This study was approved by the Ethics Committee of our center. From January 2016 to January 2021, 248 patients with BS underwent PTCB combined with biliary drainage in our department. The inclusion criteria for the study were as follows: (1) age range 18–80 years, (2) direct bilirubin (DB) was at least three times higher than the normal value, (3) clinical manifestations were typical for a BS (e.g., jaundice, cholangitis, and fever), (4) Eastern Cooperative Oncology Group (ECOG) score of 0–2, (5) complete clinical data and more than 6 months of follow-up, and (6) platelet count > 50 × 109/L and prothrombin time (PT) ≤ 25 s. The exclusion criteria were as follows: (1) uncontrollable ascites, (2) severe coagulopathy, and (3) severe cardiopulmonary dysfunction. All procedures were performed by the three interventional radiologists at our center who had PTCB experience of 11, 15, and 25 years. The following information was recorded from the patient electronic records: age, sex, operator, PTCB approach (left or right approach), BS site, BS length, imaging findings (eccentricity, rat tail, truncation, and filling defect sign), maximum lesion diameter at the BS area, and final pathological results.

Routine blood testing including liver function, kidney function, electrolytes, coagulation function, and tumor markers as well an electrocardiogram were examined before the procedure. Additionally, both non-contrast and enhanced upper abdomen CT or MR were performed to understand the dilatation of the bile duct, the location of BS, the tumor size, and the planned puncture path.

The patient was laid supine on the DSA (Artis zeego, Siemens, Germany) examination bed, and a mixed solution of dizosin (10 mg) and dexmedetomidine hydrochloride (400 µg) was injected intravenously to obtain a satisfactory analgesic state. After routine disinfection and towel draping at the right costal area, local anesthesia was performed with 2% lidocaine (5 mL) at the skin puncture point, which was determined by preoperative enhanced CT/MR or intraoperative US. A 21-G Chiba needle (Cook, USA) was used to puncture the dilated bile duct, a platinum microwire (0.018 in. × 30 cm) was introduced to the biliary system after cholangiography (320 mg iodine/100 mL, Hengrui, Jiangsu, China, diluted 50% for use), a 6-F dilator was introduced along the micro hydrophilic membrane wire, and another cholangiogram was performed to confirm the BS length and extent. A 0.035-in. wire and 5-F KMP catheter were exchanged with a 6-F dilator, and the BS was opened with the cooperation of the guide wire and catheter until the catheter finally entered the duodenum. Another 0.035-in. strength guide wire (145 cm in length, Radiofocus M, Terumo, Tokyo, Japan) was introduced to establish the skin-bile duct-duodenum approach. Along the guide wire, a 9-F short sheath (23 cm long, cordis, USA) was introduced, whose end was located above the BS segment. After confirmation by angiography, the biopsy forceps (6.0 mm in diameter, Nanjing MicroPort, China) were introduced to the BS through a 9-F sheath, the biopsy forceps were opened and pushed forward for 5–10 mm, and the biopsy forceps were then tightened to clamp the tissue. The biopsy forceps were withdrawn, and the tissue was fixed in a 4% formaldehyde solution. PTCB was repeated three to six times until the sample size met the needs of clinical diagnosis (assessed by a pathologist who had more than 15 years of experience). 8.5-F internal and external drainage tubes (Cook, USA) were introduced after biopsy, and the lateral drainage holes were allowed to cross the BS area. Liver protective and anti-infective drugs were given after the operation for 3–7 days.

Technical success was defined as successfully obtaining enough biliary tissue to complete the pathology examination. The final diagnosis was confirmed by surgery, other histology, or cytology (i.e., percutaneous fine needle aspiration biopsy and bile cytology). If there was no histology or cytology, the patient was followed up for at least 6 months, and the patient was diagnosed as malignant if the size of the lesions was significantly increased and/or metastasis was found by imaging examination. If there was no obvious disease progression in clinical manifestations or imaging findings, it was diagnosed as benign. Diagnostic indicators included sensitivity, specificity, FNV, and false-positive value (FPV). PTCB-related complications were defined according to the International Society of Interventional Radiology (SIR) operating guidelines [14]. In view of multifactorial analysis, malignant tumors are divided into two groups according to their origin: cholangiocarcinoma (malignant tumors originating from the bile duct epithelium) and non-cholangiocarcinoma tumors (malignant tumors other than cholangiocarcinoma, such as pancreatic cancer, gallbladder cancer, hepatocellular carcinoma, duodenal cancer, and hilar metastatic lymph nodes).

Continuous data are expressed as the means ± standard deviation, and a t test was used to compare the indices of alanine aminotransferase, total bilirubin, and direct bilirubin before and 1 week after drainage. Univariate and multivariate logistic regression analyses were used to identify the independent prognostic factors associated with FNV. Statistical analysis was performed using the SPSS software version 21.0 (IBM, Chicago, IL). A p value < 0.05 was considered to indicate a significant difference.