A number of common laboratory
assays can be used to help narrow the diagnosis in biliary
disease, and exclude other sources of pain in the abdomen.
is a marker of cholestasis. In fact, greater than 90% of
patients with bile stasis will have an elevated alkaline
phosphatase. However, because isozymes of alkaline
phosphatase are found in the liver, bone, placenta, and small
intestine, an elevated alkaline phosphatase, alone, is not
specific for biliary disease.
Bilirubin is the
breakdown product of heme, with the majority coming from
senescent RBC's and (to a lesser extent) from cytochromes and
myoglobin. Unconjugated bilirubin is hydrophobic and
transported in the blood (reversibly) bound to albumen. It
is taken up by liver cells, converted to conjugated bilirubin,
and actively secreted into the biliary canaliculi.
Bilirubin and alkaline phosphatase are used together to evaluate
evidence of common duct obstruction.
Aminotransferases (ALT and AST) are found in the liver,
cardiac, and skeletal muscles. ALT is found predominantly
in the cytosol of hepatocytes, and an elevated ALT is more
likely to suggest liver injury. AST, on the other hand, is
found in both the cytosol and mitochondria, and elevated levels
typically point to hepatocellular injury sustained over a longer
period of time (weeks). The aminotransferases are used to
evaluate the presence of hepatitis and may be elevated in
cholecystitis or with common bile duct obstruction.
commonly ordered on the patient presenting with abdominal pain.
They are used to help exclude pancreatitis as a cause, however,
amylase may also be mildly elevated in cholecystitis.
is typically used to rule out pyelonephritis and renal calculi
as a source of abdominal pain.
Testing should be done on all women of child bearing
Because gallstones are only
radiopaque and seen on plain film x-rays in 10-30% of cases,
ultrasound has become the diagnostic procedure of choice when
evaluating right upper quadrant pain. It is a fast, cheap,
and non-invasive way to look at the biliary system and gain
insightful information when narrowing a diagnosis. It is
particularly good at detecting gallbladder disease and biliary
Ultrasound uses technology similar to sonar. A
two-dimensional image of echoes is created with fluid appearing
black, solid organs appearing hypoechoic, and structures with
high amounts of fat or minimal water appearing hyperechoic.
Gallstones appear as a highly
echogenic focus with acoustic shadows and move to a dependant
portion of the gallbladder. Ultrasound can detect stones
as small as 1-2mm and has a sensitivity on the order of 95% and
a specificity of about 97%.
The presence of a thickened
gallbladder wall, pericholecystic fluid, and a sonographic
Murphy sign (pain elicited when the ultrasound is pressed into
the RUQ on inspiration) supports the diagnosis of cholecystitis.
Because of the interference with
bowel gas, ultrasound has limited capacity in evaluating the
common bile duct, and may miss 25-40% of bile duct stones.
Cholangiography can be used both
intra- and extra-operatively to help visualize the biliary
system. Intra-operative cholangiograms (IOC) are typically
performed during cholecystectomy when there is clinical evidence
that a stone may be present in the common bile duct, however,
some surgeons tend to perform IOC's during any and all
retrograde cholangiopancreatography (ERCP) is an invasive
endoscopic procedure in which radiopaque contrast is injected
into the biliary ductal system under fluoroscopic guidance.
During intra-operative cholangiography, the contrast is
delivered directly into the cystic duct once clamped from the
gallbladder during cholecystectomy. The biliary system (in
both cases) can then be imaged to see if filling defects exist
between the gallbladder and the small bowel (that is, whether
stones are impacted in the common bile duct
(choledocholithiasis) or at the Sphincter of Oddi).
Hepatobiliary scintography (HBS)
uses hepatoiminodiacetic acid (HIDA) or diisopropyl
iminodiacetic acid (DISIDA) in order to study the biliary
system. This test should be ordered when acute
cholecystitis is suspected, as it has been found to be 95%
accurate in diagnosing acute cholecystitis.
Nonvisualization of the gallbladder supports the diagnosis of
acute calculous cholecystitis with a sensitivity and specificity
around 95%. It can also be used to confirm the presence of
a biliary leak. In a typical study, the gallbladder,
common bile duct, and small bladder should fill within 30-45
addition of IV morphine can improve the accuracy of the scan if
the gallbladder is not visualized. Morphine works by
increasing the resistance to flow through the Sphincter of Oddi,
resulting in filling of the gallbladder.