Laboratory Studies
Serum bilirubin levels are elevated in virtually all patients with cholestasis.
Total serum bile salt concentration levels are elevated in virtually all cholestatic diseases.
Qualitative serum and urine bile acids by mass spectroscopy are used to identify genetically determined errors in bile acid synthesis.
The total serum cholesterol level is elevated in virtually all obstructive cholestatic diseases, whereas the high-density lipoprotein (HDL) level is within the reference range or low. Total cholesterol is within the reference range in certain hepatocellular cholestatic diseases, whereas the HDL level is within the reference range or low.
Serum lipoprotein-X levels are elevated in virtually all obstructive cholestatic diseases.
Serum alkaline phosphatase levels, serum 5'-nucleotidase levels, and serum gamma-glutamyl transferase (GGT) levels are elevated in virtually all obstructive cholestatic diseases and most hepatocellular cholestatic diseases.
Imaging Studies
Ultrasonography of liver and bile ducts is used to identify anatomic causes of obstructive cholestasis (eg, choledochal cyst, gallstones).
Abdominal CT scanning is used to identify anatomic causes of obstructive cholestasis (eg, choledochal cyst, gallstones).
Biliary nuclear medicine study (ie, hepatoiminodiacetic acid [HIDA] scanning) is used to identify anatomic causes of obstructive cholestasis (eg, choledochal cyst, gallstones) and to differentiate between obstructive and hepatocellular cholestasis (ie, biliary atresia versus neonatal hepatitis).
Endoscopic retrograde cholangiography is used to identify anatomic causes of obstructive cholestasis (eg, choledochal cyst, gallstones).
Percutaneous transhepatic cholangiography is used to identify anatomic causes of obstructive cholestasis (eg, choledochal cyst, gallstones).
Procedures
Liver biopsy is the single most useful test to determine the cause of cholestasis but requires a high degree of expertise in interpretation.
Exploratory surgery is a very useful tool for diagnosing neonatal cholestasis. Older literature suggested that exploratory surgery placed patients with neonatal hepatitis at risk, but this is not the case with modern anesthesia and surgical techniques. If surgical disease is in question, initiate exploratory surgery to provide a definitive demonstration of bile duct anatomy. In institutions with less experience and expertise, perform exploratory surgery more frequently, rather than less so.
Operative cholangiography is simple, straightforward, time-efficient, and definitive.
Histologic Findings
Many histologic findings are disease specific; therefore, refer to articles about disease states (see Causes). The typical histopathologic features of hepatocellular cholestasis include the presence of bile within hepatocytes and canalicular spaces, in association with generalized cholate injury. Typical of obstructive cholestasis is bile plugging of the interlobular bile ducts, portal expansion, and bile duct proliferation in association with centrilobular cholate injury.
Differentiating between idiopathic neonatal hepatitis and biliary atresia is a diagnostic challenge. With expert evaluation, nothing contributes as much to that differential diagnosis as the findings on percutaneous liver biopsy.
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Eruptive xanthomas. Courtesy of Duke University Medical Center.
