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VET433: Gastroenterology > Icterus > Flashcards

Icterus Flashcards

1
Q

hyperbilirubinemia

A

elevated serum or plasma bilirubin

does NOT always cause icterus

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2
Q

normal bilirubin concentration

A

<0.2 mg/dL

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3
Q

at what concentration is bilirubin detectable in plasma (icteric plasma)

A

> 0.5 mg/dL

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4
Q

at what concentration is bilirubin detectable in tissues (icterus)

A

> 2.0 mg/dL

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5
Q

icterus

A

yellowing of plasma caused by hyperbilirubinemia

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6
Q

bilirubinuria

A

bilirubin in the urine

ALWAYS pathologic in cats
can be normal in dogs

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7
Q

cholestasis

A

decrease in bile flow

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8
Q

intrahepatic cholestasis

A

slow, congested liver causing impaired bile flow

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9
Q

extrahepatic cholestasis

A

biliary system obstruction

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10
Q

bile

A

water + bile acids + bile salts + bilirubin + cholesterol + FAs + lecithin + electrolytes + bicarbonate

continuously produced by the LIVER and released into duodenum OR stored and concentrated in the gallbladder

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11
Q

what are the functions of bile

A
  1. fat emulsification and digestion
  2. excretion of waste (bilirubin, cholesterol, drugs, toxins)
  3. bactericidal (maintains intestinal pH to prevent dysbiosis)
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12
Q

steps of bilirubin metabolism

A

physiologic extravascular hemolysis:
1. RBC breaks down into heme and globin
2. heme enters the spleen and gets taken up by splenic macrophages
3. heme –> biliverdin
4. biliverdin –> unconjugated bilirubin
5. UC bilirubin (lipid soluble) binds albumin to travel to liver
6. UC bilirubin –> C bilirubin in the liver
7. C bilirubin (water soluble) gets released into bile
8. bile –> intestines –> deconjugation by microbes to form urobilinogen + stercobilin
9. stercobilin released in feces; urobilinogen travels to kidneys OR enterohepatic circulation back to the liver
10. urobilinogen –> urobilin in kidneys –> released in urine

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13
Q

what are the three mechanisms of icterus

A
  1. prehepatic
  2. hepatic
  3. posthepatic
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14
Q

prehepatic icterus

A

hemolytic anemia

PATHOLOGIC extravascular hemolysis –> exceeds normal bilirubin levels –> hyperbilirubinemia

elevated UNCONJUGATED bilirubin

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15
Q

hepatic icterus

A

primary liver dysfunction caused by:
1. decreased functional liver mass
2. functional cholestasis (intrahepatic)

elevated UNCONJUGATED or CONJUGATED bilirubin

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16
Q

posthepatic icterus

A

biliary system dysfunction caused by:
1. extrahepatic bile duct obstruction (EHBDO)
2. gallbladder rupture

elevated CONJUGATED bilirubin

17
Q

clinical signs associated with icteric patients

A

icterus - sclera, pinnae, MM
weight loss
inappetance
vomiting
diarrhea

+/- abdominal pain (EHBDO), hepatomegaly, effusion

18
Q

differentials for prehepatic icterus

A

hemolytic anemia
1. IMHA
2. heinz body anemia (oxidative damage - zinc, onion, acetaminophen tox)
3. infectious (mycoplasma, babesia)
4. transfusion reaction
5. microangiopathic (DIC, splenic HSA, heartworm)
6. severe hypophosphatemia

19
Q

differentials for hepatic icterus

A

liver disease

cats:
1. hepatic lipidosis
2. cholangitis
3. FIP

dogs:
1. chronic hepatitis - immune vs copper associated
2. cholangiohepatitis
3. cirrhosis

both:
1. neoplasia - lymphoma
2. acute or chronic toxins
3. bacteremia –> cholestasis of sepsis

20
Q

differentials for posthepatic icterus

A
  1. obstruction
    - pancreatitis
    - GB mucocele
    - cholecystitis
    - neoplasia
    - choledocolith
    - CBD or major duodenal papilla stricture
  2. GB or bile duct rupture
21
Q

what lab values are consistent across all mechanisms of icterus

A

hyperbilirubinemia
icteric plasma
+/- bilirubinuria

22
Q

prehepatic icterus lab values

A

CBC: regenerative anemia w/ normal protein
- morphology: spherocytes, heinz bodies, schistocytes

chem: reactive hepatopathy

23
Q

hepatic icterus lab values

A

CBC: mild NNN anemia +/- leukogram changes

Chem:
- hypoalbuminemia
- HYPOCHOLESTEROLEMIA
- low BUN and glucose

liver enzymes will be more elevated in DOGS than cats due to longer half lives and greater total number of enzymes

UA: isosthenuria from medullary washout (low BUN)

24
Q

posthepatic lab values

A

Chem:
- marked HYPERCHOLESTEROLEMIA
- +/- elevated liver enzymes

25
Q

what is the most important diagnostic for differentiating hepatic from posthepatic icterus

A

ultrasound

  • hepatomegaly –> acute liver disease vs neoplasia
  • microhepatica –> chronic liver disease vs shunt
  • GB/biliary distension –> EHBDO

r/o pancreatitis, mucocele, masses, choleliths, choledocoliths, strictures

26
Q

what additional diagnostics are useful in icteric patients

A
  1. ammonia –> r/o hepatic encephalopathy
  2. coag panel –> r/o liver dysfunction
  3. liver FNA and biopsy –> r/o differentials for liver disease
  4. thoracic radiographs –> if suspected neoplasia
  5. CT scan –> EHBDO, PSS, surgical planning

bile acids are generally NOT indicated with hyperbilirubinemia

27
Q

treating prehepatic icterus

A

treat underlying cause of hemolysis

28
Q

treating hepatic icterus

A

treat underlying hepatopathy

29
Q

treating posthepatic icterus

A

surgical:
- mature mucoceles
- severe cholecystitis
- GB rupture
- masses
- severe pancreatitis

medical:
- pancreatitis
- mild cholecystitis
- immature mucocele

VET433: Gastroenterology (16 decks)

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