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Chapter 12 / Intraoperative Ultrasound of the Liver, Bile Ducts, andPancreas 151
INTRAOPERATIVE ULTRASOUND OF THE PANCREAS
Ultrasound is a remarkably useful but generally underused modality with
which to evaluate pancreatic pathology. Similar to most tools, the more one
uses ultrasound for pancreatic evaluation, the more comfortable the opera-
tor becomes with the approach and the more they appreciate the broad
variety of applications of this modality.
Systematic Approach
Ultrasound of the pancreas should be performed both using an acoustic
window such as the stomach or duodenum as well as by placing the probe
directly on the pancreatic parenchyma to appreciate improved resolution.
Systematic approach to the pancreatic ultrasound involves evaluation of the
parenchyma, pancreatic duct, vascular relationships, and the target lesion
(i.e., tumor, stone, dominant stricture). e pancreas relationship to adjacent
vascular structures such as the splenic vein/superior mesenteric vein conu-
ence (Fig. 12.10) provides useful points of reference (i.e., pattern recognition).
Pancreatic Parenchyma
Normal pancreatic parenchyma is usually homogeneous, with a small,
anechoic or hypoechoic duct visible. e typical “salt and pepper” speckled
features of the pancreatic parenchyma is due to the hyperechogenic intra-
parenchymal fat. Pancreas echogenicity is usually similar to or greater than
that of the liver.
Features of chronic pancreatitis have been dened to include parenchy-
mal (hyperechoic foci, hyperechoic strands, hypoechoic lobules, and cysts)
and ductal (dilation, dilated side branches, main duct irregularity, hyperechoic
duct margins, and stones) criteria (Fig. 12.11). Table 12.2 outlines the se criteria.
FIGURE 12.10 Transverse orientation at the pancreatic head. Superior mesenteric vein
(SMV) (in A) and SMV/splenic vein conuence (in B) are shown with long arrow
; pancreatic
duct at the genu (A) and body (B) is shown with short arrows.
Section II / Liver152
Pancreatic Duct
e pancreatic duct should be evaluated for size, tortuosity, known (or
unappreciated), strictures, the presence of pancreatic divisum, and/or size
of accessory pancreatic duct, which has implications when planning trans-
duodenal sphincteroplasty. A minimally dilated or tortuous pancreatic
duct may be very challenging to open longitudinally if one is considering
a lateral pancreaticojejunostomy; direct IOUS guidance is quite help-
ful in this circumstance. Perhaps, the most important relationship of the
pancreatic duct is that of the main pancreatic duct to a cyst or neuroen-
docrine neoplasm if the operator is considering enucleation. Injury to the
main pancreatic duct results in a high-volume, morbid pancreatic stula.
FIGURE 12.11 Chronic pancreatitis showing main
pancreatic duct stricture (short arrow) with dilation of
MPD upstream to the tail (long arrow).
Parenchymal
Hyperechoic foci
Hyperechoic strands
Hypoechoic lobules
Cyst
Ductal
Irregular duct contour
Visible side branches
Hyperechoic duct margin
Dilated main duct
Stones
Ultrasound Characteristics of Chronic Pancreatitis
TABLE
12.2
Chapter 12 / Intraoperative Ultrasound of the Liver, Bile Ducts, andPancreas 153
e intrapancreatic portion of the common bile duct should be evaluated
routinely for size, intraluminal lesion, and relationship to pancreatic ducts.
Vascular Relationships
Vascular relationships include relation of the pancreas and target lesion to
the surrounding arterial and venous structures: portal, splenic, and superior
mesenteric veins, and celiac, hepatic, gastroduodenal, and superior mesen-
teric arteries. is relationship is unique to individual lesion/tumor posi-
tion. Often the splenic artery is intraparenchymal in the body and the tail of
the pancreas. erefore, understanding splenic arter y anatomy is important
when the operator is considering spleen preserving distal pancreatectomy
or lateral pancreaticojejunostomy (which should be extended to the tail).
Unusual anatomy such as a replaced right or left hepatic artery is important
and may be recognized with the IOUS. e presence and/or extent of portal
vein/superior mesenteric vein or splenic vein thrombosis can be identied
and again may have direct implications on operative planning.
Target
Finally, in the systematic approach to pancreas IOUS is evaluation of the
target lesion. Tumors should be evaluated for their relationship to adjacent
vasculature (i.e., superior mesenteric/portal veins, superior mesenteric
artery,) as well as to adjacent organ structures such as the stomach, adre-
nal, and colon in the case of pancreas tail tumors. Deliberate characteriza-
tion of tumor echogenic features will inform the operator’s future practice.
For example, pancreatic adenocarcinoma is typically hypoechoic; distal
cholangiocarcinoma may not obstruct the pancreatic duct (Fig. 12.12);
FIGURE 12.12 Longitudinal view of a metal biliary
stent passing through well-circumscribed, hypoechoic
distal cholangiocarcinoma (arrows). The pancreatic duct
in this patient was not dilated.
Section II / Liver154
and neuroendocrine neoplasms are typically hyperechoic and well-circum-
scribed relative to surrounding parenchyma (Fig. 12.13).
Dominant strictures in the pancreatic duct should be identied; in
addition, ultrasound provides a sensitive method to interrogate the entire
ductal system for other unexpected strictures, which may inuence the
choice of operation, particularly in chronic pancreatitis patients.
Pancreatic cysts are easily identied and characterized by IOUS
(Fig. 12.14). Attention should be directed toward communication with the
main pancreatic duct, wall irregularity, or mural nodularity. In addition, the
relationship of the cyst to surrounding structures including the main pan-
creatic duct is important, especially if considering enucleation.
IOUS is the most accurate method with which to characterize peri-
pancreatic inammatory collections in the setting of necrotizing pancre-
atitis (Fig. 12.15). e volume of solid necrosis has major implication in
treatment planning.
Pearls
■ Fine tuning TGC is particularly useful when evaluating the vascular/
tumor interface.
■ Knowledge of the relationship between cysts or islet cell tumors and the
■ In laparoscopic IOUS evaluation of the pancreas, port placement is impor-
tant. e pancreas should be scanned from at least two separate ports.
e operator should also be aware that probe orientation and the result-
ing image will change signicantly with dierent fulcrum of laparoscopy.
FIGURE 12.13 Transverse view of a pancreas neuroendocrine
tumor is hyperechoic and well circumscribed, with hypoechoic
edges and faint posterior shadowing. Superior mesenteric vein
is shown with arrow.
Chapter 12 / Intraoperative Ultrasound of the Liver, Bile Ducts, andPancreas 155
■ Evaluation of the pancreatic duct is important when considering open-
ing a small pancreatic duct for lateral pancreaticojejunostomy.
■ It bears repeating that ultrasound is the most accurate way to iden-
tify solid versus uid peripancreatic necrotic debris in the setting of
necrotizing pancreatitis.
FIGURE 12.14 Transverse orientation, laparoscopic IOUS of
pancreatic tail mucinous cystic neoplasm (MCN; arrow). Note
thick walls and internal septae. Note also relationship to the
left kidney (star).
FIGURE 12.15 Transgastric view (transverse orientation) of peripancreatic
collection in necrotizing pancreatitis patient. This collection has uid (stars)
and solid (arrows) components.
Section II / Liver156
INTRAOPERATIVE LAPAROSCOPIC ULTRASOUND
Laparoscopic ultrasound follows the same principles as other IOUS tech-
niques. e major dierence is limited probe motion based on probe rigid-
ity and the fulcrum of the probe interface through the abdominal wall
(Fig. 12.16). Laparoscopic probes that articulate in one and two directions
provide better tissue coverage than rigid probes (Fig. 12.3). Laparoscopic
ultrasound is technically and intellectually more demanding than open
IOUS, with an attendant longer learning curve. Laparoscopic IOUS should
be performed through multiple ports (i.e., umbilical, subxiphoid, lateral).
e operator should concentrate on understanding image patterns that
may be markedly dierent from traditional (open) IOUS patterns.
CONCLUSION
In summary, intraoperative ultrasonography is an extremely valuable addi-
tion to the HPB surgeon’s armamentarium. Performing ultrasound on every
case is helpful to understand both normal parenchymal and anatomic
relationships as well as becoming familiar with pathology and unusual
relationships.
Suggested Readings
Choti MA, Kaloma F, de Oliveira ML, et al. Patient variability in intraoperative
ultrasonographic characteristics of colorectal liver metastases. Arch Surg
2008;143(1):29–34.
Connor S, Barron E, Wigmore SJ, et al. e utility of laparoscopic assessment in the
preoperative staging of suspected hilar cholangiocarcinoma. J Gastrointest Surg
2005;9(4):476–480.
Hagopian EJ, Manchi J, eds. Abdominal ultrasound for surgeons. New York, NY:
Springer, 2014.
FIGURE 12.16 Laparoscopic ultrasound scanning from several different ports.
(From Machi J, Staren E, eds. Ultrasound for surgeons, 2nd ed. Philadelphia,
PA: Lippincott Williams & Wilkins, 2005.)
157
BACKGROUND
e rst well-documented reports of deliberate resection of liver tumors
come from A. Luis in 1886 and Carl von Langenbuch in 1887, both of
which were marred by postoperative bleeding. Control of the hepatic
bleeding was accomplished with “well-placed sutures and well-timed
prayers.” William Williams Keen was credited with rst liver resection
in America and also described the “nger fracture” technique and indi-
vidual cauterization. In1888, Hugo Rex and, in 1897, James Cantlie from
Liverpool rediscovered the work of Glisson from 1654 and described the
avascular plane through the gallbladder bed toward the vena cava, now
known as the Rex-Cantlie line. is was followed by description of the
Pringle maneuver, and nally the seminal work of Claude Couinaud, in
1954, on the segmental architecture of the liver, led to the blossoming of
modern-day hepatic surgery. e nger fracture technique was initially
described and was followed later by the clamp–crushing technique or
Kelly-clysis, which has since become the reference parenchymal transec-
tion method. Following these anatomical principles and improvement in
anesthesia, surgeons could attain anatomical resection with less blood
loss, but the problem of bleeding parenchyma, erratic vasculature, high
mortality, and morbidity persisted. At the same time, it has been shown
clearly that the use of blood transfusions in liver surgery is associated with
worse outcomes. In an attempt to decrease blood loss and improve tran-
section speed and quality, various hemostatic assist energy devices have
been designed.
Although great advances have been made in technology, the ideal
hemostatic energy device and mechanism is a topic of much debate. e
ideal coagulation mechanism would include ease of use, minimal lateral
energy damage, the ability to cut as well as coagulate, control of tissue
temperature (so that charring is avoided), reliability, noninterference with
medical devices, and the versatility to work on a variety of tissues. We will
individually examine the commonly used energy sources, review current
literature, and compare their strengths, weaknesses, and uses.
ELECTROSURGERY
ermal and chemical cauteries were the rst tools for hemostasis. is
technique evolved over time to the use of electrocautery or more accurately
electrosurgery, since it involves the use of an alternating current in which
the patient is part of the circuit. e principle is generation of electricity
from the Electro-generator unit, delivered to a handheld device, which
then uses tissue impedance to produce heat. e complementary part of
the circuit, return electrode, or grounding pad takes the electrons back to
complete circuit.
Energy Devices for
Parenchymal Transection in
Liver Surgery
Prejesh Philips and Robert C.G. Martin II
13
Section II / Liver158
Monopolar high-frequency electrical energy is the oldest method used
to coagulate vessels. e rst commercial electrosurgical device is credited
to William T. Bovie and used for the rst time in 1926 in Boston. It uses a
generator to create high-frequency current (200 kHz) in order to prevent
nerve conduction and generate local thermal energy while at the same time
preventing remote electrical injury. Because of this, a local thermoablative
zone is created. ere are dierent modes that monopolar electrocautery
can be used. “Cut” causes a high enough voltage (>
400 V peak to peak) to
create a vapor pocket and results in an incision. It typically uses a modu-
lated periodic sine waveform. When the system is operating in “coag mode,”
the voltage output is usually lower than in the cut mode and less power is
delivered. Typically, sine wave is turned on and o in a rapid succession.
is therefore generates less heat, and a vapor pocket is not generated.
e overall eect is a slower heating process that causes tissue to coagu-
late and smaller vessels are destroyed and sealed, stopping capillary and
small arterial bleeding. In simple coagulation/cutting mode machines, the
lower-voltage cycle typical of coagulation mode is usually heard as a lower
frequency.
Monopolar electrocautery is versatile, almost universal in availability,
and cheap, acts quickly, and is relatively safe to use. It can be used in a vari-
ety of settings and can eectively help control bleeding from small vessels
and capillaries.
Limitation of Electrosurgery
Patients with electrical implants such as cardiac pacemakers require spe-
cial precautions, especially when using monopolar devices. Conventional
monopolar electrosurgery should not be used to control larger vascular
structures, around vascular compromised tissue, bowel, and other visceral
structures such as the bile duct and ureter. e limitations of monopolar
electrocautery include poor ecacy with vessels greater than 3mm, a wide
collateral zone of thermal injury, and lack of an eective feedback mecha-
nism except visual approximation.
Complications of Electrosurgery
Electrosurgery-related complications are relatively uncommon, occurring
in 2 to 5/1,000 procedures. Lack of experience and knowledge of the device’s
mechanism of action is the major contributing factor with approximately
60 procedures being the inection point for injuries from electrothermal
devices in laparoscopy.
e mechanism of electrosurgical injury includes direct injury, lat-
eral thermal spread, direct coupling, capacitive coupling, and insulation
failure. Direct coupling results from inadvertent contact of two noninsu-
lated instruments, and the current ows from the primary to the second-
ary instrument. Severe injury may result from a second conductor if it is in
contact with sensitive structures. Capacitive coupling is alternating current
owing through the primary electrosurgical device inducing unintended
stray current in any conductor (such as metal trocars of liver retractors) in
close proximity with the monopolar instrument.
Hollow viscus injury is uncommon but is often missed and can have
fatal consequences. e nature of the thermal injury is such that intraop-
eratively, the injury may be masked and will manifest usually about 4 to
10 days postoperatively, depending upon the severity of the coagulation
necrosis. In the context of liver surgery, electrocautery has caused duodenal
injury and late bile duct strictures. ese injuries can be avoided by mini-
mizing the use of electrocautery in extrahepatic pedicle control techniques.
While assessing the ecacy of the coagulation, attention should be paid
Chapter 13 / Energy Devices for Parenchymal Transection in Liver Surgery 159
to the whitening of tissue surrounding the tip of the electrosurgical instru-
ment and formation of bubbles. Whitening suggests adequate hemostasis
and bubbles represent water vapor; thus, the tissue is desiccated, and the
bubbles disappear, marking adequacy. Other visceral and vascular injuries
from electrocautery have been reported. Severe skin burns caused by a par-
tially detached grounding pad/return electrode can occur, but most mod-
ern electrosurgical monopolar devices have a return electrode monitoring
system to prevent this problem. Use of lowest-eective power settings,
intermittent activation, and direct visual feedback for adequacy are good
practices for the prevention of injury. With bipolar electrosurgery, termina-
tion at the end of the vapor phase and alternating between desiccation and
incision are a good practice.
Our preference is to use the monopolar electrosurgical device to gain
access to the abdomen and use it for mobilization of the right hepatic lobe
o the triangular ligaments. We also use it to “score” the liver capsule while
delineating resection lines. is demarcation dening the line of resection
can be seen with high-quality ultrasound imaging and helps to ensure an
adequate margin prior to resection. is line of demarcation for resection
is even more important when performing laparoscopic resections given the
limited visualization and lack of tactile feedback during resection.
Conventional Bipolar Electrosurgery
In bipolar electrosurgery, both the active electrode and return electrode
functions are performed at the site of surgery. e two tines of the forceps
perform the active and return electrode functions. Only the tissue grasped
is included in the electrical circuit. Because the return function is per-
formed by one tine of the forceps, no patient return electrode is needed.
Most bipolar units use a low-voltage waveform that achieves hemostasis
without excessive charring. For the same reasons, bipolar electrosurgical
devices are less eective for cutting tissue since adequate vaporization is
dicult to achieve. Eective hemostasis can be achieved by coapting and
thermally welding the blood vessels. Conventional bipolar is widely used in
neurosurgery and gynecologic surgery.
Bipolar electrosurgery technology is very safe because of limited
tissue conduction. Use of lower voltages in a smaller circuit leads to less
lateral thermal spread and injury. Bipolar energy is also safer to use when
there is a question about the safety of using more powerful monopolar elec-
trosurgical units (i.e., implantable medical electromagnetic devices such as
pacemaker, debrillator, pumps). ere are some disadvantages to the use
of bipolar: Bipolar cannot spark to tissue, and the low voltages make it less
eective on large vessels.
BIPOLAR VESSEL-SEALING DEVICES
Ligasure
Vessels sealing devices stemmed from renement of bipolar electrosurgery
technology. e bipolar vessel-sealing system (LigaSure) applies a precise
amount of bipolar energy and pressure to fuse collagen and elastin within
the vessel walls. is fusion is done using a feedback-controlled energy
delivery through a generator that senses adequate coaptation and coagu-
lation. In addition, the device minimizes lateral thermal spread. e seal
with this device can withstand three times the normal systolic pressure and
seals vessels up to 7mm. e sealing is achieved with minimal sticking and
charring; thermal spread to adjacent tissues is approximately 2mm. Vessel
sealing has steadily gained acceptance in various surgical disciplines due to
its ease of use and ability to seal relatively large vessels. To underscore this
Section II / Liver160
point, vessel sealing has been successfully used on the splenic hilum. e
disadvantages include the need to fully engage and lock the clamps before
delivery of energy can occur and the nonuniform compression it delivers
over the length of the prongs. is technology is fast growing with propo-
nents arguing the ease of use, fast sealing, and relative cost–benet versus
other devices. It is also one of the few devices with a cost–benet analysis
in its favor in published literature.
Ligasure has fast been gaining ground in laparoscopic surgery and
has been used extensively in colorectal and bariatric procedures. A sys-
tematic review of six randomized controlled trials of hemostatic devices
in colectomy was favorable for the use of Ligasure over conventional elec-
trosurgery but did not demonstrate clear superiority over other ultrasonic
vessel-sealing devices. A Japanese randomized control trial (RCT) demon-
strated Ligasure’s superiority with respect to blood loss, transection times,
and lower number of ties required. ey also showed a cost–benet in using
Ligasure over conventional techniques. is was however followed shortly
later by another Japanese trial showing no benet over the crush–clamp
technique. Another RCT, which showed superiority of the clamp–crush
technique, was conducted under inow control and that needs to be taken
into consideration in the era of minimally invasive surgery where inow
control is the exception rather than the norm.
EnSeal
Enseal is another vessel-sealing system that uses bipolar electrosurgical
principles. EnSeal delivers vessel sealing by using a combination of compres-
sion and thermocoagulative energy to ensure hemostasis. It is capable of
achieving seal strengths up to seven times the normal systolic pressures on
vessels up to 7mm with a typical thermal spread of approximately 1mm. It
diers from Ligasure in its compression mechanism, which applies uniform
pressure along the full length of the instrument jaw, achieving compression
forces similar to those of a linear stapler of up to 7,800psi. Compression is
combined with controlled energy delivery utilizing Nanopolar thermostats
to reach collagen denaturation temperatures in seconds: temperatures
maintained at approximately 100°C throughout the power delivery cycle.
e device also has a simultaneous cutting mechanism to allow one-step
sealing and transection of vessels and soft tissues. e big cost advantage
is the ability to use conventional bipolar generators for its use, thereby
obviating a large new capital investment for generators. EnSeal also has
a large jaw width and produces minimal smoke (or steam). e dynamic
dual mechanism mandates active operator eort and cognizance and has a
modest learning curve as compared to other lock-re devices.
is device is about 3 cm in length at the functional portion of the
head, which is comprised of jaws. e instrument head is designed to
facilitate atraumatic dissection. In a comparative porcine model, Enseal
devices were reported to achieve higher burst pressures with a sub-mm lat-
eral thermal spread. Another ex vivo study reported longer sealing times
and variable burst pressures with Enseal as compared to Ligasure device.
ere have been few clinical studies of Enseal in published literature and
no randomized controlled trials. Initial studies demonstrated the safety
prole of this device. A single-center study on laparoscopic liver resection
using the EnSeal versus ultrasonic dissector showed shorter parenchymal
transection time. However, head-to-head comparisons with conventional
clamp–crush are not available in current literature. Despite this paucity
of clinical data, its performance in preclinical studies, ease of use, and
ability to simultaneously seal and divide large vessels without signicant
lateral thermal spread have made Enseal popular among many centers.