Origin of common duct stones

Primary stones form within the bile duct. They are usually bilirubinate stones of the soft brown type, and they are associated with biliary stasis due to obstruction, infection, and the presence of foreign bodies such as food. In the Orient they are generally caused by infection, sometimes associated with parasites within the biliary tract. However, most common duct stones originate in the gallbladder and migrate through the cystic duct into the common bile duct. These secondary stones consist mostly of cholesterol and often grow in size within the duct.

 

Clinical presentation

Although stones in the bile duct may be silent, the development of symptoms is potentially serious; obstructive jaundice, ascending cholangitis, and acute pancreatitis are all associated with major morbidity and mortality.

 

Less seriously, stones in the ducts may cause bouts of abdominal pain or dyspepsia indistinguishable from symptoms of gallbladder disease or of intermittent biliary colic with transient jaundice. Elderly patients with bile duct stones sometimes present in apparently obscure ways with malaise, confusion, collapse, or septicaemia (Fig. 39) 1262. The cause is often only discovered when routine liver function tests are found to be abnormal. Until recently stones in the bile duct were most commonly discovered at operation. About one in every 10 patients undergoing cholecystectomy was discovered to have stones in the bile duct and required exploration of the duct, although stones were only recovered in perhaps two-thirds of the explorations. Nowadays most bile duct stones are diagnosed by ultrasound and removed endoscopically before cholecystectomy, although surgical exploration of the bile duct is still occasionally necessary.

 

Obstructive jaundice

Occasionally, a small stone passes into the bile duct and impacts at the ampulla, causing pain and jaundice. The severity of the jaundice depends on the duration of the obstruction, but as the stone passes on spontaneously the jaundice resolves. A solitary stone may disappear from the biliary tree in this way, but normally some stones remain in a thick walled gallbladder to support the diagnosis. Such patients need a cholecystectomy, and an operative cholangiogram is essential.

 

More commonly there is a larger stone or stones within a dilated bile duct. Sometimes a large number of stones in the duct leads to a significant impairment of bile flow. At other times a stone moves up and down within the duct and acts as a ball valve, causing pain and jaundice when it impacts but allowing the symptoms to resolve spontaneously when it moves away. The site of impaction is usually immediately above the ampulla, but it may be above a fibrotic narrowing in the bile duct caused by the stones themselves. Complete impaction of a stone causes severe progressive jaundice.

 

Stones in the bile duct usually cause pain. However, it is not easy to distinguish obstructive jaundice due to stones from that due to malignant disease on the basis of pain. Clinical examination normally discloses nothing except a jaundiced patient, and possibly some scratch marks from the intolerable itching. The gallbladder is not palpable since it is thick-walled and fibrotic, and it resists distension, although there is often mild tenderness in the right upper quadrant.

 

Many of these patients are elderly and require prompt endoscopic sphincterotomy and extraction of their stones. Cholecystectomy can be performed later when the jaundice has resolved. In practice only 10 per cent of such patients have continuing symptoms and need surgery. Patients under the age of 50 who are not profoundly jaundiced are best treated by cholecystectomy and exploration of the duct.

 

Ascending cholangitis

Ascending cholangitis is still a fatal disease and it must be treated as a medical emergency. Fortunately it is usually an easy diagnosis to make clinically, as most patients present with the classic symptoms of epigastric pain, rigors, and jaundice (Charcot's triad or Charcot's intermittent biliary fever). Elderly patients sometimes present simply with septicaemia or collapse with little or no jaundice, and rarely the origin of a Gram-negative septicaemia is eventually traced back to the bile duct.

 

Pathology

Cholangitis is always associated with some degree of obstruction within the bile duct: stones in the ducts are the cause in 80 per cent of cases. Many of the patients are elderly. Cholangitis is a rare presentation of malignant biliary obstruction, except in those with carcinoma of the ampulla. Patients with a benign biliary stricture commonly experience recurrent episodes of cholangitis and they always have bacteria in their bile, as do patients with an endoluminal prosthesis in place. Patients with stones nearly always have a positive bile culture, whereas this is only found in 10 per cent of patients with malignant jaundice.

 

Bacteriology

Most of the bacteria cultured from the bile in patients with cholangitis are also found in the bowel. Escherichia coli, Streptococcus faecalis, and Klebsiella species are the most common pathogens, but Staphylococcus, Pseudomonas, and Proteus may occasionally be present. Anaerobic bacteria such as Clostridium perfringens and Bacteroides fragilis, although rarely cultured from gallbladder bile, are an important feature in cholangitis. Bacteria reach the liver in the portal vein and are normally cleared there by the reticuloendothelial system. There is also evidence of cholangiovenous reflux of organisms into the circulation when the systemic symptoms of cholangitis become apparent. More than one organism is present in over half of all patients, and there is some evidence of synergy between the aerobic and anaerobic organisms. Antibiotic treatment, which should always be vigorous, must take account of the polymicrobial nature of most infections.

 

Treatment

The obstructed bile duct must be drained adequately, by the most effective route, and as quickly as possible. However, the patient must first be resuscitated with intravenous fluids and antibiotics. Antibiotic treatment of septicaemia will produce improvement in the patient for a short period, but it will not cure the patient unless the obstruction is relieved. Nowadays this can usually be achieved by an endoscopic sphincterotomy (Fig. 40) 1263, but occasionally conventional surgical drainage is still necessary.

 

Complications

Progression of the septic process within the bile ducts can occur in two separate ways. Sometimes pus develops within the ducts; intrahepatic abscesses may also appear. These abscesses may rupture through the hepatic capsule and give rise to intraperitoneal collections. Purulent cholangitis is often associated with a degree of tension within the biliary system, and there is a gush of purulent bile into the duodenum when the offending stone is released endoscopically.

 

Alternatively the sepsis may become systemic. Progressive renal and cardiac impairment ensues, and patients develop septic shock. Dialysis or haemofiltration may be required. Occasionally, the presenting feature of cholangitis is complete renal failure or cardiovascular collapse; the mortality rate in these patients is very high.

 

Acute pancreatitis

Acute pancreatitis is associated with gallstones (see Section 25.1 170). Impaction of a small stone at the ampulla and occlusion of the pancreatic duct is a cause of pancreatitis in a minority of patients. An early ultrasound examination of the biliary tract is therefore essential in every patient who is admitted with acute pancreatitis, particularly if there is any change in the liver function tests. A few have evidence of stones in the bile duct and an immediate endoscopic sphincterotomy and extraction of the stone is well worthwhile in these patients, as it may abort the episode of pancreatitis immediately. There is no evidence that the pancreatitis is made worse by ERCP, although it is wise to avoid cannulating the pancreatic duct.

 

Mirizzi syndrome

This is an unusual and specific cause of obstruction of the common hepatic duct by a stone impacted in the cystic duct or Hartmann's pouch. The stone may simply press on the bile duct, but more commonly it ulcerates into the duct, creating a cholecysto-choledochal fistula. Patients present with obstructive jaundice, and cholangiography shows narrowing of the bile duct at the porta hepatis, which can have the appearance of a cholangiocarcinoma ( Fig. 41 1264, Fig. 42 1265). The true pathology is eventually identified at surgery, but the operation is often extremely difficult because of severe inflammation and fibrosis. It is best to excise the gallbladder, and it is essential to remove the stone causing the obstruction. If this leaves a large gap in the wall of the bile duct, a biliary enteric bypass is needed. Reconstruction of the bile duct over a t-tube brought out through a separate stab incision is possible for smaller defects.

 

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