The use of intraductal ultrasound at endoscopic retrograde cholangiopancreatography
(ERCP) enables the identification of more than 95 % of common bile duct stones, regardless
of their size or composition, or the diameter of the duct [1]. However, false-positive studies have been reported to occur because of the inherent
difficulty of differentiating common bile duct stones from air bubbles using intraductal
ultrasound [1]. To overcome this limitation and achieve optimal imaging, we propose a new technique
that can be adopted when intraductal ultrasound is performed at ERCP.
We prospectively evaluated ten patients who underwent intraductal ultrasound during
ERCP for evaluation of “indeterminate” common bile duct filling defects. All the patients
had undergone prior biliary sphincterotomy. These “indeterminate” common bile duct
filling defects were defined as those defects identified in patients in whom an occlusion
cholangiogram using a stone retrieval balloon had not been able to differentiate common
bile duct stones from air bubbles. Intraductal ultrasound was performed using a 20-MHz
ultrasound catheter probe (UM G20 – 29R; Olympus, Melville, New York, USA) connected
to a standard endoscopic ultrasound processor (Olympus EU-M30). A 0.035-inch guide
wire was first placed in the intrahepatic bile duct and the intraductal ultrasound
catheter probe was advanced over the guide wire and slowly withdrawn in a stepwise
fashion.
Intraductal ultrasound definitions were: an echo-rich focus in the bile duct, with
or without acoustic shadowing, for common bile duct stones; comet-shaped echoes with
acoustic shadowing or fan-shaped echo-rich signals for air bubbles; and variably shaped
echoes and easily distorted echo-rich structures without acoustic shadowing for sludge
[1]. As the intraductal ultrasound image quality in our patients was poor because of
inadequate acoustic coupling due to pneumobilia, an ERCP catheter was introduced into
the common bile duct, alongside the intraductal ultrasound probe, and 25 ml of normal
saline was flushed into the common bile duct (Figure [1]). The intraductal ultrasound probe was then gradually withdrawn. Better acoustic
coupling enabled visualization of residual sludge/stones in seven of the ten patients,
which were extracted using a stone retrieval balloon/basket (Figure [2]). In the three other patients the common bile duct appeared normal.
Figure 1 An endoscopic retrograde cholangiopancreatography catheter was introduced into the
common bile duct, alongside the intraductal ultrasound probe, to flush normal saline
into the common bile duct.
Figure 2 Better acoustic coupling after irrigation of normal saline into the common bile duct
enabled visualization of biliary sludge that had not been seen previously.
Flushing normal saline into the common bile duct during intraductal ultrasound examination
improves acoustic coupling and enables reliable differentiation of common bile duct
stones from air bubbles.
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