Intraductal ultrasound substantiates diagnostics of bile duct strictures of uncertain etiology.

AIM: To report the largest patient cohort study investigating the diagnostic yield of intraductal ultrasound (IDUS) in indeterminate strictures of the common bile duct.
METHODS: A patient cohort with bile duct strictures of unknown etiology was examined by IDUS. Sensitivity, specificity and accuracy rates of IDUS were calculated relating to the definite diagnoses proved by histopathology or long-term follow-up in those patients who did not undergo surgery. Analysis of the endosonographic report allowed drawing conclusions with respect to the T and N staging in 147 patients. IDUS staging was compared to the postoperative histopathological staging data allowing calculation of sensitivity, specificity and accuracy rates for T and N stages. The endoscopic retrograde cholangio-pancreatography and IDUS procedures were performed under fluoroscopic guidance using a side-viewing duodenoscope (Olympus TJF 160, Olympus, Ltd., Tokyo, Japan). All procedures were performed under conscious sedation (propofol combined with pethidine) according to the German guidelines. For IDUS, a 6 F or 8 F ultrasound miniprobe was employed with a radial scanner of 15-20 MHz at the tip of the probe (Aloka Co., Tokyo, Japan).
RESULTS: A total of 397 patients (210 males, 187 females, mean age 61.43 ± 13 years) with indeterminate bile duct strictures were included. Two hundred and sixty-four patients were referred to the department of surgery for operative exploration, thus surgical histopathological correlation was available for those patients. Out of 264 patients, 174 had malignant disease proven by surgery, in 90 patients benign disease was found. In these patients decision for surgical exploration was made due to suspicion for malignant disease in multimodal diagnostics (computed tomography scan, endoscopic ultrasound or magnetic resonance imaging). Twenty benign bile duct strictures were misclassified by IDUS as malignant while 14 patients with malignant strictures were initially misdiagnosed by IDUS as benign resulting in sensitivity, specificity and accuracy rates of 93.2%, 89.5% and 91.4%, respectively. In the subgroup analysis of malignancy prediction, IDUS showed best performance in cholangiocellular carcinoma as underlying disease (sensitivity rate, 97.6%) followed by pancreatic carcinoma (93.8%), gallbladder cancer (88.9%) and ampullary cancer (80.8%). A total of 133 patients were not surgically explored. 32 patients had palliative therapy due to extended tumor disease in IDUS and other imaging modalities. Ninety-five patients had benign diagnosis by IDUS, forceps biopsy and radiographic imaging and were followed by a surveillance protocol with a follow-up of at least 12 mo; the mean follow-up was 39.7 mo. Tumor localization within the common bile duct did not have a significant influence on prediction of malignancy by IDUS. The accuracy rate for discriminating early T stage tumors (T1) was 84% while for T2 and T3 malignancies the accuracy rates were 73% and 71%, respectively. Relating to N0 and N1 staging, IDUS procedure achieved accuracy rates of 69% for N0 and N1, respectively. LIMITATIONS: Pre-test likelihood of 52% may not rule out bias and over-interpretation due to the clinical scenario or other prior performed imaging tests.
CONCLUSION: IDUS shows good results for accurate diagnostics of bile duct strictures of uncertain etiology thus allowing for adequate further clinical management.