Jaundice - causes, treatment & pathology

Summary

This script delves into jaundice, a condition characterized by the yellowing of skin and eyes due to bilirubin accumulation. It explains the process of bilirubin production from red blood cells, its metabolism in the liver, and excretion via bile and urine. The script also covers various causes of jaundice, including increased bilirubin production, liver dysfunction, and genetic disorders, and touches on treatments like phototherapy. It highlights the importance of understanding the bilirubin metabolism pathway for diagnosing and managing jaundice effectively.

Takeaways

• 📘 Jaundice, also known as icterus, is a condition characterized by yellowing of the skin and eyes due to the accumulation of bilirubin.
• 🩸 Bilirubin is a byproduct of hemoglobin breakdown from red blood cells, which have a lifespan of about 120 days.
• 🧬 The reticuloendothelial system, particularly the spleen, plays a key role in breaking down old red blood cells into heme and globin.
• 🧪 Heme is further broken down into iron and protoporphyrin, which is then converted into unconjugated bilirubin (UCB).
• 🚑 UCB is lipid-soluble and bound by albumin in the blood, transported to the liver, and converted into water-soluble conjugated bilirubin (CB) by the enzyme UGT.
• 🌱 CB is secreted into the bile and stored in the gallbladder, then released into the small intestine where it is converted to urobilinogen (UBG) by gut microbes.
• 💩 Stercobilin, derived from UBG, is responsible for the brown color of feces, while some UBG is recycled and contributes to the yellow color of urine.
• 🚨 Disruptions in bilirubin metabolism can lead to jaundice, with symptoms including yellowing of the skin and sclera of the eyes.
• 👶 Physiologic jaundice of newborns is common due to immature liver function and the breakdown of fetal red blood cells, which can be treated with phototherapy.
• 🧬 Genetic disorders such as Gilbert's syndrome and Crigler-Najjar syndrome can affect the liver's ability to process bilirubin, leading to jaundice.
• 🔍 Jaundice can be caused by various factors including increased red blood cell breakdown, liver disease, bile duct obstruction, and viral infections.

Q & A

What is the medical term for the yellowing of the skin and eyes due to a buildup of a certain pigment?

The medical term for the yellowing of the skin and eyes is jaundice, which is caused by a buildup of bilirubin.

What is the origin of the term 'jaundice'?

The term 'jaundice' comes from the French word 'jaunice,' meaning yellowing, and is also sometimes referred to as icterus.

What is bilirubin and why is it significant in the context of jaundice?

Bilirubin is a yellow pigment that is a component of bile. It is significant in jaundice because its buildup in the blood causes the yellowing of the skin and eyes.

Where does bilirubin come from in the body?

Bilirubin comes from the breakdown of hemoglobin in red blood cells by macrophages in the reticuloendothelial system, primarily in the spleen.

What is the role of the liver in the metabolism of bilirubin?

The liver plays a crucial role in the metabolism of bilirubin by taking up unconjugated bilirubin (UCB), conjugating it with an enzyme called uridine glucuronyl transferase (UGT), and making it water-soluble for excretion.

How is bilirubin transported from the liver to the gallbladder and eventually to the small intestine?

Conjugated bilirubin is secreted into the bile canaliculi, drains into the bile ducts, and is stored in the gallbladder. Upon eating, the gallbladder secretes bile containing conjugated bilirubin, which then moves to the duodenum of the small intestine.

What happens to bilirubin in the small intestine and what is urobilinogen?

In the small intestine, intestinal microbes convert conjugated bilirubin to urobilinogen (UBG), which is further reduced to stercobilin, contributing to the brown color of feces, and some of it is recycled back into the blood.

What causes the yellow color in the urine in the context of jaundice?

The yellow color in the urine during jaundice is due to the presence of urobilin, a product of the oxidation of urobilinogen, which is excreted by the kidneys.

What are some conditions that can lead to increased levels of unconjugated bilirubin in the blood?

Conditions that can lead to increased levels of unconjugated bilirubin in the blood include extravascular hemolytic anemias, where red blood cells are broken down prematurely, and ineffective hematopoiesis, where blood cells don't form correctly in the bone marrow.

What is the potential risk of high levels of unconjugated bilirubin in newborns?

High levels of unconjugated bilirubin in newborns can lead to a condition called kernicterus, where bilirubin accumulates in the basal ganglia of the brain, potentially causing brain damage or death.

How is jaundice in newborns typically treated?

Jaundice in newborns is typically treated with phototherapy, which uses light to induce changes in the bilirubin molecule, making it more soluble and easier to excrete in the urine.

What is the difference between Gilbert's syndrome and Crigler-Najjar syndrome in terms of bilirubin metabolism?

Gilbert's syndrome is characterized by low UGT enzyme activity, which can lead to an accumulation of unconjugated bilirubin in the blood under certain conditions. Crigler-Najjar syndrome, on the other hand, is characterized by a near absence of UGT, leading to extremely high levels of unconjugated bilirubin and a high risk of kernicterus.

What is Dubin-Johnson syndrome and how does it relate to jaundice?

Dubin-Johnson syndrome is an autosomal recessive disorder characterized by a deficiency in the MRP2 protein, which helps move conjugated bilirubin from liver cells to bile ducts. This leads to an accumulation of conjugated bilirubin in the liver and its subsequent leakage into the blood, causing jaundice.

What is obstructive jaundice and what causes it?

Obstructive jaundice occurs when there is a blockage in the flow of bile, which can be caused by gallstones, pancreatic carcinomas, cholangiocarcinomas, or parasites like the liver fluke. This blockage leads to an increase in conjugated bilirubin in the blood and other symptoms.

How does viral hepatitis affect bilirubin levels in the blood?

Viral hepatitis can lead to both conjugated and unconjugated bilirubin in the blood. Infected and dying hepatocytes lose the ability to conjugate bilirubin, leading to excess unconjugated bilirubin, and also allow bile to leak into the blood, increasing conjugated bilirubin levels.