Endoscopic Ultrasonography–Guided Biliary Drainage

Target Identification Under EUS

This relatively simple step should not be overlooked. Before the initial puncture, the endoscopist must carefully explore different access sites within the GI tract so as to choose the optimal approach based on shorter distance to the target, absence of interposed vessels, endoscope stability and least degree of angulation of the echoendoscope, and overall ergonomics. Changes in endoscope position throughout the subsequent steps may compromise procedure success, so time used to assess for the best possible access site is time well spent. As will be discussed below, fluoroscopic landmarks during EUS imaging of the target are also critical for EUS-BD ( Fig. 32.1 ).

Needle Access Into the Target Organ

Standard EUS needles of 19G caliber are most often used, because they reliably allow passage of 0.025-inch and 0.035-inch guidewires. The stiffness of different commercially available 19G needles varies. When the endoscope is in the long position (i.e., within the duodenum), the more flexible 19G needles offer an advantage over stiffer ones. Blunt-tipped 19G needles have also been specifically designed for EUS-BD to prevent wire shearing but have not come into general use. For nondilated targets such as the bile duct or a collapsed small bowel, particularly if there is hard, fibrotic tissue interposed or if the target is very mobile, 22G needles may be used. Some 22G needles allow 0.021-inch guidewires, which is the minimum size required for adequate stiffness to pass accessories. Some 22G needles allow only 0.018-inch guidewires, which are usually too floppy for transmural intervention. For targets requiring 22G needle access, another alternative is the graded injection technique. Two punctures are sequentially made, the initial one with a 22G needle, through which saline and/or contrast is injected to distend the target. Next, the 22G needle is rapidly removed and replaced with a 19G needle, which is then thrust into the distended target. Even when needle access is not a limiting step for EUS-BD, difficulties may be encountered occasionally when trying to puncture ducts across fibrotic tissue. Tenting may occur, with the needle pushing the target away instead of entering it. A quick needle thrust beyond the intended target is often required, and then access is gained by slowly pulling the needle back toward the echoendoscope. Reverse tenting may also occur during needle withdrawal, with the opposite wall of the target catching on the needle. Confirmation of needle access is readily obtained by EUS alone for larger targets. For nondistended small bowel or intrahepatic ducts, aspiration of fluid through the needle and visual confirmation that the aspirated fluid is not blood is useful before proceeding to injection of contrast ( Fig. 32.2 ). If the aspirate is bloody, the needle must be removed into the GI lumen and flushed with saline to prevent clogging. Some authors remove the stylet from the needle before the puncture to allow either priming with contrast or preloading with a guidewire in order to decrease procedure time. However, leaving the stylet in place during puncture may optimize needle performance. Furthermore, a preloaded guidewire prevents fluid aspiration and contrast injection through the needle to confirm entry and fluoroscopic mapping.

Historically, “free-hand” EUS-guided access to the bile duct using needle knives or other cautery-tipped devices was used, but this has been abandoned. More recently, lumen-apposing metal stents (LAMS) with a cautery-enabled delivery system have been successfully used for EUS-guided drainage of pancreatic fluid collections (PFCs; see Chapter 56 ). The free-hand access technique of cautery-tipped LAMS may simplify drainage of PFCs; however, over-the-wire insertion appears to be safer than free-hand insertion of LAMS into the gallbladder or the bile duct. The guidewire protects the contralateral wall from cautery injury during LAMS insertion and helps maintain access in the unlikely (but possible) event of delivery catheter malfunction. These potential difficulties during free-hand access are not an issue when drainage of large, adherent PFC is undertaken but may have serious consequences during biliary or small bowel access. Therefore needles remain the time-honored, standard devices for access under EUS guidance. Low-risk, low-difficulty targets may allow this standard to be changed. But for other types of targets, the challenges for needle access described above may escalate when trying free-hand access with larger-diameter devices, especially when used by less-experienced operators.

Before puncture is attempted, it must be borne in mind that, compared with EUS-guided PFC drainage or cannulation of the papilla during ERCP, the chances for repeat needle access into the bile duct and—to a lesser extent—into the gallbladder are limited. Once an obstructed biliary system is punctured, it rapidly decompresses, making subsequent attempts at puncture more challenging (see Fig. 32.2 ). Contrast and (unintended) air injection further compromise the success of repeated puncture attempts by blurring the ultrasonographic view. Therefore the intended goal is to obtain a successful puncture at the first attempt, both to minimize trauma and the attendant risk of leakage and to maximize the chances of success. This is the reason why the seemingly mundane step number one above is of critical importance.

Contrast Injection and Guidewire Insertion

Contrast delineation under fluoroscopy of the target structure is critical for bile duct drainage and small-bowel anastomosis procedures and very useful but not mandatory for EUS-GBD. Successful cholangiography or enterography eventually serves to confirm access and provide additional guidance throughout the procedure. Even if the gallbladder can be readily imaged and EUS-GBD performed under EUS alone, fluoroscopy is helpful to monitor guidewire looping inside the gallbladder ( Fig. 32.3 ) and to check for contrast leakage, whether iatrogenic from instrumentation or spontaneous from underlying cholecystitis.

Guidewire insertion into the gallbladder or into the GI tract after needle access is straightforward. Standard 0.025-inch or 0.035-inch guidewires are typically used. A more detailed consideration of the type of guidewire is required for EUS-BD, where guidewire manipulation is more demanding (see Fig. 32.1 ). For the gallbladder and the GI tract, guidewire looping is aimed for providing stability throughout the next step of tract dilation, and it is usually easily achieved. Stiff guidewires may push away mobile targets such as the gallbladder or the small bowel. To prevent this, EUS monitoring of the target is maintained during guidewire insertion. The specifics of guidewire insertion and manipulation during EUS-BD will be discussed below.