Diagnosis of bile duct cancer by bile cytology: usefulness of post-brushing biliary lavage fluid

BACKGROUND Pathologic evidence of biliary diseases can be obtained from cytology in addition to endoscopic retrograde cholangiopancreatography (ERCP); however, the diagnostic effectiveness is not satisfactory. STUDY AIM This retrospective, single-center study evaluated the efficacy of various sampling methods for the cytologic diagnosis of bile duct cancer. PATIENTS AND METHODS Biliary samples included bile that was simply aspirated, brush smear, brush-rinsed saline, and post-brushing biliary lavage fluid. A set of samples was compared for cytologic efficacy in 76 patients with surgically proven bile duct cancer and in 50 patients with benign biliary stricture. RESULTS The cytologic sensitivity for diagnosing biliary cancer was 34 % with aspirated bile, 32 % with brush smear, 43 % with brush-rinsed saline, and 70 % with post-brushing biliary lavage fluid, in contrast to the null false-positive result in the benign cases. The sensitivity of cytology was significantly higher with post-brushing lavage fluid than with the other three sampling methods (P < 0.0001), and post-brushing lavage fluid improved the cumulative sensitivity by 24 % (P = 0.002). The sensitivity of biliary cytology was also associated with the amount of aspirated bile (P = 0.01) and with the aspiration site (P = 0.03). The rate of cancer positivity in a cytology set differed according to the tumor macroscopic type (85 % in the protruding type vs. 40 % in the flat type; P = 0.003), and according to the size of the cancer (87 % for tumors ≥ 50 mm vs. 66 % for tumors < 50 mm; P = 0.02). CONCLUSIONS Post-brushing biliary lavage fluid cytology provides superior diagnostic efficacy, and its addition to ERCP procedures is recommended for obtaining cytologic evidence of bile duct cancer.