Kolelitiasis

01Pathophysiology

Gallstones form when the chemical balance of bile within the gallbladder is disrupted. Bile is composed of cholesterol, bile salts, and phospholipids (mainly lecithin). Under normal conditions, bile salts and lecithin keep cholesterol solubilized in mixed micelles. When cholesterol concentration exceeds the solubilizing capacity of bile salts and lecithin, bile becomes supersaturated, and cholesterol crystals nucleate and grow into stones. This is the mechanism behind cholesterol stones, which account for roughly 80% of gallstones in Western populations.

The classic mnemonic "4 F's" (Fat, Female, Fertile, Forty) captures the key risk factors. Estrogen increases hepatic cholesterol secretion and reduces bile salt synthesis, explaining why women, especially those who are pregnant, taking oral contraceptives, or on hormone replacement therapy, are at higher risk. Obesity increases cholesterol synthesis and secretion into bile, while rapid weight loss (such as after bariatric surgery or very-low-calorie diets) paradoxically increases stone formation because the liver mobilizes cholesterol from peripheral stores faster than bile salts can solubilize it. Gallbladder hypomotility during fasting, prolonged total parenteral nutrition, or pregnancy also promotes stasis and stone formation.

Pigment stones account for the remaining 20% and come in two subtypes. Black pigment stones are composed of calcium bilirubinate and form in conditions of chronic hemolysis (sickle cell disease, hereditary spherocytosis, thalassemia) or cirrhosis, where unconjugated bilirubin is overproduced. These stones form within the gallbladder itself. Brown pigment stones are associated with biliary stasis and infection (particularly with E. coli and biliary parasites) and can form in the bile ducts (primary choledocholithiasis). They are more common in East Asian populations.

The link between pathophysiology and symptoms is direct: stones sitting quietly in the gallbladder cause no symptoms. Pain occurs only when a stone transiently obstructs the cystic duct during gallbladder contraction (stimulated by cholecystokinin release after a fatty meal). The gallbladder contracts against the obstruction, producing visceral pain felt in the epigastrium or RUQ. When the stone falls back into the gallbladder or passes through, the pain resolves. This is why biliary colic is episodic and self-limited (typically < 6 hours). If the stone becomes impacted and does not dislodge, this progresses to acute cholecystitis, a different and more serious diagnosis.

02Classification and Clinical Manifestation

03Diagnostic Workup

The best initial test for cholelithiasis is a right upper quadrant ultrasound. It is also the most accurate test for detecting stones within the gallbladder, with a sensitivity above 95%. The hallmark finding is a hyperechoic focus that casts a posterior acoustic shadow and moves with changes in patient position (demonstrating mobility and distinguishing stones from polyps, which are fixed to the wall). Ultrasound also allows assessment of gallbladder wall thickness, pericholecystic fluid, and common bile duct diameter, which helps determine whether complications are present.

 In uncomplicated cholelithiasis, laboratory tests are expected to be entirely normal. The reason you still order a CBC, liver function panel, and lipase is not to diagnose gallstones but to rule out complications. A normal WBC argues against cholecystitis. Normal bilirubin and alkaline phosphatase argue against a stone in the common bile duct (choledocholithiasis). Normal lipase rules out gallstone pancreatitis. On the exam, when a vignette gives you a patient with biliary colic and completely normal labs, they are confirming uncomplicated cholelithiasis and guiding you toward elective management.

 Plain abdominal X-ray is a poor test for gallstones because the majority (cholesterol stones) are radiolucent. Do not choose X-ray as the initial diagnostic study. The only situation where stones appear on X-ray is when they contain enough calcium (pigment stones) or in the rare "porcelain gallbladder" (calcification of the gallbladder wall, which is associated with gallbladder carcinoma).

04Management and Treatment

Asymptomatic gallstones do not require treatment. This is one of the most tested concepts. The majority of patients with gallstones (roughly 80%) will never develop symptoms. Prophylactic cholecystectomy is not indicated except in certain high-risk scenarios: a porcelain gallbladder (due to risk of gallbladder carcinoma), very large stones (> 3 cm, which also carry increased cancer risk), and patients with sickle cell disease where differentiating a sickle cell crisis from biliary colic may be difficult in the future.

For symptomatic biliary colic, the definitive treatment is elective laparoscopic cholecystectomy. "Elective" is the key word. Biliary colic is episodic and self-limited, so surgery is scheduled, not performed emergently. During an acute episode, pain is managed with NSAIDs (ketorolac 30 mg IV is commonly cited as first-line) because they reduce gallbladder prostaglandin-mediated contraction. Opioids can be used as second-line but carry a theoretical concern of sphincter of Oddi spasm (though clinically this is debated and should not prevent their use if needed). Dietary modification (low-fat diet) can reduce the frequency of episodes while awaiting surgery, but diet alone is not definitive therapy.

Ursodeoxycholic acid (UDCA) is the only medical dissolution therapy with proven efficacy. It works by reducing cholesterol saturation in bile. It is reserved exclusively for patients who are poor surgical candidates (high anesthetic risk) and who have small (< 1 cm), radiolucent, cholesterol stones in a functioning gallbladder (confirmed by HIDA scan showing cystic duct patency). The dose is 8-10 mg/kg/day divided into two or three doses, taken for 6-12 months. The recurrence rate after successful dissolution is high, approximately 50% within 5 years. UDCA does not work on pigment stones or calcified stones.

If a patient with biliary colic develops persistent pain lasting more than 6 hours, fever, or leukocytosis, the diagnosis has shifted to acute cholecystitis, and management changes to IV antibiotics plus urgent (not elective) cholecystectomy, ideally within 72 hours. Recognizing this transition is a commonly tested decision point.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The single most common trap with cholelithiasis questions is confusing asymptomatic gallstones with symptomatic disease and recommending surgery when observation is the correct answer. If a vignette describes an incidental finding of gallstones on imaging done for another reason, with no history of biliary colic, the answer is reassurance and no intervention. Test-writers love to tempt you with cholecystectomy as an answer choice, banking on the assumption that "stones found = stones removed."

A second high-yield trap is the distinction between biliary colic and acute cholecystitis. Both involve gallstones and RUQ pain. The discriminator is duration and systemic signs: biliary colic resolves within 6 hours, has no fever, no leukocytosis, and a negative Murphy sign. If the vignette describes pain persisting beyond 6 hours with fever or a positive Murphy sign, the diagnosis is cholecystitis, and the management shifts from elective to urgent surgery. Read the timeline and vital signs carefully before choosing your answer.

Another tested concept involves the type of gallstone and its clinical context. When a vignette gives you a young patient with sickle cell disease or hereditary spherocytosis and gallstones, those are black pigment stones from chronic hemolysis. When a vignette describes a patient with biliary infection or parasites, think brown pigment stones. The default in an otherwise healthy patient with typical risk factors is cholesterol stones. The type of stone matters because UDCA only dissolves cholesterol stones.

Finally, remember that plain abdominal X-ray is never the best initial test for gallstones. Even though pigment stones are radiopaque, the majority of gallstones are not. Ultrasound is both the best initial and most accurate test for gallstones within the gallbladder. Do not confuse this with choledocholithiasis (stones in the common bile duct), where ultrasound sensitivity drops and MRCP or endoscopic ultrasound becomes the preferred study. The core competency being tested in cholelithiasis questions is your ability to match the clinical scenario (asymptomatic vs. symptomatic vs. complicated) to the correct management pathway and to avoid overtreating an incidental finding.