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is similar to “excavation” of ancient artifacts from soil without causing any damage. Moreover, proficiency
in blood flow control and parenchymal dissection techniques is essential to excavating blood vessels in a dry
operative field during liver parenchymal dissection. In this section, we elaborate on these techniques. These
techniques are essentially the same as open liver surgeries, excluding the external tourniquet system for the
Pringle maneuver and a part of outflow control utilizing several effects of pneumoperitoneum pressure. We
also describe the parenchymal dissection technique utilizing the cavitron ultrasonic surgical aspirator
(CUSA) which is our preference.

BLOOD FLOW CONTROL SKILLS
Blood flow control skills for maintaining a dry operative field during liver parenchymal dissection include
inflow and outflow controls. Generally, the inflow and outflow of blood in the human body can be
controlled because they follow similar paths. However, in the liver, the portions that control inflow and
outflow are distinct; therefore, they must be individually controlled.

Inflow control
Inflow control involves clamping of the hepatoduodenal ligament, thereby occluding the hepatic artery and
portal vein. The Pringle maneuver, which involves the intermittent occlusion of the inflow, has been
extensively adopted as a safe method. Typically, an external tourniquet system comprising a 100 cm-long
polyester tape and a 20 cm-long 22 French-diameter silicone tube is used for this purpose. This tube is
[1]
designed to fit into the hole left by removal of a 5-mm trocar [Figure 1]. Using this external tourniquet
system, initiating and suspending the total inflow occlusion can be performed swiftly, similar to open
hepatectomy.

Outflow control
The blood pressure within the hepatic vein (HV) and inferior vena cava (IVC), known as the central venous
pressure (CVP), is affected by the cardiac pumping motion and positive ventilation pressure and changes
cyclically. During hepatectomy, elevated pressure levels in these vessels can cause the operative field to
[2]
become wet owing to bleeding from small perforations in the HV or IVC . Clamping the root of the HV is
a method to manage the bleeding ; however, encircling the root is not always straightforward or safe for
[3]
[4]
effective clamping. Hence, decreasing the CVP is a widely used alternative approach . One basic means of
[5]
decreasing the CVP is to restrict the venous infusion volume. The reverse Trendelenburg position and
maintaining a low ventilation pressure are also effective approaches. Furthermore, particularly during
[2]
laparoscopic surgery, pneumoperitoneal pressure contributes to a reduction in the extent of bleeding from
the HV.
Bleeding from the HV/IVC is determined by the difference between the blood pressure of the HV/IVC
(venous pressure) and the pneumoperitoneum pressure (abdominal air pressure) . The higher the venous
[2]
pressure relative to the abdominal air pressure, the greater the extent of bleeding, which leads to a wetter
operative field. When the venous pressure equals or falls below the abdominal air pressure, bleeding
diminishes, leading to a drier operative field. However, there is a risk of pulmonary arterial gas embolism
when abdominal air pressure is elevated, although carbon dioxide (CO ) gas can dissolve rapidly in the
2
bloodstream [Table 1].
[2]
PARENCHYMAL DISSECTION TECHNIQUE
Read the grain
Understanding the typical course of blood vessels such as the Glissonean cords and HVs within the liver
parenchyma is valuable when excavating blood vessels that are not visible from the exterior of the liver.