Endoscopic retrograde cholangiopancreatography (ERCP) is a standard technique for managing of biliopancreatic diseases [1,2]. Endoscopic retrograde biliary drainage (ERBD) is usually performed under conventional cholangiography (CC) for relief of a biliary obstruction and to ameliorate clinical symptoms. However, CC carries hazards related to radiation exposure and contrast media [3]. CC cannot effectively differentiate small stones or sludge from air bubbles [4]. In addition, CC cannot accurately define the nature of a stricture or the longitudinal spread of cholangiocarcinoma [5].

With the development of optical technology, high resolution intraductal ultrasonography (IDUS) provides more detailed imaged of the biliopancreatic tree and adjacent structures. The flexibility and small diameter of IDUS along with detailed image quality is ideal for evaluating biliopancreatic diseases, such as suspected intraluminal filling defects, indeterminate biliary strictures, and periampullary neoplasms [6]. The sensitivity of IDUS in patients with choledocholithiasis is superior to those of ERCP and abdominal ultrasonography. Cannulation with the IDUS probe into the biliary tree can be performed in most patients without prior endoscopic sphincterotomy (EST). IDUS-directed ERBD can be performed without CC [7,8].

The purpose of this study was to assess the effectiveness and safety of IDUS-directed ERBD (IDUS-ERBD) compared to CC-directed ERBD (CC-ERBD) in patients with an extrahepatic biliary obstruction.

Our results demonstrate the usefulness and safety of the IDUS-ERBD technique for managing a biliary obstruction. The technical success rate of IDUS-ERBD was 100%, which was comparable to that for standard CC-ERBD. In addition, IDUS-ERBD was successfully carried out in all cases without significant complications, such as pancreatitis, cholangitis, or bleeding. The clinical outcomes following ERBD were not different between the two groups. Total procedure time was prolonged slightly using the IDUS-ERBD approach, but the difference was < 4 minutes. Although total procedure time was prolonged mostly by the IDUS procedure, the prolongation of total procedure time in the IDUS-ERBD group may be attributed to the additional concomitant procedures, such as brush cytology or biopsies. Mean radiation exposure time was one-third less in the IDUS-ERBD group than that in the CC-ERBD group.

ERCP with fluoroscopy guidance is a well-established technique for biliary drainage in patients with a bile duct obstruction. The IDUS-ERBD approach has some advantages compared with the CC-directed approach. First, it protects against radiation hazards by minimizing radiation exposure time in patients and the procedure team members, including endoscopists, radiologists, and nursing assistants [10]. Previous reports have demonstrated a linear relationship between radiation dose and fluoroscopy time [11]. ERBD with stent insertion may prolong radiation exposure time to confirm proper placement. Stent insertion is the only independent predictor significantly associated with prolonged fluoroscopy [12]. In the present study, plastic stents were deployed for acute obstructive cholangitis without CC using IDUS guidance in the IDUS-ERBD group. Therefore, the IDUS-ERBD approach significantly decreased radiation exposure time to less than one-third that of the CC-ERBD approach (28.4 seconds vs. 94.2 seconds, p < 0001). Second, the IDUS-ERBD approach can be used as a salvage drainage procedure in patients with severe allergy to iodine because IDUS-ERBD does not use contrast media for ultrasonic cholangiography [13]. The reported incidence of adverse reactions to intravenous iodine-contrast media is 12.6% for mild reactions and 0.22% for severe reactions [14]. It has been demonstrated from experience with iodine contrast used during ERCP that, after this procedure, iodine can be detected in the bloodstream [15]. There have been documented episodes of adverse reactions to iodine-containing contrast media following ERCP [16]. In addition, it may reduce post-ERCP pancreatitis and cholangitis by not using contrast media [17,18]. One of the best ways to decrease the incidence of post-ERCP pancreatitis and cholangitis is to avoid injecting contrast media for cholangiography. However, we did not find differences in the rates of cholangitis, pancreatitis, and hyperamylasemia after the ERBD procedure between the groups. Third, IDUS can provide further information about the biliary tree or ampulla, even for subtle changes, such as small sandlike stones or sludge, small polypoid masses, and details of biliary stricture [6]. Therefore, there was significantly more brush cytology or biopsy in the IDUS-ERBD group compared with CC-ERBD group. Our results show that IDUS provided further diagnoses in eight patients including CBD sludge, extrinsic compression, and malignant stricture in the biliary tree. IDUS can effectively detect small stones < 5 mm compared to those detected by CC. In addition, IDUS can distinguish air bubbles from sludge on ultrasonic cholangiography [4]. IDUS can distinguish a benign from a malignant biliary stricture based on several ultrasonographic criteria, such as disrupted normal bile duct layers, heterogeneous internal echo texture, irregular outer borders, and hypoechoic mass [19-21]. Therefore, IDUS has a potential role for deciding on surgical intervention [22]. Finally, the IDUS-directed technique can be used without fluoroscopic facilities. Therefore, it can be performed at bed side for severely ill patients who cannot move from the intensive care unit [23].

The present study had some limitations. First, the study was a non-randomized retrospective single center study. Second, IDUS-ERBD without CC was performed by a single expert. Third, IDUS-ERBD also has some technical limitations. For example, some patients with tight stricture in the papilla or distal CBD and a large juxtapapillary diverticulum can limit IDUS cannulation [24,25]. An additional EST for inserting the IDUS probe was needed in 25.2% of cases. This result was similar to a previous report that introduced a small-diameter IDUS probe in 75% to 80% of patients without EST [5]. At last, regarding the cost of IDUS-ERBD, the added cost is $208 US dollar compared with that of the CC-ERBD.