The effectiveness of bile cytology during percutaneous transhepatic gallbladder drainage for acute cholecystitis in diagnosing incidental gallbladder cancer

Incidental gallbladder cancers （IGBCs） refer to gallbladder cancers （GCs） that are not preoperatively diagnosed but are diagnosed only after cholecystectomy for benign gallbladder diseases. This exploratory study aimed to investigate the diagnostic performance of bile cytology with percutaneous transhepatic gallbladder drainage （PTGBD） and tumor markers in preoperatively detecting IGBC. Data on consecutive acute cholecystitis cases between January 2018 and March 2020 at the Showa University Hospital in Tokyo, Japan, were retrospectively analyzed. Patient characteristics, bile cytology results, collection date, and blood test results were assessed. Concerning the bile cytology results, classes I–III were categorized as negative, whereas classes IV and V were positive. Bile cytology was performed in 102 patients; of these, 2 cases were diagnosed as GC. The bile cytology results were as follows: class I in 15 cases; class II in 84; class III in 2; class IV in 1; and class V in 0. Therefore, 101 and 1 cases were judged as negative and positive, respectively. Bile cytology had a sensitivity of 50％, specificity of 100％, positive predictive value of 100％, and negative predictive value of 99％. Among 47 patients in whom carcinoembryonic antigen （CEA） and carbohydrate antigen 19-9 （CA19-9） levels were measured, 3 and 12 patients exhibited elevated CEA and CA19-9 levels, respectively. Tumor markers were elevated in IGBC cases; however, several false-positive results were present in cases without GC. Bile cytology from PTGBD may be useful for the preoperative diagnosis of IGBC with acute cholecystitis. Measurement of CEA and CA19-9 levels as tumor markers should be performed with caution, as false-positive results due to inflammation would be included.