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56 Cards in this Set
- Front
- Back
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Functions of the liver
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-major site for synthesis of proteins, endogenous lipids, and lipoproteins
-major site for metabolism of lipid soluble drugs and other toxic compounds -involved in storage of energy as glycogen -vitamins A, D, B12 -endorcrine organ that synthesizes angiotensinogen and triiodothyronine -site for clearance for many hormones (inuslin, parathyroid hormone, estrogen, cortisol) |
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Purpose of Liver function tests?
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-give indication of hepatic structure, intregity, and function
-measure substances released by damaged tissues -measures substances metabolized/produced by the liver -used for screening, identifying, and monitoring pts with liver disease |
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Liver enzymes include:
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-alkaline phosphatase (ALP)
-Aspartate aminotransferase (AST); formerly SGOT -Alanine Aminotransferase (ALT); formerly SGPT -Lactate dehydrogenase (LDH) -Gamma glutamyltransferases (GGT) |
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How are patterns in enzyme changes determined?
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liver injury determines the pattern
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Cytoplasic enzymes
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LDH
AST ALT |
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Example of cytoplasmic related injury
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cell death resulting in leakage of cytoplasmic enzymes LDH, AST, ALT
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Mitochondrial enzymes
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AST
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Examples of mitochondrial injury
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alcohol rapidly releases mitochondrial AST
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Canalicular
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ALP
GGT |
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Example of canalicular injury
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obstructive process and accumulation of bile acids releases canalicular enzymes ALP and GGT
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ALP
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-alkaline phosphatase
-liver enzyme |
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Where is ALP found?
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-liver, bone, biliary tract, epithelium, intestinal mucose, placenta
-each source has its own isoenzymes |
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What is ALP used for?
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-index of liver and bone disease
-enzyme rises in proportion to new bone cell production -blood levels rise when excretion from the liver is impaired |
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ALP is normally elevated in...
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children due to bone growth
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Liver and biliary tract excrete ALP into the ...
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bile
So if bile ducts are blocked, ALP ends up in the serum |
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Increased ALP suggests:
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-liver tumor or absess
-metastatic disease -alcoholic cirrhosis -drug induced liver dz -biliary tract obstruction -hyperparathyroidism -hepatitis -mononucleosis -bone tumors -pagets dz -fracture healing |
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AST
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-aspartate aminotransferase
-liver enzyme |
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AST elevated in...
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-following MI
-liver disease or injury -liver tumor or absess -cirrhosis -hepatitis -drug or ETOH damage |
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AST is a good indicator of...
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acute liver cell damage
bc levels rise and fall quickly |
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ALT
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-Alanine Aminotransferase
-liver enzyme |
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ALT is found in..
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-liver
-small amts in kidney, heart, and skeletal muscle |
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Elevation in ALT suggests...
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-liver disease
-can help sort out binge drinker from alcoholic |
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ALT vs AST
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-elevated to same degree in hepatitis, mono, drug induced acute liver injury
-ALT less than AST in acute alcoholic liver disease or active cirrhosis -ALT elevated longer than AST d/t longer half life -ALT often used to confirm AST elevations are d/t liver injury |
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GGT
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-Gamma Glutamyltransferase
-liver enzyme |
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Where is GGT found?
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-mainly in liver
-small amounts in biliary tract, heart, intestine, brain, pancreas and spleen |
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GGT is elevated in...
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-active liver disease (acute damage or biliary obstruction)
-tumor -chronic ETOH use and binge drinking |
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GGT is NOT elevated in...
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-bone disease, growth or pregnancy (unlike ALP)
-not significantly elevated with normal ETOH use |
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Differences between ALP, ALT, AST and GGT
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-ALP increases in bone disease, bone growth, and pregnancy whereas others do not
-GGT may help confirm that rise is d/t liver damage -AST is more sensitive thand ALT for acute alcoholic liver disease or active cirrhosis -GGT has same or better sensitivy as ALP for obstruction -GGT has better sensitivity for tumor than ALP -GGT elevated with same frequency as AST for actue liver injury ALT often used to confirm AST elevations are d/t liver injury -ALT and AST elevated to same degree in hepatitis, mono, drug induced acute liver injury |
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Bilirubin basics
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-results from metabolism of heme (found in hemoglobin, myoglobin, and cytochromes
-byproduct of hemolysis (RBC destruction) -small amount in serum is normal -is cleared in liver |
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Unconjugated bilirubin (Indirect)
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-found in serum
-proetin bound -NOT water soluble -cannot get into urine |
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Conjugated bilirubin (Direct)
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-water soluble
-normally excreted in the bile after being processed in the liver |
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Normal ranges of bilirubin:
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Total < 1.5 mg/dl
Direct < 0.4 mg/dl Indirect cannot be measured, must be calculated Take note that there is usually far more unconjugated (indirect) than conjugated (direct) |
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Extra-hepatic biliary tract obstruction
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-common bile duct obstruction (gall stones, carcinoma at the head of pancreas)
-conjugated bilirubin rises initially -as levels of conjugated bilirubin rise, it becomes protein bound and ratio of conjugated to unconjugated approached 1:1 (usually there is far more unconjugated bilirubin) |
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Intra-hepatic biliary tract obstruction
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-from liver cell injury (hepatitis, cirrhosis, drugs, mononucleosis)
-conjugated and unconjugated both rise -conjugated rises d/t blockage of small bile passages between cells -unconjugated rises d/t inability of the liver to conjugate/metabolize |
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Pts >60 with a bilirubin increase:
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Cancer 45%
Gallstones 25% ETOH 10% Meds 10% |
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pts 30-60 with total bilirubin (indirect and direct) increase:
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viral infection 30%
ETOH 30% Gallstones 30% Cancer 10% |
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Pts <30 with bilirubin increase:
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viral >80%
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Normal level of total bilirubin rules out....
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any significant impairment of the excretory function of the liver or excesive hemolysis of RBCs
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Bilirubin: Critical Values
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Newborn >15 mg/dl (treatment is initiated or mental retardation may result)
Adult >12 mg/dl (indicated sever liver problems) |
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kernicterus
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mental retardation secondary to increased bilirubin
To prevent/treate, put under UV light which breaks down bilirubin |
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Hepatic Function Panel
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AST
ALT ALP Total Bilirubin DIrect Bilirubin Total protein Albumin |
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Pancreatic enzymes
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amylase
lipase |
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Amyalse
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-secreted from pancreatic cells into pancreatic duct
-aids in catabolism of carbs in the intestines |
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Amylase test used to ..
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-detect and monitor pancreatitis
-often ordered when pt presents with acute abdominal pain |
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Abnormal values rise and normalize...
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-rise within 12 hours of onset of disease
-clear within 48-72 hours of initial insult (cleared by kidneys) |
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Do abnormal levels of amylase correlate with severity of disease?
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No, levels rise and fall easily - they do not indicate how severe the disease is
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Amylase increases in...
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-pancreatic disease
-biliary disease -renal failure -intestinal obstruction or infarction -obstructed salivery duct |
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Lipase
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-secreted by pancreas into duodenum to break down triglyerides
-excreted by kidney |
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Lipase test is used for..
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acute pancreatitis
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Lipase increases in...
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-pancreatic disease
-biliary disease -renal failure -intestinal obstruction or infarction |
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Lipase elevation and normalization
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-peaks at 24-48 hours
-normalizes in 7-10 days |
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Lipase vs Amylase
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-lipase levels parallel the rise in amylase but rise later (peak 24-48 hours vs 12 hrs)
-lipse levels normalize later than amylase (7-10 days vs 48-72 hrs) -lipase is less sensitive but more specific then amylase as indicator for pancreatitis -amylase will rise with blocked salivary duct as well |
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Serum immunoreactive trypsin
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-produced only by pancreas
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SIT increases with...
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pancreatitis (95% of the time)
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Advantages of SIT
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VERy specific and VERY sensitive (~95%)
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Disadvantages of SIT
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not widely available
time delay in results |
