Laparoscopic ultrasound (LUS) is a simple and reliable method for evaluating the common bile duct (CBD) during laparoscopic cholecystectomy. It is particularly useful for identifying the location of the CBD and common hepatic duct (CHD) during difficult operative circumstances when the anatomy is obscured. LUS can be performed prior to any potentially hazardous dissection and can easily be repeated as necessary to safely guide dissection. This brief video demonstrates the technique of LUS during routine LC.
A flexible tip probe with a multi-frequency, side viewing, curvilinear transducer is used. Scanning is typically performed at a frequency of 10 MHz. During intraoperative applications, the ability to place the transducer in close contact with the tissue being examined allows use of a higher frequency transducer. Higher frequency ultrasound waves yield better resolution than the lower frequencies that are necessary for adequate depth of penetration during transabdominal imaging.
Fluid is instilled over the hepatoduodenal ligament to improve acoustic coupling. The ultrasound probe, covered by a sterile sheath, is introduced through a 10 mm sub-xiphoid port. The probe is extended to the patients’ right side and then angled to 90 degrees. The bend is maneuvered under the lateral segment of the left liver so that the transducer can be positioned over the hepatoduodenal ligament with light contact.
Scanning is started in a plane transverse to the hepatoduodenal structures. The normal anatomic landmarks are described as depicted in the sonographic image on the video. The junction of the cystic duct with the CBD is identified. The proper hepatic artery (HA) is to the right of the CBD on the screen. The portal vein (PV) is dorsal (“posterior”). The cross sectional image of the PV, HA and CBD together create a “Mickey Mouse” pattern with the cartoon characters’ circular head (PV) below and ears (CBD & HA) on top.
The CBD is traced caudally to the duodenal ampulla which is well seen. This is accomplished by subtle rotation of the operators’ wrist. The internal diameter of the CBD is measured to be 4 mm (normal upper limit 6-7 mm). If present, stones are readily visualized as echogenic structures with posterior acoustic shadowing and sludge as echogenic material without shadowing. The CBD is traced cephalad and the transducer is rotated to yield a longitudinal view of the CBD and PV which appear as parallel tubular structures. In this plane, the right hepatic artery appears as a round structure and is most typically located dorsal to the CHD.
Doppler can demonstrate the characteristic waveforms of the vascular structures, although it is not usually necessary for identification. The PV has a low velocity, continuous forward flow with minor undulations due to cardiac activity. Flow in the inferior vena cava is bi-directional due to the cardiac cycle and respirations. The HA demonstrates features of a low resistance type vessel with a bi-phasic spectral waveform that continues forward during diastole. The CBD has no Doppler signal other than the interference from respiratory excursion. The aorta and right renal artery are also seen at the inferior aspect of the sonographic images.
When the examination has been completed, the flexible probe is straightened and withdrawn under direct vision.
Editor Recruited By: Jeffrey B. Matthews, MD