Chapter 32 Cholelithiasis and cholecystitis
1 The two main types of gallstones are cholesterol and pigment. The pathogenesis of cholesterol and pigment stones is different, but the clinical syndromes they cause are similar.
2 Most gallbladder stones are asymptomatic. When they become symptomatic, biliary pain is the most common manifestation. Hallmarks of biliary pain are its episodic nature and location in the upper abdomen, usually in the right upper quadrant. Other conditions may coexist with gallstones and account for symptoms attributed initially to the stones.
3 The treatment of choice for symptomatic gallbladder stones is laparoscopic cholecystectomy; when this approach is not feasible, open cholecystectomy is the alternative. Magnetic resonance cholangiopancreatography (MRCP) or endoscopic retrograde cholangiopancreatography (ERCP) may be used to investigate for bile duct stones preoperatively.
4 Acute cholecystitis is the most common complication of gallstones. Cholecystectomy is the treatment of choice. Consultation with the internist, gastroenterologist, and surgeon is warranted to arrive at the most efficient plan for care.
Classification of Gallstones
1. Gallstones are common worldwide and, although mostly asymptomatic, can result in a wide spectrum of symptoms and presentations.
3. Cholesterol and pigment stones have distinctly different compositions, pathogeneses, and clinical associations.
4. In the United States and other Western countries, most (generally 80% to 90%) stones in the gallbladder are cholesterol stones. Pigment stones comprise the remainder. In some South American countries, pigment stones are rare. In some East Asian countries, the proportion of pigment stones is significantly higher than that in Western countries.
5. The clinical syndromes caused by gallstones in the gallbladder are similar regardless of the type of stone involved.
Cholesterol stones
1. These stones are composed primarily of cholesterol (proportion varies, generally greater than 60%) and mucin, calcium salts of bilirubin, phosphate, carbonate, and palmitate, and small amounts of various other substances. “Pure” (100%) cholesterol stones account for approximately 10% to 15% of all cholesterol stones.
2. Some stones contain less than 60% cholesterol but have the morphologic and microstructural features of typical cholesterol stones; these are termed mixed stones.
Pigment stones
2. The two types of pigment stones are black and brown.
a. Black pigment stones: black and composed primarily of calcium bilirubinate and other pigment, mucin, calcium salts of phosphate and carbonate, and small amounts of various other substances. These stones are found almost exclusively in the gallbladder and only rarely in the bile ducts (BDs). Most patients have no identifiable predisposing condition. The major known associated conditions are as follows:
b. Brown pigment stones: typically brown and composed primarily of calcium bilirubinate, cholesterol, calcium palmitate, and small amounts of various other substances These stones are found mostly in the BDs and, in East Asia, frequently in the gallbladder as well; in Western countries, brown stones in the gallbladder are unusual.
Pathogenesis
Cholesterol stones
1. Supersaturation of bile with cholesterol (cholesterol saturation index [CSI] greater than 1.00) is a necessary but not sufficient condition. Also thought to be important are an absolute or relative increase in gallbladder mucin, other nucleating factors, and calcium ions and possibly a decrease in antinucleating factors. Gallbladder stasis plays a role in some cases.
2. Initial events in cholesterol stone formation involve the nucleation of cholesterol monohydrate crystals from biliary cholesterol-phospholipid vesicles and formation of a stone nidus by an aggregation of calcium salts, pigment, and/or mucin. The nucleation time of gallbladder bile (time to formation of cholesterol crystals) in patients with cholesterol stones is significantly shorter than that in normal controls.
Pigment stones
1. Black pigment: Precipitation of calcium salts and pigment is the major pathophysiologic event. Failure to maintain calcium ions in solution is considered important, resulting in the precipitation of calcium bilirubinate, phosphate, and carbonate. Gallbladder mucin is thought to act as a nucleating factor, and other nucleating factors are postulated to be involved.
2. Brown pigment: Precipitation of calcium bilirubinate and calcium salts of fatty acids is the major pathophysiologic event. Beta glucuronidase from bacterial or tissue sources is important in deconjugating bilirubin and in causing its precipitation with calcium; an analogous process is thought to result in fatty acid precipitation. Biliary stasis and bacteria in bile are believed to be important for stone formation.
Diagnosis
2. Computed tomography (CT)
Not as sensitive as ultrasonography because some stones do not contain enough calcium to be detected
Not as sensitive as ultrasonography because some stones do not contain enough calcium to be detected
Natural History
Asymptomatic gallstones
Increased use of ultrasonography in the evaluation of abdominal pain has led to the identification of incidental gallstones. Most patients with gallstones are asymptomatic and remain asymptomatic after decades of follow-up. The rate at which asymptomatic patients develop biliary pain is approximately 1% to 2% annually. The risk of presenting initially with a complication rather than with biliary pain alone is low. Because the rate of developing symptoms is low, the consensus is that asymptomatic patients with gallstones should not undergo prophylactic cholecystectomy.
