The major subdivisions of the biliary tract are the intrahepatic bile ducts, the common bile duct, and the gallbladder. The major diseases of the extrahepatic biliary system are gallbladder inflammation (cholecystitis, acute or chronic), gallbladder stones, and obstruction to the common bile duct by stones or tumor. Obstruction to intrahepatic bile channels can occur as a result of acute hepatocellular damage, but this aspect was noted in the discussion of liver function tests and will not be repeated here.

Acute cholecystitis usually presents with upper abdominal pain, most often accompanied by fever and a leukocytosis. Occasionally, difficulty in diagnosis may be produced by a right lower lobe pneumonia or peptic ulcer, and cholecystitis occasionally results in ST and T wave electrocardiographic changes that might point toward myocardial disease. Acute cholecystitis is very frequently associated with gallbladder calculi, and 90%-95% have a stone in the cystic duct. Some degree of increased bilirubin level is found in 25%-30% of patients, with a range in the literature of 6%-50%. Bilirubinemia may occur even in patients without stones. Acute cholecystitis without stones is said to be most common in elderly persons and in patients who are postoperative. AST may be elevated in nearly 75% of acute cholecystitis patients; this is more likely if jaundice is present. In one study, about 20% of patients had AST levels more than 6 times normal, and 5% had levels more than 10 times normal. Of these, some had jaundice and some did not. Alkaline phosphatase levels are elevated in about 30% of patients with acute cholecystitis. Cholecystitis patients sometimes have an elevated serum amylase level, usually less than 2 times normal limits. About 15% of patients are said to have some degree of concurrent acute pancreatitis.

In our own hospital, of 25 consecutive surgical patients with microscopically proven acute cholecystitis, admission levels of total bilirubin, AST (SGOT), and ALP were all normal in 56% of the patients. Interestingly, all three tests were normal in some patients who had severe tissue abnormality. Total bilirubin, AST, and ALP were all elevated in 12% of the 25 patients. AST was elevated in 36% of the 25 patients, with about half the values less than twice the upper reference range limit and the highest value 7.5 times the upper limit. AST was the only value elevated in 16% of the 25 patients. ALP was elevated in 28% of the 25 patients; the highest value was three times the upper reference limit. The ALP was the only value elevated in 8% of the 25 patients. AST and ALP were elevated with normal total bilirubin in 8% of the 25 patients.

About 20% of patients with acute cholecystitis are reported to have common duct stones. In one series, about 40% of patients with common duct stones did not become jaundiced, and about 20% had an elevated bilirubin level less than 3 mg/100 ml. Common duct stones usually occur in association with gallbladder calculi but occasionally are present alone. In one study, 17% of patients with common duct stones had a normal ALP level; in 29%, the ALP level was elevated to less than twice normal; 11% had values between two and three times normal; and 42% were more than three times normal.

In uncomplicated obstructive jaundice due to common duct stones or tumor, AST and LDH values are usually normal. Nevertheless, when acute obstruction occurs, in some instances AST levels may become temporarily elevated very early after the onset of obstruction (sometimes with AST levels more than 10 times normal) in the absence of demonstrable hepatocellular damage. The striking AST elevation may lead to a misdiagnosis of hepatitis. Several reports indicate that LDH levels are also considerably elevated in these patients, usually 5 times the upper limits of normal. Since LDH levels are usually less than twice normal in hepatitis virus hepatitis (although occasional exceptions occur), higher LDH values point toward the “atypical obstruction” enzyme pattern. Both AST and LDH values usually fall steadily after 2-3 days.

Radiologic procedures

Diagnosis of stones in the gallbladder or common bile duct rests mainly with the radiologist. On plain films of the abdomen, 20%-25% of gallbladder stones are said to be visible. Oral cholecystography consists of oral administration of a radiopaque contrast medium that is absorbed by intestinal mucosa and secreted by liver cells into the bile. When bile enters the common duct, it takes a certain amount of pressure to force open the ampulla of Vater. During the time this pressure is building up, bile enters the cystic duct into the gallbladder where water is reabsorbed, concentrating the bile. This process allows concentration of the contrast medium as well as the bile and, therefore, outlines the interior of the gallbladder and delineates any stones of sufficient size. An average of 70% of patients with gallbladder calculi may be identified by oral cholecystography. Repeated examination (using a double dose of contrast medium or alternative techniques) is necessary if the original study does not show any gallbladder function. In most of the remaining patients with gallbladder calculi, oral cholecystography reveals a poorly functioning or a nonfunctioning gallbladder. Less than 5% of patients with gallbladder stones are said to have a completely normal oral cholecystogram. (More than 50% of patients with cholecystitis and gallbladder tumor have abnormal oral cholecystograms.)

There are certain limitations to the oral method. Although false negative examination results (gallbladder calculi and a normal test result) are relatively few, false positive results (nonfunctioning gallbladder but no gallbladder disease) have been reported in some studies in more than 10% of cases. In addition, neither oral cholecystography nor plain films of the abdomen are very useful in detecting stones in the common bile duct. Visualization of the common bile duct by the oral method is frequently poor, whether stones are present or not.

IV cholecystography supplements the oral procedure in some respects. Nearly 50% of common duct stones may be identified. Intravenous injection of the contrast medium is frequently able to outline the common duct and major intrahepatic bile ducts. However, IV cholecystography is being replaced by other techniques such as ultrasound, because limitations of the IV technique include poor reliability in demonstrating gallbladder calculi (since there are an appreciable number of both false positive and false negative results) and a considerable incidence of patient reaction to the contrast medium (although newer techniques, such as drip infusion, have markedly reduced the danger of reaction).

A limitation to both the oral and the IV procedure is that both depend on a patent intrahepatic and extrahepatic biliary system. If the serum bilirubin level is more than 2 mg/100 ml (34 µmol/L) (and the increase is not due to hemolytic anemia), neither oral nor IV cholangiography is usually satisfactory.

Ultrasound is another very useful modality in the diagnosis of cholecystitis. Sensitivity is about the same as that of oral cholecystography (94%-95%; literature range, 89%-96%). However, ultrasound gives fewer false positive results < 5%). Ultrasound visualizes more stones than oral cholecystography, which is an advantage in deciding whether or not to perform surgery. For example, one study showed that ultrasound detected twice as many calculus-containing gallbladders in patients with nonfunctioning gallbladders than oral cholecystography. In addition, ultrasound can be performed the same day that the diagnosis is first suspected and is not affected by some factors that make oral cholecystography difficult or impossible (e.g., a severely ill patient, severe diarrhea or vomiting, jaundice, pregnancy, and sensitivity to x-ray contrast media). Therefore, some physicians use ultrasound as the first or primary procedure in possible cholecystitis. Others perform single-dose oral cholecystography first, and if the gallbladder does not visualize but no stones are found on first examination, ultrasound is performed.

CT was discussed earlier. It is generally not ordered in acute cholecystitis unless there is suspicion of additional problems in the gallbladder area or in the abdomen.

Biliary tract radionuclide scanning is becoming available in larger centers using technetium-labeled iminodiacetic acid (IDA) complexes such as diisopropyl-IDA (DISIDA), which are extracted by the liver and excreted in bile. Normally the gallbladder, common bile duct, and isotope within the duodenum can be visualized. In acute cholecystitis there is cystic duct obstruction, and the gallbladder does not visualize on scan. This technique is said to have a sensitivity of 95%-98% with less than 5% false positive results. Many consider it the current procedure of choice in acute cholecystitis. Standard gray-scale ultrasound is not quite as good in detecting acute cholecystitis as it is in detecting chronic cholecystitis, although real-time ultrasound sensitivity is said to be 95% accurate or better. The ability of ultrasound to visualize stones is an advantage, but radionuclide scanning has an advantage in patients with acute acalculous cholecystitis. Radionuclide scan diagnosis of chronic cholecystitis is not nearly as accurate as detection of acute cholecystitis, and the technique usually does not visualize stones. Because the common duct can be visualized even when the serum bilirubin level is elevated, DISIDA scanning can also be useful in early or acute extrahepatic obstruction. In early or acute common duct obstruction the common duct may not yet be sufficiently dilated to produce abnormal ultrasound sonograms or abnormal CT scans. However, in long-standing obstruction, hepatic parenchymal cells are injured and cannot extract the IDA compounds from the blood sufficiently well to consistently fill the common duct. If symptoms persist or if there is a suggestion of complications, DISIDA scanning is useful after biliary tract operations.

One report indicates a significant number of false positive results (gallbladder nonvisualization) in patients who have alcoholic liver disease and in patients on total parenteral nutrition therapy.