In the evaluation of suspected biliary tract disease the complete blood count with differential (CBC with diff.) is most frequently utilized to assess the possibility of bacterial infection. Acute bacterial infection typically results in neutrophilic leukocytosis i.e. an increased number of white blood cells (WBC count >10,500) with an elevated percentage of neutrophils (>70%). Besides an increase in total neutrophil count, immature neutrophils, also known as bands, are often present. This is known as a "left shift" with greater than 5% bands considered abnormal.
Cholelithiasis and choledocholithiasis do not cause leukocytosis, neutrophilia, or a left shift, as there is no infection or significant inflammation present.
Acute cholecystitis is classically associated with leukocytosis, elevated neutrophil count, and a left shift. Although many texts describe leukocytosis as a requisite diagnostic finding in patients with acute cholecystitis, this is not the case. While an elevated WBC count is typical, up to 32% of patients presenting with acute cholecystitis have a normal WBC count.(1)
Patients with cholangitis nearly always exhibit leukocytosis, neutrophila, and a left shift, as this is often a suppurative and rapidly progressive infection. The WBC count often exceeds 20,000.
In gallstone pancreatitis, WBC count may or may not be elevated and is thus not diagnostically specific, but a WBC count greater than 16,000 at presentation is one of Ranson's criteria and is established as a poor prognostic sign.
When utilizing WBC count to evaluate any patient, it is important to bear in mind that many of the most vulnerable patients including the elderly, immunocompromised, and those with overwhelming infection may be those least capable of mounting a WBC response. Thus, laboratory studies, especially WBC count and differential, are useful adjuncts in the diagnosis of biliary tract disease but must be considered in the context of information gained from the history, physical exam, and other laboratory and imaging studies.
2. Ravel, R. Ravel: Clinical Laboratory Medicine, 6th ed. Mosby Year Book Inc. 1995.