Icterus: The Major Causes of Jaundice

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  • 0:36 What Is Bile and Bilirubin?
  • 2:26 What Is Icterus and Jaundice?
  • 2:54 Unconjugated…
  • 4:35 Conjugated Hyperbilirubinemia
  • 5:27 The Role of Urine and Stool
  • 6:12 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov
This lesson will discuss the major causes of icterus, also known as jaundice. We'll define conjugated and unconjugated bilirubin, when each one may increase, how urine and stool samples may be important, and a whole lot more!

A Delicious and Important Organ

No matter how you slice it, whether for dinner or for investigation under the microscope, the liver is a very important, and to some, even delicious, organ.

It produces important proteins, such as albumin, which ensures you don't look swollen, and allows for the transport of important drugs. It helps to detoxify things that may be dangerous to your health. It also helps to give you energy by generating glucose, and so much more!

As you can tell, the liver is a powerhouse of an organ. It's also a key player in this lesson's foray into a colorful, but very serious, sign some sick people get.

What Is Bile and Bilirubin?

Other than all of the things that I just mentioned the liver is important for, it's also important for the production of something known as bile. This is a greenish liquid produced in the liver and stored in the gallbladder, which facilitates the digestion of fat.

Bile, among other things, contains something known as bilirubin. Bilirubin is an orange-yellow pigment formed from the breakdown of red blood cells. Bilirubin is converted into other substances that eventually give urine its yellow color and feces its yellow-brown color. Who knew physiology could be so colorful and yet so disgusting?

When red blood cells break down due to age or destruction, then something known as unconjugated or indirect or water-insoluble bilirubin is released into the bloodstream. Once this unconjugated bilirubin enters the liver, the liver converts it into conjugated or direct or water-soluble bilirubin by tacking on a compound known as glucuronic acid; this is what makes bilirubin water soluble.

This newly water-soluble bilirubin is then secreted into the watery bile and, from there, into the intestines.

If all of this is making your head spin, don't worry; we can simplify it even more. Your liver is like a giant factory. Through one end, raw ingredients come in by the truckload. In our case, that's crates and crates of raw, hard, and unprocessed indirect bilirubin. Once inside the factory, the workers take a piece of unconjugated bilirubin and stick another ingredient right onto it, thereby making an entirely new concoction, called conjugated bilirubin. This conjugated bilirubin isn't hard like unconjugated bilirubin; it's slushy and can dissolve easily in water instead.

What Is Icterus and Jaundice?

If the levels of either the conjugated or unconjugated bilirubin increase in the body, they can cause icterus, which is the more technical term for jaundice. If you are not sure of what jaundice is, then let me explain. Jaundice is the yellowing of the whites of the eyes, mucous membranes, and a person's skin as a result of abnormally increased levels of bilirubin in the blood, aka hyperbilirubinemia.

What Causes Unconjugated Hyperbilirubinemia?

Based on what I've said thus far, you should be aware that the ways by which levels of unconjugated bilirubin can increase are:

  1. if something causes indirect bilirubin levels to rise before they reach the liver
  2. if unconjugated bilirubin isn't being delivered properly to the liver (both of which are also known as pre-hepatic causes)
  3. if there's something wrong with the liver that disables the conversion mechanism to conjugated bilirubin (also known as hepatic causes)

So, in simple terms, that means the raw ingredients either aren't delivered to the factory or the factory has broken down.

Therefore, any cause of hemolytic anemia, where red blood cells are destroyed due to things like pathogens, drugs, autoimmune disease, or physical damage, will release tons of unconjugated bilirubin into circulation. Since there is so much being released into circulation, the liver is simply overwhelmed and cannot conjugate enough of the bilirubin fast enough. This is like our factory workers getting a ton of crates delivered to them, but without an increase in the amount of workers, the crates just keep piling up and up without being processed.

If the liver is unable to take up enough indirect bilirubin due to poor circulation, as with congestive heart failure or a portosystemic shunt, then it can't conjugate enough of it.

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