Presentation on theme: "BILIRUBUN METABOLISM AN OVERVIEW"— Presentation transcript:
1 BILIRUBUN METABOLISM AN OVERVIEW Good reference site for abnormal liver function test info.
2 FATE OF RED BLOOD CELLS Life span in blood stream is 60-120 days Senescent RBCs are phagocytosed and/or lysedNormally, lysis occurs extravascularly in the reticuloendothelial system (mainly spleen) subsequent to RBC phagocytosisLysis can also occur intravascularly(in blood stream)
3 NORMAL BILIRUBIN METABOLISM Unconjugated = Fat soluble Conjugated = Water soluble
4 HYPERBILIRUBINEMIAIncreased plasma concentrations of bilirubin (> 3 mg/dL) occurswhen there is an imbalance between its production and excretionRecognized clinically as jaundice
5 Prehepatic (hemolytic) jaundice Results from excess production of bilirubin (beyond the livers ability to conjugate it) following hemolysisExcess RBC lysis is commonly the result of autoimmune disease; hemolytic disease of the newborn (Rh- or ABO- incompatibility); structurally abnormal RBCs (Sickle cell disease); or breakdown of extravasated bloodHigh plasma concentrations of unconjugated* bilirubin (normal concentration ~0.5 mg/dL)*Fat soluble
6 Intrahepatic jaundice Impaired uptake, conjugation, or secretion of bilirubinReflects a generalized liver (hepatocyte) dysfunctionIn this case, hyperbilirubinemia is usually accompanied by other abnormalities in biochemical markers of liver function
7 Posthepatic jaundice Caused by an obstruction of the biliary tree Plasma bilirubin is conjugated, and other biliary metabolites, such as bile acids accumulate in the plasmaCharacterized by pale colored stools (absence of fecal bilirubin or urobilin), and dark urine (increased conjugated bilirubin)In a complete obstruction, urobilin is absent from the urine
8 Diagnoses of Jaundice AST (SGOT)/ ALT (SGPT) = Transaminases ALP = Alkaline Phosphatse
9 Common, particularly in premature infants Neonatal JaundiceCommon, particularly in premature infantsTransient (resolves in the first 10 days)Due to immaturity of the liver enzymesHigh levels of unconjugated bilirubin are toxic to the newborn – cause a type of mental retardation known as kernicterusJaundice within the first 24 hrs of life or which takes longer then 10 days to esolve is usually pathological and needs to be further investigatedCommon, particularly in premature infantsTransient (resolves in the first 10 days)Due to immaturity of the enzymes involved in bilirubin conjugationHigh levels of unconjugated bilirubin are toxic to the newborn –due to its fat solubility it can cross the blood-brain barrier and cause a typeof mental retardation known as kernicterusIf bilirubin levels are judged to be too high,then phototherapy with UV light is used to convertit to a water soluble, non-toxic formIf necessary, exchange blood transfusionis used to remove excess bilirubinPhenobarbital is oftentimes administered toMom prior to an induced labor of apremature infant – crosses the placenta and induces the synthesis of UDP glucuronyl transferaseJaundice within the first 24 hrs of life or whichtakes longer then 10 days to resolve is usuallypathological and needs to be further investigated
11 Overview Patterns of Liver damage Review of individual tests Appraise synthetic functionNon-hepatic causes of abnormal testsSynthesize an approach to evaluation
12 What does the Liver do? A LOT! Detoxifies Poisons Stores and Mobilizes EnergyControls Blood Sugar (Glucose)Regulates GlycogenRegulates Fat StorageAids DigestionProduces BileRegulates Blood ClottingManufacturesClotting factorsOther Blood ProteinsProduces HormonesManufactures Cholesterol Filters BloodDetoxifies PoisonsExternally-Derived PoisonsAlcoholByproducts of MetabolismBilirubinBreaks down DrugsProduces VitaminsVitamin DStores MineralsIronProduces Essential Immune System FactorsMonitors, as Well as Manufactures, Countless other Blood Proteins, to Maintain the Proper Levels of Numerous Chemicals in the Body
13 Liver Function Key Points Produces bileProduces proteinsAlbuminClotting factorsLiver does TOO much for any single test or set of test to determineFocus on the basic test themselves and recognition of basic patterns
14 Markers of Hepatocellular Injury Hepatocytes are damaged so they leak – so these enzymes are HIGHAspartate aminotransferase(AST/ SGOT)Alanine aminotransferase(ALT/ SGPT)Lactate dehydrogenase (LDH)
15 AST:ALT ratio Alcoholic hepatitis Ratio is >1 90% of the time – often 2:1Mechanism thought to be related to B6 depletion in alcoholics which leads to disrupted ALT synthesis and therefore decreased levels.This is NOT SPECIFIC!!Viral Hepatitis: Both ALT AND AST elevatedRatio < 1 70% of the timeMechanism unclear
16 Causes of Hepatocellular Damage A Autoimmune hepatitis – ANA, Anti-smooth muscle ab (ASMA), Anti-Liver and Kidney Mitochondrial Ab. HEP AB Hepatitis BC Hepatitis CD Drugs or toxinsE Ethanol / Hep E (Pregnancy)F Fatty liverG Growths (i.e., tumors)H Hemodynamic disorder(congestive heart failure or “shock liver”)I Inborn errors - iron (hemochromatosis),copper (Wilson's disease) or alpha1-antitrypsin deficiency
17 Level of ElevationGiannini, E. G. et al. CMAJ 2005;172:
18 Key points AST and ALT elevations infer HEPATOCELLULAR DAMAGE NON-SPECIFIC TEST with other causes that can lead to elevationLevels in the 100’s ETOH, 1000’s viral, and 10,000’s toxin related.Ratio can SUGGEST but not diagnose alcoholic hepatitis
19 Markers of Cholestasis/Obstruction Cholestasis (lack of bile flow) results from the blockage of bile ducts or from a disease that impairs bile formation in the liver itself. Back leads to GRADUAL increase in enzymes over the course of days.Alkaline phosphatase (ALP)Gamma-glutamyltransferase (GGT)Bilirubin
20 ALP Originates primarily in Bone and Liver Other sources include intestine, kidney, placenta.Isoenzymes can determine Bone vs LiverMay lag behind symptoms in rising.
21 GGTP (gamma glutamyl transpeptidase): elevated in bile duct disease and alcoholism.
22 Causes of Cholestasis Obstruction Intrahepatic Primary Biliary Cirrhosis – young females. Test: Anti-Mitochondrial Ab (AMA)DRUGS – any number of medications, particularly antibiotics and anti-seizureAny Hepatocellular damage (CONFUSED?The hepatocellular can cause cholestatis, but the necrosis is greater)Critical illnessExtrahepaticCommon duct obstruction (stone/Tumor)Primary Sclerosing Cholangitis – More often males with IBDPancreatic head obstruction (Stone/Tumor)Differentiate – use U/S to look at common bile duct dilation.If non-diagnostic do ERCP then liver bx.
23 Bilirubin Fractions Present in Blood and Urine In Serum As:Measured As:Present in UrineUnconjugated(90%)Albumin-boundIndirect-reacting bilirubinNeverConjugatedUnboundDirect-reacting bilirubinYes, when serum bilirubin exceeds 3-4 mg/dL
24 ACUTE ALCOHOLIC HEPATITIS Pattern of liver test abnormality is hepatocellularAST level is higher than the ALT level but rarely exceeds 400 IU/mLAST is typically in the100 IU/mL to 200 IU/mL range,even in severe disease, andThe ALT may even be normal,even in severe cases“In alcoholic hepatitis AST:ALT ratio is 2:1”
27 Key PointsALP and GGT combined are markers of cholestasis, but other things can make them rise.2 types of Bilirubin, only conjugated excreted in urineCholestasis can be extra or intrahepatic – remember how to differentiate
28 LIVER FUNCTION TESTS Protein production Albumin Clotting Factors Total protein production
29 Albumin 65% of serum protein ½ Life = 3 weeks Low levels can correlate with chronic liver dysfunction.Other reasons to be low?Decrease productionMalnutritionChronic InflammationIncreased LossKidney – Nephrotic SyndromeGI tract – Protein-losing enteropathySkin – Severe burn
30 A/G RATIO:The value of the A/G ratio is not precise due to the countless number of variables in the fractions (Total Globulins and Albumin) associated with various metabolic states.Abnormal A/G ratios usually reflect a general index of liver dysfunction.
31 Clotting Factors Most clotting factors are synthesized in the liver ½ shorter than AlbuminProthrombin Time (PT) is a good functional test – but usually use INR to correct for lab variabilityPT/INR PROLONGED in liver disease
32 Clotting FactorChronic cholestatic disease often have increased INR– Why?Vit K defVit K Fat soluableCholestatic/obustructive so not enough bile secretion so not enough Vit K absorptionHow to differentiate Vit K def from Decreased synthesis?Give Vit K (take hours to correct)Factor V NOT Vit K dependent so can be checked directly
33 Key Points The only liver FUNCTION test are test of PROTEIN PRODUCTION Low albumin due to liver dysfunction implies CHRONIC (>3 week) liver damageAlways differentiate Vit K Def from Decreased liver synthesis in pt with cholestatic disease
34 Further Testing Ultrasound Good to visualize large bile ducts and large masses. Cheap. Non-invasiveUse: ObstructionERCP (Endoscopic Retrograde Cholangio Pancreatography)Visualize smaller bile ducts, ampulla of Vater, and head of pancreas. Provides t issue. Expensive. Highly invasiveLiver Biopsy (rarely done)See hepatic pathology, particularly of the hepatocytes. Gold Standard. Expensive. InvasiveUse: Hepatocelluar
35 Overview of Approach to Liver Tests Think of NON-hepatic causes for abnormalitiesLook at pattern – cholestatic (hepatobiliary) vs hepatocellularLook at tests of FUNCTION for duration of dysfunctionWhat is your DDx?What further testing is needed?See
36 Caveats of Liver ‘Function’ Tests There is NO PERFECT TESTA group of tests is needed in order to ‘infer’ functional liver status.Mixed injury/obstruction patterns are common in REAL LIFE !!DO NOT assume that a NORMAL test result indicates absence of liver disease. (example: AST & ALT can be normal in End Stage Cirrhosis.)
38 Anti-HBsAgHBsAgHBeAgAnti-HBcAgAnti-HBeAgHBV DNA
39 Hepatitis B http://en.wikipedia.org/wiki/Hepatitis_B HBsAg is the surface antigen of the Hepatitis-B-Virus (HBV). It indicates current Hepatitis B infection.HBcAg (core antigen) is a hepatitis B viral protein. It is an indicator of active viral replication; this means the person infected with Hepatitis B can likely transmit the virus on to another person (i.e. the person is infectious). Multiple protein products can be produced from the same DNA sequence. When "ORF Core" and "Pre C" are translated together, the result is "HBeAg".Hepatitis B vaccine is a vaccine developed for the prevention of hepatitis B virus infection. The vaccine contains one of the viral envelope proteins, hepatitis B surface antigen (HBsAg). A course of three (3) vaccine injections are given with the second injection at least one month after the first dose and the third injection given six months after the first dose. Afterward an immune system antibody to HBsAg is established in the bloodstream. The antibody is known as anti-HBsAg. This antibody and immune system memory then provide immunity to hepatitis B infection.
41 Why Genotype? · Genotypes 1, 2 and 3 = North America and Western Europe· Genotype 4 =Africa, Egypt and the Middle East, but is increasingly seen in some parts of Europe·Genotype 5 = Africa and the Middle East· Genotype 6 = Southeast Asia· Genotype 7 = Central Africa2 and 3 are more likely to rsvp to therapy than the others. Current tx is interferon combined with….? Follow the treatment wih the viral load test to measure # of copies made by virus.Only 23% of Hep C patients can expect a cure in the US.
42 Why Genotype? 1. Those with genotypes 2 and 3: Respond better (require only 24 week therapy)2. Genotype 1 to respond poorly to therapy with-alpha interferon or the combination of alpha interferon and ribavirin.3. A 48-week course of combination treatment is typically adequate for those with genotype 1.4. Data are mixed concerning genotype 4, though its response somewhere in between the response of genotypes 2 and 3, and genotype 1.5. Treating genotype 5 shows that its response to combination treatment is similar to those with genotype 1.6. genotype 6 lies at an intermediate level, between that seen with genotype 1 and genotypes 2 or 3.7. Since it has just recently been discovered as having a distinct genetic make-up, the response to standard combination therapy is not yet established for genotype 7.1. Those with genotypes 2 and 3 are almost three times more likely than patients with genotype 1 to respond to therapy with alpha interferon or the combination of alpha interferon and ribavirin.2. A 24-week course of combination treatment is typically adequate for those with genotypes 2 and 3.*3. A 48-week course of combination treatment is typically adequate for those with genotype 1.*4. Data are mixed concerning genotype 4, though its response to combination treatment seems to be somewhere in between the response of genotypes 2 and 3, and genotype 1.5. Recently published research on treating genotype 5 shows that its response to combination treatment is similar to those with genotype 1. However, previous results show that genotype 5 appears to be an easy to treat virus with response rates similar to those of genotypes 2 and 3 after a 48-week course of therapy.6. Preliminary study results show that the response to treatment in those with genotype 6 lies at an intermediate level, between that seen with genotype 1 and genotypes 2 or 3.7. Since it has just recently been discovered as having a distinct genetic make-up, the response to standard combination therapy is not yet established for genotype 7.
43 USA: Prev:4 million Incidence:35,000 to 185,000 Deaths: 10,000-20,000
46 VIRAL LOAD TESTS Measures number copies made by a virus Reported as ‘high’ or ‘low’High: More than 2 million copiesLow: Less than 2 million copies?Log drop: A 10 fold change- take 0ne zero off the end of starting number for each ‘log drop’/’log kill’
47 RIBA Recombinant Immunoblot Assay The EIA anti-HCV reactivity could represent a false-positive reaction, recovery from hepatitis C, or continued virus infection with levels of virus too low to be detectedIf the immunoblot test for anti-HCV is positive, the patient has most likely recovered from hepatitis C and has persistent antibody without virus.If the immunoblot test is negative, the EIA result was probably a false positive.
48 PCR (Polymerase Chain Reaction) Amplification PCR amplification can detect low levels of HCV RNA in serum.Testing for HCV RNA is a reliable way of demonstrating that hepatitis C infection is present and is the most specific test for infection.
49 Genotyping and Serotyping of HCV 6 known genotypes and more than 50 subtypes of hepatitis CHelpful in epidemiology and deciding response to therapyGenotypes 2 and 3 are almost three times more likely to respond to therapy with alpha interferon or the combination of alpha interferon and ribavirin.
50 ELISAEnzyme-Linked ImmunoSorbent Assay, or ELISA, is a biochemical technique used mainly in immunology to detect the presence of an antibody or an antigen in a sample.
51 3 ways to test viral loads: PCR measure the amount of HCV RNA in the blood (can measure very small loads as low as 50 IU/mL)bDNA (Branched –chain DNA)- only measures medium loads above 500 IU/mLTMA (Transcription-mediated amplification) can measure very small amounts (5-10 IU/mL)
52 Remember! Antibodies (Ab) suggests immune response IgM-Ab means acute infectionsIgG-Ab means NO active infection
53 Immunoassay Antibody (Ab) or antibodies to its antigen (Ag) A test that measures the concentration of a substance in a biological liquid:typically serum or urine,uses the reaction of anAntibody (Ab) or antibodiesto its antigen (Ag)
54 X Anti-HBs –ve; HBsAg+; Anti HBc Ag +ve; Anti-HBc IGM Ab +ve Suggests: A. Acute hepatitis BB Chronic hepatitis B-Low infectivityC. Chronic hepatitis B-High infectivityD. Immunized against HBV infection
55 X Anti-HBs -ve; X Anti-HBc IGM Ab –ve; HBsAg detected; Anti HBc Ag +ve;X Anti-HBc IGM Ab –ve;Anti- HBe Ab +ve;Suggests:A. Acute hepatitis BB Chronic hepatitis B-Low infectivityC. Chronic hepatitis B-High infectivityD. Immunized against HBV infection
56 X HBsAg not detected; Anti-HBs +ve; X Anti-HBc IGM Ab –ve; Suggests: A. Acute hepatitis BB Chronic hepatitis B-Low infectivityC. Chronic hepatitis B-High infectivityD. Immunized against HBV infection
57 HBsAg detected; X Anti-HBs not detected; X Anti-HBc IGM Ab not detected; X Anti-HBe Ag not detected Suggests:A. Acute hepatitis BB Chronic hepatitis B-Low infectivityC.Chronic hepatitis B-High infectivityD.Immunized against HBV infection
58 HBsAg not detected;Anti-HBs not detected;Anti-HBc IGM Ab not detected;Suggests:A. Acute hepatitis BB Chronic hepatitis B-Low infectivityC. Chronic hepatitis B-High infectivityD. Immunized against HBV infectionE. Susceptible to HBV infection
64 ? PANCREATIC INSUFFICIENCY Lack of digestive enzymes:presents with symptoms of malabsorption,malnutrition,vitamin deficiencies,weight loss, and is often associated with steatorrhea (loose, fatty, foul-smelling stools).Diabetes may also be present in adults with pancreatic insufficiency.
66 Pancreatitis Amylase- increase after 2-12 hrs peaks at 12-72 hrs Lipase- increase after 4-8 hrs peaks at 24 hrsTrypsin/TrypsinogenComplete Blood Count (including white blood cell count)Comprehensive Metabolic Panel (Bilirubin, liver function tests)GlucoseCalciumMagnesiumC-Reactive Protein