Epidemiology

95% of the gallbladder diseases are cholelithiasis (gallstones.)

About 2% of the US health budget goes towards the management of cholelithiasis and its complications.

10%-20% of the population in the western hemisphere has gallstones.
25-50 tons of the gallstones are carried by more than 20 million Americans.

In the US about 1 million new cases are diagnosed annually, out of these, 2/3 will undergo surgery for the gallstones.

Gallstones are of two main types. 80% are cholesterol stones. Consisting of crystalline cholesterol monohydrate. The remainder are mainly bilirubin calcium salts and are called pigment stones.

High-Level Pathophysiology

The basic reason for the formation of the cholesterol stones is the following:
They only path for the cholesterol removal from the body is via the bile system. Cholesterol is not water soluble. We need to make it water soluble to traverse this path. To solve this, our body forms bile salts and lecithins. These bind with cholesterol and allow the passage through the bile system. These salts and lecithins are like boats on the water to which cholesterol is bound. If the quantity of the cholesterol is more than the binding capacity of these salts, then the unbound cholesterol forms cholesterol monohydrate crystals. These crystals precipitate in solid form. These precipitations irritate the gallbladder layers that in turn release mucus which traps these solid structures in the gallbladder resulting in the stone formation.
In summary, the following four events occur simultaneously for the formation of a gallstone:
1. Amount of cholesterol more than the binding capacity of the bile salts (supersaturation.)
2. Formation of the cholesterol monohydrate crystals.
3. Precipitation and aggregation of these crystals forming solid stone particles.
4. Mucus secretion by the gallbladder's inner surface resulting in the entrapment of these solid particles in the gallbladder.

Pigment Stones 

These stones are predominantly composed of bilirubin calcium salts. Their formation is a complex phenomenon. However, it is clear that the presence of unconjugated bilirubin in the bile tree predisposes to the formation of the pigment stones. An example is hemolytic anemia, where the premature RBC breakdown overwhelms the hepatocyte's bilirubin conjugation capacity and the unconjugated bilirubin appears in blood plasma and bile. Infections of the biliary tree can also result in unconjugated bilirubin in the bile.

Also, note that the prevalence of the gallstones is age and gender-related.
Age
Population < 40 has 5% to 6% prevalence of the gallstones.
Population > 80 y has 25% to 30% prevalence of the gallstones.

Gender
Prevalence in white women is twice as high as in men.

Ethnic and geographic
The native American population has a 75% prevalence of cholesterol gallstones. Pigment stones are rare in this group.
Gallstones are more prevalent in western industrialized societies compared to the developing countries.

Robins 8th Edition Page 667

https://www.aafp.org/afp/2004/0115/p299.html

http://eclinpath.com/hematology/anemia/mechanisms-of-anemia/extravascular-hemolysis-new/

Cholelithiasis (Gallstones). Clinical Features.

Frequently cholelithiasis is asymptomatic. It is usually discovered during a  radiographic study or during a surgery, or an autopsy.

Clinical features of gallstones occur due to the obstruction and inflammation of the gallbladder by a large stone, or the small stones that move down in the biliary tree and get stuck in it, or due to the irritation and inflammation of the biliary tree.

Pain is usually excruciating (severe). It may be constant or colicky. The pain of acute cholecystitis is in the upper right quadrant can be associated with fever, nausea, and a positive Murphy's sign.  Biliary or episodic gallbladder pain occurs in 10-25% of the patients. Acute cholecystitis occurs in 20% of these symptomatic patients.

Occasionally gallstone ileus or Bouveret or Mirizzi syndrome occurs as a clinical complication of a gallstone. Bouveret syndrome occurs when the stone obstructs pylorus or duodenum.

Murphy's sign is positive when you palpate the upper right quadrant during inspiration, and the patient's breathing is interrupted or stopped due to the pain.

You can also perform an indirect fist percussion to compare any difference in pain in the right upper quadrant and the left upper quadrant.

Robbins 8th Edition: Page 668
Current Medical Diagnosis and Treatment 2016 - Cholelithiasis chapter.
https://www.youtube.com/watch?v=9L7N89sOSuc