Choledocholithiasis

Background

Symptomatic cholelithiasis is a common medical problem, which makes cholecystectomy one of the most frequently performed surgical procedures in the world. Choledocholithiasis complicates the workup and management of cholelithiasis, necessitates additional diagnostic and therapeutic procedures, and adds to the morbidity and mortality of gallstone disease. Management of choledocholithiasis has been the subject of much debate over the past several years, especially with the advent of new laparoscopic techniques and greater experience with endoscopic procedures.

Pathophysiology

Choledocholithiasis occurs as a result of either the primary formation of stones in the common bile duct (CBD) or the passage of gallstones from the gallbladder through the cystic duct into the CBD. Bile stasis, bactibilia, chemical imbalances, pH imbalances, increased bilirubin excretion, and the formation of sludge are among the principal factors thought to lead to the formation of these stones.

Gallstones are differentiated by their chemical composition. Cholesterol stones are composed mainly of cholesterol, black pigment stones are mainly pigment, and brown pigment stones are made up of a mix of pigment and bile lipids. Obstruction of the CBD by gallstones leads to symptoms and complications that include pain, jaundice, cholangitis, pancreatitis, and sepsis.

Frequency

United States

The incidence rate for gallstones is 10-20%. Approximately 600,000 cholecystectomies are performed in the United States every year, and choledocholithiasis complicates 10-15% of these cases.

International

The international incidence rate is higher, mainly because of the additional problem of primary CBD stones caused by parasitic infestation with Ascaris lumbricoides and Clonorchis sinensis.

Race

Differences in etiology and incidence are observed in persons of different races. In the Asian population, infestation with A lumbricoides and C sinensis is thought to promote bile stasis and, hence, formation of primary CBD stones.

Sex

Cholelithiasis occurs more frequently in females than in males.

Age

In the United States, the incidence rate for gallstones is approximately 40% in individuals older than 60 years. In individuals undergoing cholecystectomy for symptomatic cholelithiasis, 8-15% of patients younger than 60 years have CBD stones, compared to 15-60% of patients older than 60 years.

Clinical

History

Patients with choledocholithiasis may be completely asymptomatic; in approximately 7% of cases, the stones are found incidentally during cholecystectomy. Stones are seen in 1% of autopsies performed on individuals older than 60 years who died of unrelated causes. Approximately 25-50% of asymptomatic CBD stones eventually cause symptoms and require treatment. Symptoms occur when the stones obstruct the CBD. The clinical presentation varies depending on the degree and level of obstruction and on the presence or absence of biliary infection.

• A history of cholelithiasis is not essential for the diagnosis of choledocholithiasis because gallbladder stones can be asymptomatic.
• Pain is the most frequent presenting symptom. The pain is colicky in nature, moderate in severity, and located in the right upper quadrant of the abdomen. The pain is intermittent, transient, and recurrent and may be associated with nausea and vomiting. If the pain is severe, consider a coexisting condition as the primary cause of the pain.
• Jaundice occurs when the CBD becomes obstructed and conjugated bilirubin enters the bloodstream. A history of clay-colored stools and tea-colored urine is obtained from such patients in approximately 50% of cases. The jaundice can be episodic.
• Fever is an indication of cholangitis, and the classic Charcot triad of fever, jaundice, and right upper quadrant pain strongly favors the diagnosis. A recent study on patients with cholangitis showed fever in 92% of patients, jaundice in 65%, pain in 42%, and all 3 in 19%. Cholangitis has a varied presentation, from a mild self-limiting illness to septic shock, observed in 5% of patients.
• Gallstones are responsible for 50% of all cases of pancreatitis. Conversely, 4-8% of patients with gallstones develop pancreatitis. Pancreatitis can be precipitated if CBD obstruction occurs at the level of the ampulla of Vater. Pancreatic pain is different from biliary pain. The pain is located in the epigastric and midabdominal areas and is sharp, severe, continuous, and radiates to the back. Nausea and vomiting are frequently present, and a similar previous episode is reported by approximately 15% patients.
• A history of benign CBD strictures, sclerosing cholangitis, sphincter of Oddi dysfunction, and cystic dilatation of the CBD are important in the diagnosis of secondary biliary stones.
• The presence of parasitic infestation with A lumbricoides or C sinensis may result in the development of primary CBD stones, observed in appropriate populations with the so-called Oriental cholangiohepatitis.

Physical

Specific findings upon physical examination are few and are principally abdominal tenderness and jaundice.

• Tenderness is found in the right upper quadrant of the abdomen. It is moderate in severity, and guarding (voluntary or involuntary) or rebound is absent. Severe tenderness, including the Murphy sign, should suggest the presence of acute cholecystitis, either concomitantly or alone.
• The extent of icterus depends on the severity and duration of CBD obstruction.
• Systemic signs such as fever, hypotension, and flushing may be present and are often indicative of infection, sepsis, or both.

Causes

CBD stones are either primary or secondary. Primary stones arise within the biliary duct system, while secondary stones develop in the gallbladder and migrate to the CBD. In the United States, up to 85% of all CBD stones are secondary in origin.

• Primary CBD stones are caused by conditions leading to bile stasis and chronic bactibilia. Up to 90% of patients with brown pigment CBD stones have bile culture results positive for bacteria. Primary duct stones are usually brown pigment stones. Brown stones differ from black pigment stones by having a higher content of cholesterol. Brown stones are soft and earthy in consistency and take the shape of the duct.
  • In Western populations, biliary stasis is secondary to factors such as sphincter of Oddi dysfunction, benign biliary strictures, sclerosing cholangitis, and cystic dilatation of the bile ducts. Bile stasis promotes growth of bacteria, which produce phospholipase A1, thus releasing fatty acids from biliary phospholipids. The duct epithelium and/or bacteria (eg, Escherichia coli) produce beta-glucuronidase in amounts sufficient to deconjugate bilirubin diglucuronide. The presence of free fatty acids, deconjugated bilirubin, and bile acids leads to the formation of insoluble calcium bilirubinate particles. With the loss of bile acids, cholesterol becomes insoluble, resulting in the formation of biliary sludge. The sludge also contains mucin and bacterial cytoskeletons, which further aid in stone formation.
  • In Asian populations, infestation with A lumbricoides and C sinensis may promote stasis by either blocking the biliary ducts or by damaging the duct walls, resulting in stricture formation. Bactibilia is also common in these instances, probably secondary to episodic portal bacteremia. Some authors have suggested that the stones are formed because of the bactibilia alone and that the parasites' presence is just a coincidence.
• Secondary CBD stones arise from the gallbladder, migrate to the CBD, and have a typical spectrum of cholesterol stones and black pigment stones. Bacteria can be cultured from the surface of cholesterol and pigment stones but not from the core, suggesting that bacteria do not play a role in their formation.
  • The prerequisites for the formation of cholesterol stones are cholesterol supersaturation, stasis, and accelerated nucleation. The sex of the patient, parity, obesity, weight loss, and genetics are risk factors for the development of cholesterol stones.
  • Black pigment stones typically occur in conditions in which bilirubin excretion is increased, as in hemolytic disorders and in situations associated with profound gallbladder stasis such as prolonged fasting and long-term parenteral nutrition. Pigment stones are more common in patients with cirrhosis and ileal disease, although the exact mechanism of stone formation under these conditions is not understood.