sx)
What is ascites?
It is a collection of fluid in the peritoneal cavity
Can cause massive distention (very uncomfortable to patient)
What is the pathogenesis of ascites?
- Hydrostatic pressure (due to fluid overload from RAAS activation)
- Hypoalbuminemia (reduced oncotic pressure)
- Renal retention of Na+ and water
What is the role of serum-ascites albumin gradient (SAAG) test in liver disease?
It is used in patients with ascites to determine cause of swelling
If greater than 11g/L = portal HTN
If lesser than 11g/L = other likely causes (non-liver disease)
What is the treatment goal in ascites?
- Remove abdominal fluid
- Prevent symptoms and maintain resonable quality of life
What are some treatment options for ascites?
- Salt restriction
- Diuresis
- Paracentesis (drawing fluid through needle)
- TIPS (shunt implant)
- Liver transplant
What does salt restriction in ascites look like?
Less than 2g/day, if Na+ is very high then fluid restriction can be considered
What are the diuretic choices in ascites treatment?
- Spironolactone (1st line)
- Furosemide (adjunct)
What is paracentesis?
Aspiraton of peritoneal flui with a needle (provides immediate relief, but it is temporary)
Albumin can also be given as adjunt to help improve oncotic pressure
There is a non-zero risk for abdominal perforation and infection
What is TIPS in ascites treatment?
Transjugular Intrahepatic Portosystemic Shunt
This implant helps reduce portal HTN by redirecting some of the portal flow to the hepatic vein
What dose of spironolactone used in cirrhosis (ascites management)?
A high dose is used (100mg)
What is the mechanism of action for spironolactone?
Inhibits effects of aldosterone (RAAS activity)
Watch for side effects (hyperkalemia, dehydration, gynecomastia)
How should a spironolactone-furosemide combo therapy be dosed for ascites management?
Usual regimen: spironolactone 100mg + furosemide 40mg
Maintain 100:40 ratio if dose needs to me increased to a max dose of spironolactone 400mg + furosemide 160mg
Metolazone (TZD) can be used if ascites is refractory to spironolactone and furosemide
What are some monitoring tips for diuretics use in ascites treatment?
- Monitoring is important
- SCr, Na, K
- Weight and BP (helps track fluid overload)
What is refractory ascites?
Patient is unresponsive to sodium-restricted diet and high dose diuretic treatment (spirono+furo)
Ascites recurs rapidly after a therapeutic paracentesis and high-dose diuretics
AVOID NSAIDs (turns diuretic sensitve patients to refractory)
How is refractory ascites treated?
- Serial therapeutic paracentesis (+/- albumin)
- Transjugular intrahepatic portasystemic shunt (TIPS)
- Liver transplantation
What are the principles of therapy for ascites?
- Patients should monitor daily weights (gradual weight loss is the goal)
- If no response to diuretics, check urinary sodium
- Monitor SCr, Na+, K+
- Monitor other complications (ex. SBP)
What is spontaneous bacterial peritonitis (SBP)?
It is an infection in ascitic fluid without obvious cause
Caused by bacterial translocation from GI tract to bloodstream and other extraintestinal sites
Is spontaneous bacterial peritonitis a relatively benign condition?
No, mortality rates are high so diagnostic paracentesis and empiric antibiotic treatment is started
What are the most common pathogens found in spontaneous bacterial peritonitis infections?
E. Coli
Klebsiella pneumoniae
Streptococcus pneumoniae
How is spontaneous bacterial peritonitis treated?
Community acquired:
- Cefotaxime or Ceftriaxone x 5days
Nosocomial acquired:
- Piperacillin/tazobactam
- Meropenem+/-vancomycin
Albumin infusions may be adjunct
What patients groups should be given prophylaxis for spontaneous bacterial peritonitis?
- Patients that have survived an episode of spontaneous bacterial peritonitis (secondary prophylaxis)
- Patients at high risk (low protein ascites, variceal hemmorhage) (primary prophylaxis)
What are some prophylactic agents used for spontaneous bacterial peritonitis?
Norfloxacin, septra or ciprofloxacin
What is hepatorenal syndrome?
It is renal failure in patients with severe liver disease. They usually also have massive, tense ascites
Characterized by severe vascoconstriction of the renal circulation (no pathological changes to kidney itself)
What are some treatment options for hepatorenal syndrome?
- Stop diuretics
- Avoid all potential nephrotoxins such as NSAIDs and aminoglycosides