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USMLE STEP 1 > Liver > Flashcards

Liver Flashcards

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USMLE® Step 1 flashcards
1
Q

First sign of jaundice

A

scleral icterus

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2
Q

Kernicterus

A

Deposition of fat-soluble unconjugated bilirubin in the basal ganglia

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3
Q

RBC lifespan

A

About 120 days

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4
Q

When does jaundice begin to appear?

A

Serum bilirubin of above 2.5 mg/dL

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5
Q

Where is heme metabolized?

A

Phagocytes of the reticuloendothelial system: mostly macrophages in the spleen and Kupffer cells of the liver

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6
Q

Heme oxygenase function

A

Libeates chelated iron from heme and equimolar carbon monoxide (exhaled). This yields biliverdin.

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7
Q

Biliverdin reductase

A

Reduces biliverdin to bilirubin, releasing a carbon monoxide molecule

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8
Q

Transport of unconjugated bilirubin to hepatocytes

A

Carried by albumin to the space of Disse. Taken into the basolateral aspect of the hepatocyte by organic anion transporting polypeptide family.

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9
Q

Conjugation of bilirubin

A

Conjugated to glucuronic acid by UDP glucuronyl transferase (UGT) at two different propionic acid side chains to form bilirubin diglucuronide. If overwhelmed, the system can instead make bilirubin monoglucoronide.

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10
Q

Transport of conjugated bilirubin away from hepatocyte

A

Leaves the hepatocyte to enter bile canaliculi through the MRP2 (ATP-bind cassette familly Abcc2). From there, it enters the bile duct and is stored in the gallbladder.

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11
Q

Direct bilirubin

A

A measure of conjugated bilirubin in the serum

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12
Q

Bacterial metabolism of bilirubin

A

Deconjugated by enteric flora in the colon and metabolized further by anaerobes. Converted to urobilinogen (water-soluble).

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13
Q

What happens to urobilinogen?

A

Some of it is excreted in stool, giving stool its dark color. Some reenters enterohepatic circulation. It also contributes to the yellow color of urine (urobilin).

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14
Q

Jaundice in the newborn DDx

A
  • Biliary atresia (most common cause, CB)
  • Rh incompatibility (UCB)
  • Crigler-Najjar Type 1 (severe, UCB)
  • Crigler-Najjar Type 2 (mild, UCB)
  • Physiological jaundice of the newborn (UCB)
  • Gilbert syndrome (UCB)
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15
Q

Treatment for unconjugated bilirubinemia

A

Phototherapy (especially transient jaundice of the newborn)

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16
Q

Physiologic jaundice of the newborn

A

transiently low UGT activity. Increased unconjugated bilirubin. May result in kernicterus. Treatment is phototherapy.

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17
Q

Role of phototherapy

A

To make unconjugated bilirubin water soluble

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18
Q

Gilbert syndrome

A

Autosomal recessive, due to polymorphism resulting in TA insertion in the promoter TATA element of UGT1A1. Mildly low UGT activity, resulting in unconjugated bilirubinemia and mild jaundice/scleral icterus in situations of severe stress.

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19
Q

Crigler-Najjar type I

A

Absence of UGT, resulting in unconjugated bilirubinemia and kerniticus (usually fatal). The only treatment is liver transplant.

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20
Q

Crigler-Najjar type II

A

Reduction of UGT to about 10% of normal levels, producing milder symptoms that type II

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21
Q

Dubin-Johnson syndrome

A

Conjugated bilirubinemia due to defective MRP2. Benign except for dark discoloration of liver. Autosomal recessive on chromosome 10. Serum bilirubin 2-5 mg/dL.

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22
Q

Rotor syndrome

A

Similar to Dubin-Johnson, but with normal liver appearance. Conjugated bilirubinemia due to defective OATP1B1/OATP1B3 transporters. Serum bilirubin 3-8 mg/dL. Autosomal recessive on chromosome 12.

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23
Q

Biliary tract obstruction presentation

A

increased conjugated bilirubin, decreased urobilinogen, increased ALP, dark urine, pale stool, pruritus, hypercholesterolemia with xanthomas, malabsorption of fat-soluble vitamins

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24
Q

Normal serum bilirubin (men)

A

0.3-1.7

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25
Q

Normal serum bilirubin (women)

A

0.2-1.2

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26
Q

Serum bilirubin in Crigler-Najjar type I

A

20-50 mg/dL (below 20 in type II)

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27
Q

Average peak of serum bilirubin in a full-term infant

A

5-6 mg/dL

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28
Q

Pigment stone formation

A

In infection, bacteria in the bile duct deconjugate bilirubin. It precipitates in its less soluble unconjugated form and complexes with calcium in the bile, forming calcium bilirubinate.

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29
Q

Reye syndrome- etiology

A

Impairment of oxidative phosphorylation and beta-oxidation of fatty acids in the liver, usually related to viral infection or aspirin

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30
Q

Acute liver failure- definition

A

Severe liver injury resulting in coagulopathy and mental status change with no previous liver disease and a duration of less than 6 months

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31
Q

Hepatic failure classification

A

Interval between onset of jaundice and start of encephalopathy.

  • Hyperacute = within a week
  • Acute = within a month
  • Subacute = within 2 months
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32
Q

Benign mechanisms of acetaminophen metabolism

A

Sulfation and glucoronidation

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33
Q

Acetaminophen metabolism that leads to liver failure

A

Oxidation by Cytochrome P450 CYP2E1 to NAPQI

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34
Q

NAPQI detoxification mechanism

A

Sulfhydryl donated by glutathione

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35
Q

Most common cause of acute liver failure

A

Acetaminophen-induced hepatotoxicity (>15 g)

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36
Q

Factors contributing to acetaminophen toxicity

A

Induction of P450 (alcohol, barbiturates) and depletion of glutathione (fasting)

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37
Q

Acetaminophen hepatotoxicity treatment

A

N-acetylcysteine (glutathione precursor), ideally within 8 hours of ingestion or as long as 24-36 hours

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38
Q

Coombs-negative hemolytic anemia with jaundice, low ceruplasmin, high urinary copper

A

Wilson’s disease

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39
Q

Kayser-Fleischer rings

A

Wilson’s disease

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40
Q

Wilson’s disease- presentation

A

Coombs-negative hemolytic anemia with jaundice, low serum ceruplasmin, high urinary copper, Kayser-Fleischer rings

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41
Q

Signs of poor survival in hepatitis A

A

Serum creatinine >2, need for blood pressure support/intubation

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42
Q

Acute fatty liver of pregnancy (HELLP)- presentation

A

Triad of jaundice, coagulopathy, and low platelets during the last trimester. Features of pre-eclampsia common.

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43
Q

Treatment for mushroom toxicity

A

Penicillin G and Silymarin

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44
Q

Liver failure- ammonia metabolism

A

Muscles and urease-splitting bacteria in the gut create ammonia. Normally, the liver converts ammonia to urea, but in liver failure this does not occur properly. Excess ammonia is converted to glutamine in muscle and brain (astrocytes). Causes cerebral edema.

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45
Q

When is lactulose effective in hepatic encephalopathy?

A

If it results from chronic liver disease. May worsen hyponatremia and acidosis.

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46
Q

Goal intracranial pressure in hepatic encephalopathy

A

<20 mmHg

47
Q

Management of increased intracranial pressure

A

head elevation, hyperventilation, mannitol, hypothermia, pentobarbitol

48
Q

Leading cause of death in liver failure

A

Sepsis (70% gram-positive => 35% Staph aureus)

49
Q

Hemochromatosis- inheritance

A

Autosomal recessive mutation of the HFE gene (chromosome 6)

50
Q

Hemochromatosis- pathophysiology

A

HFE involved in iron absorption. Hemosiderin deposition in liver, pancreas, and heart.

51
Q

Hemochromatosis- histology

A

Micronodular cirrhosis; Prussian blue shows iron deposits; fibrous bridging around regeneration nodules

52
Q

Hemochromatosis- presentation

A

Hepatomegaly, abdominal pain, skin pigmentation, diabetes

53
Q

Wilson’s disease- inheritance

A

Autosomal recessive mutation of ATP7B

54
Q

Wilson’s disease- pathophysiology

A

ATP7B is a transmembrane copper-transporting ATPase, which incorporates copper into ceruplasmin for transport to the liver. Copper from diet builds up in organs, namely the brain, liver, and eyes.

55
Q

Wilson’s disease- histology

A

Steatosis, cirrhosis. Rhodamine stain for copper.

56
Q

Wilson’s disease- treatment

A

Avoiding high-copper foods (e.g. mushrooms, fish) and taking copper chelators (e.g. penicillamine)

57
Q

Alpha-1 trypsin deficiency- presentation

A

Neonatal hepatitis (10%), cirrhosis in adolescence or later, increased risk for hepatocellular carcinoma. Emphysema.

58
Q

Alpha-1 trypsin deficiency- inheritance

A

Autosomal recessive inheritance of Protease inhibitor Z (PiZ) mutation

59
Q

Alpha-1 trypsin deficiency- histology

A

Globular inclusions in hepatocyte cytoplasm on PAS stain, neonatal hepatitis with cholestasis. Cirrhosis in later stages.

60
Q

Acute fatty liver of pregnancy- histology

A

Microvesicular steatosis. Oil-Red-O stain may highlight fat.

61
Q

Acute fatty liver of pregnancy- inheritance pattern

A

Autosomal recessive mutation from mother and father of fetus, affecting the mother.

62
Q

Autosomal dominant polycystic kidney disease- inheritance

A

Effectively autosomal dominant mutation of polycystin-1, a transmembrane glycoprotein. It is initially autosomal recessive, but second copy is mutated later in life. Ciliopathy.

63
Q

Familial hypercholesterolemia- inheritance

A

Incomplete dominance. Mutation in LDL receptor.

64
Q

Serum-sickness like syndrome cause

A

Hepatitis B (10-20%), likely due to circulating immune complexes

65
Q

Alcohol consumption in non-alcoholic fatty liver disease

A

<20 g EtOH per week

66
Q

Most common benign liver tumor

A

Venous malformation (not even a tumor!)

67
Q

Venous malformation- typical location

A

Subcapsular in the posterior right lobe (generally)

68
Q

Venous malformation- diagnosis

A

Ultrasound. Peripheral nodular enhancement; gradually fills with time

69
Q

Focal nodular hyperplasia- presentation

A

Young to middle-age adults, often females. More common in right lobe. Usually asymptomatic, but may have vague abdominal pain. Normal LFTs. Circumscribed lesion with central scar. No capsule. May be associated with brain tumors, pediatric malignancies, and vascular abnormalities.

70
Q

Focal nodular hyperplasia- etiology

A

Hyperplastic response to local vascular abnormality

71
Q

Lifecycle of infantile hemangiomas

A

Grow for 18 months, plateau, then involute

72
Q

Infantile hepatic hemangioma- presentation

A

Usually asymptomatic. Often associated with cutaneous hemangiomas. If big, you may see hepatomegaly, consuptive coagulopathy, jaundice, bleeding, abdominal compartment syndrome, and severe hypothyroidism. Lesions bright on outside and dark (blood) inside on imaging. May be focal, multifocal, or diffuse.

73
Q

Mechanism of hypothyroidism in infantile haptic hemangioma

A

Triidothyronine production by endothelial cells

74
Q

Infantile hepatic hemangioma- histology and stain

A

Back-to-back capillaries with plump endothelial cells. Stains positive for GLUT-1, distinguishing it from congenital hepatic hemangioma.

75
Q

Congenital hepatic hemangioma- histology

A

Dilated, malformed vessels. Lobules of small capillaries. Extramedullary hematopoiesis. Eosinophilic globules.

76
Q

Hepatocellular adenomas- presentation

A

Most common in females in 3rd or 4th decade. Sometimes males with anabolic steroid use or glycogen storage disease. RUQ pain or asymptomatic. Usually in the right lobe. Labs may show chronic anemia, elevated CRP, elevated LFTs. Associated with oral contraceptives, FAP, oxicarbazine (sz) and DM.

77
Q

Hepatocellular adenomas- subclassification

A

1) HNF1 mutation- adenomatosis, fatty. Associated with MODY.
2) Beta-catenin- malignant transformation possible. Pleiomorphism. Associated with FAP.
3) Inflammation- associated with elevated CRP, dilated sinusoids, foci of inflammation. Activation mutation of gp130 (co-receptor for IL-6 that activates JAK-STAT)
4) Non-inflammatory

78
Q

PNPLA3 genotype association

A

Non-alcoholic fatty liver disease

79
Q

Chickenwire fibrosis

A

NASH, often in zone 3, starting near the terminal hepatic venule of the lobule

80
Q

Non-alcoholic fatty liver disease- lab findings

A

serum transaminases elevated, ALT > AST, elevated ALP, elevated serum ferritin

81
Q

Antivirals against Hep B and HIV

A

Lamivudine (NRTI), Emtricitabine (NRTI) tenofavir (NtRTI)

82
Q

Viral hepatitis with direct cytopathic effects

A

Hepatitis D

83
Q

NS5B inhibitors for Hep C

A

Hep C RNA-dependent RNA polymerase

84
Q

NS5A inhibitors for Hep C

A

Hep C phosphoprotein

85
Q

NS3

A

Hep C protease, helicase, NTPase

86
Q

NS4A

A

Hep C cofactor for NS3 (function of NS4B is unknown)

87
Q

-asvir in Hep C treatment (Ledipasvir, Ombitasvir, Daclatasvir, Elbasvir)

A

NS5A inhibitors; “-A5vir”

88
Q

-buvir in Hep C treatment (sofosbuvir, dasabuvir)

A

NS5B inhibitors; “Buvir”

89
Q

-previr in Hep C treatment (Paritaprevir, Grazoprevir)

A

NS3/NS4 inhibitors; pr => protease

90
Q

Pre-exposure prophylaxis for HIV (PrEP)

A

Truvada: emtricitabine + tenofavir

91
Q

Truvada efficacy

A

Highest in MSM, followed by MSW. Lowest in heterosexual women.

92
Q

Receptors for HIV

A

CCR5, CXCR4

93
Q

CCR5 antagonist

A

Maraviroc

94
Q

HIV fusion inhibitor

A

Enfuviritide (rarely used)

95
Q

Nucleoside Reverse Transcriptase Inhibitors (NRTIs)- MOA and examples

A

Chain terminators that lack 3’ hydroxyl group. E.g. AZT and Lamivudine

96
Q

Non-nucleoside Reverse Transcriptase Inhibitors (NNRTIs)

A

Binds to reverse transcriptase to antagonize directly

97
Q

Efavirenz- MOA; HIV; characteristics

A

NNRTI; HIV; CNS penetration causes vivid dreams

98
Q

Rilpivirine- MOA, uses, characteristics

A

NNRTI; HIV; avoid antacids

99
Q

Etravirine- MOA, uses, characteristics

A

NNRTI; HIV; CYP450 inhibitor and inducer

100
Q

Zidovudine (AZT)- MOA, uses, ADRs

A

NRTI; children born to HIV+ mothers; macrocytic anemia

101
Q

Abacavir- MOA, uses, ADRs

A

NRTI; HIV but NOT hep B; hypersensitivity in HLA-B7*01

102
Q

Tenofovir- MOA, uses, ADRs

A

NRTI; HIV; decreased bone density, Fanconi syndrome

103
Q

-tegravir in HIV

A

Integrase inhibitors (INSTI)

104
Q

Raltegravir- MOA, uses, characteristics

A

INSTI; HIV; Steven-Johnson syndrome, myopathy

105
Q

Dolutegravir- MOA, uses, characeristics

A

INSTI; HIV; Metformin interaction

106
Q

Ritonavir- MOA, uses, characteristics

A

Protease inhibitor; HIV; used as booster because it caused GI side effects at therapeutic dose

107
Q

Darunavir- MOA, uses, characteristics

A

Protease inhibitor; HIV; contains sulfa moiety but generally tolerated

108
Q

-navir in HIV

A

Protease inhibitors

109
Q

-viren(-) in HIV

A

NNRTI

110
Q

Combo found in all HIV cocktails

A

2 NRTIs

111
Q

CD4 count for pneumocystis, esophageal candidiasis

A

200

112
Q

CD4 count for cryptococcus, toxoplasmosis

A

100

113
Q

CD4 count for Mycobacteriumavium

A

50

USMLE STEP 1 (24 decks)

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