How are gallstones formed?
In this blog post, we shall learn about How are gallstones formed. Gallstones are hard, pebble-like pieces of material, usually made of cholesterol or bilirubin, that develop in the gallbladder. When gallstones block the bile ducts, they can cause sudden pain, which means you need immediate medical attention. If left untreated, they can cause complications.
There are two types of gallstones:
- Cholesterol stones
- Pigment stones.
If you knew nothing about gallstones, you would (rightly) assume that cholesterol stones are made of cholesterol. And you probably also guess that you get cholesterol stones when there’s too much cholesterol around. But how, exactly? And pigment stones, what are they made of? Pigment?
Cholesterol gallstones contain, unsurprisingly, cholesterol. And they arise when there is more cholesterol than the gallbladder can handle. But what does this really mean?
A little basic science here. Under normal conditions, cholesterol is soluble in bile because it binds to bile salts (which are soluble in water) and lecithins (which are insoluble in water). Both types act as detergents, and the cholesterol is dispersed within the bile, and all is well.
But what happens if there is too much cholesterol around? If the cholesterol concentration exceeds the bile solubilizing capacity, then the cholesterol will nucleate into solid cholesterol crystals, which over time can grow large enough to form stones.
Signs and Symptoms of Gallstones
- Pain in your upper belly, often on the right, just under your ribs
- An upset stomach
- Pain in your right shoulder or back
- Other digestive problems, including indigestion, heartburn, and gas
Visit your doctor or the hospital if you have signs of a serious infection or inflammation:
- Belly pain that lasts several hours
- Fever and chills
- Yellow skin or eyes
- Dark urine and light-colored poop
These stones are made of unconjugated bilirubin (mixed with calcium salts). They are called pigment gallstones because they are dark brown to black in color (compared to cholesterol stones, which are usually pale greenish-yellow).
The two main conditions in which pigment stones are seen are chronic hemolytic anemia and biliary tract infection. Why would these conditions lead to an accumulation of unconjugated bilirubin in the bile? To answer that, let’s quickly review the metabolism of bilirubin in bile itself.
Normally, the liver conjugates bilirubin and releases it into bile. So bile contains only conjugated bilirubin, so right? Wrong! About 1% of the bilirubin in bile deconjugates while still in the biliary tree (I bet you didn’t know that!). The bile then empties into the intestine, where bacterial β-glucuronidases convert most of the remaining conjugated bilirubin to its unconjugated form.
Let’s go back to the causes of pigmented stones. If you have an infection in the biliary tree and the infectious agent produces Î²-glucuronidase, you will end up deconjugating more bilirubin than normal… and over time, that unconjugated bilirubin can build up and form stones.
The other main cause of pigmented stones is chronic hemolysis. If you break up too many red blood cells, all that heme turns into bilirubin, which the liver conjugates and releases into bile. So the bile contains much more bilirubin than usual. Most of that bilirubin remains conjugated, but about 1% is converted to unconjugated bilirubin right there in the biliary tree. If you are making much more bilirubin than normal, that 1% is significant, and over time that excess unconjugated bilirubin may be enough to cause pigment stone formation.