What Is Gallstones: Formation, Symptoms, and When Surgery Is Needed

This article is for informational purposes only. Consult a qualified healthcare professional for medical advice, diagnosis, or treatment.

What Are Gallstones?

Gallstones (cholelithiasis) are solid deposits that form within the gallbladder — a small, pear-shaped organ located beneath the liver on the right side of the abdomen. The gallbladder stores and concentrates bile, a digestive fluid produced by the liver that emulsifies dietary fats. Gallstones develop when the components of bile precipitate out of solution and crystallize. Gallstones affect approximately 10–15% of adults in Western countries — an estimated 20 million Americans have gallstones, though most never experience symptoms. Worldwide, cholelithiasis is one of the most common gastrointestinal conditions requiring hospital admission. In the United States alone, approximately 750,000 cholecystectomies (gallbladder removal surgeries) are performed annually.

Types of Gallstones

Type	Composition	Prevalence	Risk Factors
Cholesterol gallstones	≥80% cholesterol monohydrate crystals	~75–80% of gallstones in developed countries	Obesity, rapid weight loss, female sex, multiparity, oral contraceptives, age >40, native American/Hispanic ethnicity
Black pigment stones	Calcium bilirubinate, calcium phosphate; small, hard, irregular	~15–20%	Hemolytic anemia (sickle cell, hereditary spherocytosis, thalassemia), liver cirrhosis, old age
Brown pigment stones	Calcium bilirubinate, calcium palmitate; softer, earthy	~5%; more common in Asia	Biliary tract infection, bile stasis, foreign bodies (parasites, sutures)

How Cholesterol Gallstones Form

Cholesterol is insoluble in water and is maintained in solution in bile through its association with bile salts (detergents) and phospholipids (predominantly lecithin) in mixed micelles. The balance between these components is critical. Three conditions promote cholesterol crystallization and stone formation:

Cholesterol supersaturation: When cholesterol is secreted into bile in excess relative to bile salts and phospholipids, bile becomes lithogenic (stone-forming). The liver may hypersecrete cholesterol (as in obesity) or under-secrete bile salts (as after ileal resection, which reduces enterohepatic bile salt recirculation).
Nucleation: Supersaturated cholesterol precipitates as solid crystals. Pro-nucleating factors (mucin glycoproteins, immunoglobulins) in bile accelerate crystal formation; anti-nucleating factors (apolipoproteins A-I and A-II) normally inhibit this process.
Gallbladder stasis: Reduced gallbladder motility allows crystals time to aggregate and grow into macroscopic stones. Conditions causing stasis include prolonged fasting, parenteral nutrition, pregnancy, and diabetes.

Risk Factors: The "Five F's" and Beyond

The classic mnemonic for cholesterol gallstone risk factors is the "Five F's":

Fat (obesity): BMI >30 increases risk 2–3 fold; visceral adiposity increases hepatic cholesterol secretion
Forty (age >40): Bile becomes increasingly lithogenic with age
Female: Estrogen increases hepatic cholesterol secretion and reduces gallbladder motility; women are 2× more likely to develop gallstones
Fertile (pregnancy): Elevated progesterone reduces gallbladder motility; gallstone formation doubles in pregnancy
Family history: First-degree relatives of gallstone patients have 2× higher risk; genetic variants in cholesterol transport genes (ABCG5/G8) strongly influence lithogenicity

Additional risk factors include rapid weight loss (mobilizes cholesterol into bile faster than bile salt synthesis can compensate), prolonged fasting, total parenteral nutrition, Crohn's disease (terminal ileal inflammation/resection impairs bile salt reabsorption), and certain medications (fibrates, octreotide, thiazides).

Clinical Presentation

Asymptomatic Gallstones

Approximately 75–80% of people with gallstones are asymptomatic ("silent stones"). Asymptomatic gallstones become symptomatic at a rate of approximately 1–2% per year. Most guidelines do not recommend prophylactic cholecystectomy for truly asymptomatic stones, except in specific high-risk groups (porcelain gallbladder — though evidence is debated — and patients with sickle cell disease).

Biliary Colic

The characteristic symptom of symptomatic gallstones is biliary colic: episodic, severe right upper quadrant or epigastric pain that builds steadily over 15–60 minutes to a constant (not truly "colicky") plateau, lasts 1–5 hours, then gradually resolves. It typically occurs 1–3 hours after a fatty meal (when gallbladder contraction forces a stone against the cystic duct outlet). Associated nausea and vomiting are common. Between episodes, the patient is well. Recurrence after a first attack is ~70% within 2 years without treatment.

Complications

Complication	Mechanism	Key Symptoms
Acute cholecystitis	Cystic duct obstruction causes gallbladder distension, wall ischemia, and bacterial superinfection	Persistent RUQ pain (>6 hours), fever, positive Murphy's sign, elevated WBC
Choledocholithiasis	Stone migrates to common bile duct, causing obstruction	Jaundice, dark urine, pale stools, elevated bilirubin and ALP; ± pain
Acute cholangitis	Choledocholithiasis + biliary tract infection; can be life-threatening (Charcot's triad: fever, jaundice, RUQ pain)	Fever, jaundice, pain (Charcot's triad); septic shock in severe cases (Reynolds' pentad)
Acute pancreatitis	Gallstone impacting ampulla of Vater blocks pancreatic duct drainage	Severe epigastric pain radiating to the back, elevated amylase/lipase; 30–50% of acute pancreatitis cases in developed countries
Gallstone ileus	Large stone erodes through gallbladder wall into intestine; causes mechanical bowel obstruction	Signs of small bowel obstruction; air in biliary tree on imaging

Diagnosis

Abdominal ultrasound is the investigation of choice for suspected gallstones. It has sensitivity >95% and specificity >95% for gallbladder stones, is inexpensive, readily available, and involves no radiation. Ultrasound findings include hyperechoic foci with posterior acoustic shadowing that move with patient positioning. For suspected choledocholithiasis or biliary complications, magnetic resonance cholangiopancreatography (MRCP) provides excellent visualization of the biliary tree without contrast or radiation. CT imaging is useful for detecting complications like perforation or abscess but is less sensitive for detecting small gallstones.

When Is Surgery Needed?

Laparoscopic cholecystectomy — the keyhole surgical removal of the gallbladder — is the definitive treatment for symptomatic gallstones. It is one of the most commonly performed surgical procedures in the world. Indications include:

Symptomatic gallstones with recurrent biliary colic
Acute cholecystitis (ideally within 72 hours of diagnosis — early surgery is superior to delayed in multiple trials)
Choledocholithiasis (usually after ERCP stone clearance)
Gallstone pancreatitis (cholecystectomy during the same admission after resolution prevents recurrence)

The gallbladder is not essential for digestion; after removal, bile drains continuously from the liver into the small intestine. Some patients experience post-cholecystectomy diarrhea or fatty food intolerance, which typically resolves within weeks to months. Non-surgical options (ursodeoxycholic acid to dissolve cholesterol stones) exist but require months to years of treatment and are rarely curative in isolation.