Jaundice: Causes and Metabolism

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Questions and Answers

What is the earliest sign of jaundice?

  • Dark urine
  • Increased abdominal pain
  • Yellow discoloration of the skin
  • Yellow discoloration of the sclera (correct)

Which condition is characterized by high levels of unconjugated bilirubin (UCB) overwhelming the liver's conjugating ability?

  • Extravascular hemolysis (correct)
  • Dubin-Johnson syndrome
  • Crigler-Najjar syndrome
  • Gilbert syndrome

In which type of jaundice does phototherapy serve as an effective treatment?

  • Physiologic jaundice of the newborn (correct)
  • Gilbert syndrome
  • Crigler-Najjar syndrome
  • Dubin-Johnson syndrome

What is the cause of kernicterus in physiologic jaundice of the newborn?

<p>Low UGT activity (C)</p> Signup and view all the answers

Which syndrome presents with a deficiency of the bilirubin canalicular transport protein?

<p>Dubin-Johnson syndrome (B)</p> Signup and view all the answers

What is a common clinical feature observed in Gilbert syndrome?

<p>Jaundice during stress or infection (D)</p> Signup and view all the answers

What distinguishes Crigler-Najjar syndrome from other forms of jaundice?

<p>It results from an absence of uridine glucuronyl transferase. (D)</p> Signup and view all the answers

Which of the following accurately describes a consequence of increased unconjugated bilirubin (UCB) in the blood?

<p>Yellow discoloration of skin and sclera (D)</p> Signup and view all the answers

Flashcards

Jaundice

Yellow discoloration of the skin, most often due to increased bilirubin levels in the blood. It usually signifies a problem with the liver's ability to process bilirubin.

Bilirubin Metabolism: Step 1

The breakdown of heme from red blood cells into unconjugated bilirubin (UCB), which then has to be processed by the liver.

Bilirubin Metabolism: Step 2

Unconjugated bilirubin (UCB) is transported by albumin to the liver, where it's processed further.

Bilirubin Metabolism: Step 3

Enzymes within hepatocytes convert unconjugated bilirubin (UCB) into a water-soluble form called conjugated bilirubin (CB).

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Bilirubin Metabolism: Step 4

Conjugated bilirubin (CB) is excreted through the bile ducts into the small intestine.

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Bilirubin Metabolism: Step 5

Intestinal bacteria convert conjugated bilirubin (CB) into urobilinogen. Some urobilinogen is reabsorbed into the blood, giving urine its yellow color, while the rest is excreted in feces, making them brown.

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Unconjugated Hyperbilirubinemia

A condition where the liver has trouble conjugating and excreting bilirubin, resulting in high unconjugated bilirubin levels.

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Conjugated Hyperbilirubinemia

A condition characterized by high levels of conjugated bilirubin in the blood, often due to problems with bile flow or liver cell function.

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Study Notes

Jaundice

  • Yellow discoloration of skin and sclera, caused by elevated serum bilirubin (usually > 2.5 mg/dL) This is the earliest sign
  • Result of disturbances in bilirubin metabolism.

Normal Bilirubin Metabolism

  • Breakdown of red blood cells (RBCs) by macrophages in the reticuloendothelial system.
  • Conversion of protoporphyrin from heme to unconjugated bilirubin (UCB).
  • Transport of UCB to the liver via albumin.
  • Conjugation of bilirubin by uridine glucuronyl transferase (UGT) in hepatocytes to form conjugated bilirubin (CB).
  • Transfer of CB to bile canaliculi and formation of bile, stored in the gallbladder.
  • Release of bile into small intestine for digestion and absorption.
  • Conversion of CB to urobilinogen by intestinal flora, then to stercobilin (for brown feces) and urobilin (for yellow urine).

Clinical features and Laboratory findings in Jaundice

  • Extravascular hemolysis or Ineffective erythropoiesis: High UCB levels overwhelm the liver's ability to conjugate it resulting in dark urine due to increased urine urobilinogen . Risk of pigmented bilirubin gallstones.
  • Physiological jaundice of the newborn: Transiently low UGT activity in newborns, resulting in increased UCB. Increased risk of kernicterus (brain damage) if untreated.
  • Gilbert syndrome: Mildly low UGT activity; autosomal recessive, increased UCB.
  • Crigler-Najjar syndrome: Absence of UGT; autosomal recessive, increased UCB, kernicterus usually fatal.
  • Dubin-Johnson syndrome: Deficiency of bilirubin canalicular transport protein, autosomal recessive. Increased CB, decrease urine urobilinogen. Usually not clinically significant unless the liver is dark/brown.
  • Rotor syndrome: Similar to Dubin-Johnson, but without liver discoloration. Increased bilirubin in blood.
  • Biliary tract obstruction: Associated with gallstones, pancreatic carcinoma, cholangiocarcinoma, parasites, liver fluke. Increased CB, decreased urine urobilinogen, and increased alkaline phosphatase.
  • Viral hepatitis: Inflammation disrupts hepatocytes; Increased CB, and UCB.

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