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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_585_Библиотеки_им_академика_М_И_Перельмана.pdf
12
J. Ouyang et al.
the corresponding function icons of the display window,
transparency (a value of 0 means completely transparent,
a value of 1 means completely opaque, and values
between 0 and 1 are semitransparent) and color of each
part can be adjusted, and thus the liver can be displayed
Fig. 1.14 A 3D reconstructed
model of the liver and its
internal structure. (a)
Structure of the liver and its
internal pipelines (liver
translucent, other opaque); (b)
Structure of the liver and its
internal pipelines (Back view)
(semitransparent liver,
transparent liver veins)
and observed as needed. The liver model can be rotated
by holding down the left mouse button and dragging laterally. The viewer can zoom in or out of the image by
right clicking the mouse and dragging up or down
(Fig.1.14).
a
b
1 Applied Anatomy oftheBiliary Tract
13
Data for 3D reconstruction of the intrahepatic vessels
were mostly obtained from CT, MRI, and ultrasound; however, information collected by these instruments was incomplete or insufcient. Using these data for 3D reconstruction
of the liver would lead to inevitable defects (Spitzer and
Whitlock 1998). However, after perfusion and casting of
intrahepatic vessels applying the advanced casting technology, an image dataset of the liver section could be obtained
through a serial section of the liver at 0.2mm intervals with
a milling machine. These images contained detailed information of intrahepatic vessels. The image sequences were
registered, segmented, and subsequently reconstructed using
the VTK (William etal. 2000). After registration and segmentation of these images, VTK was used to establish threedimensional surface morphological models of hepatic veins
and inferior vena cava, hepatic artery, portal vein, bile duct,
and gallbladder, respectively. By setting the color and transparency of each pipe structure and zooming-in, zoomingout, and rotating the model, it is possible to accurately and
comprehensively observe and study the morphology and
adjacent relationship of the liver and its various structures,
which provides an excellent technical platform for teaching
and further researching the anatomy of the intrahepatic biliary tract.
References
Couinaud C.Surgical anatomy of the liver revisited Ch4. Anatomy of
the dorsal sector of the liver. New considerations on liver anatomy.
Paris: Pers ED; 1989. p.26–39.
Fang C, Yang J, Fan Y, et al. The research of virtual hepatectomy.
Chinese J Surg. 2007;45(11):753–5.
Hjortsj CH.The topography of the intrahepatic duct system. Acta Anat
(Basel). 1951;11:599–615.
Kogure K, Kuwano H, Fujimaki N, etal. Relation among portal seg-
mentation, proper hepatic vein, and external notch of the caudate
lobe in the human liver. Ann Surg. 2000;231(2):223–8.
Misra SP, Dwivedi M. Pancreaticobiliary ductal union. Gut.
1990;31:1144–9.
Ramesh Babu CS, Sharma M.Biliary tract anatomy and its relation-
ship with venous drainage. J Clin Exp Hepatol. 2014;4(Suppl
1):S18–26.
Spitzer VM, Whitlock DG.The visible human Dataset: the anatomical
platform for human simulation. Anat Rec. 1998;253(2):49–57.
Spitzer VM, AcKerman MJ, Scherzinger AL, et al. The vis-
ible human male: a technical report. J Am Med Inform Assoc.
1996;3(2):118–30.
Wigmore SJ, Redhead DN, Yan XJ, etal. Virtual hepatic resection using
three-dimensional reconstruction of helical computed tomography
angioportograms. Ann Surg. 2001;233(2):221–6.
William JS, Kenneth MM, Lisa SA, et al. The VTK user’s guide.
NewYork: Kitware; 2000.
Zhong S. Applied clinical anatomy[M]. Beijing: People’s Military
Medical Press; 1998. p.355–6.
Application ofMulti-slice Spiral CT
andMRI inBiliary Surgery
SuishengZheng, XijunGong, XuchangZhang,
YangguangYuan, XinmingLi, andChihuaFang
2
2.1 Introduction
Multi-slice computed tomography (CT) and Magnetic
Resonance Imaging (MRI) each offers unique methods of
viewing internal structures, diseased tissue, and deposits
such as calculi.
This chapter will present:
• Basic principles of Multi-slice CT
• Patient preparation and scanning modalities
• Clinical application to biliary system investigations
• Basic principle of MRI
• MRI patient preparation and scanning modalities
• MRI in biliary surgery
2.2 Application ofMulti-slice Spiral CT
inBiliary Surgery
2.2.1 Basic Principles
Computed tomography (CT) scan is an imaging technology
that uses a series of X-rays to build cross-sectional images of
the body. The emitter of X-rays rapidly rotates around the
patient, and the detector in the scanner picks up the images
of a body section and measures the differences between the
X-rays that are absorbed by and transmitted through the
body, which is called attenuation. Different tissues each have
a different attenuation coefcient. The signal transmitted by
the detector is in analog form, and it must be subsequently
converted into digital form by an analog/digital converter
before it can be sent to a PC for processing. These digital
S. Zheng · X. Gong
The Second Afliated Hospital of Anhui Medical University,
Anhui, China
X. Zhang · Y. Yuan · X. Li · C. Fang (
Zhujiang Hospital, Southern Medical University,
Guangzhou, China
*)
signals are the sum of the attenuation coefcients. Digital 3D
images are divided into small equal-sized polygons, and the
polygons in three-dimensional space are called voxels
(Fig.2.1). The X-ray attenuation or absorption coefcient is
obtained and then arranged into a matrix, which is called the
digital matrix. The value of each digit in the matrix is converted into different gray levels. They are subsequently converted into pixels. Thus, a grayscale CT image is generated
(Miller etal. 2014).
Multi-slice spiral CT (MSCT) is the further development
of single-slice spiral CT based on slip-ring technology. The
slip-ring mechanism involves electric slip-ring devices composed of two parts, a stator, and two concentric rotors. The
slip ring is installed in the stationary part, while the xed
brush in the rotatable part. The xed brush makes sliding
contact with the conductor ring, and the X-ray tube is energized through the brush and slip-ring by the power supply
system. Therefore, the X-ray tube can rotate continuously at
high speed during data acquisition. The path of a full cone
X-ray emitted from the tube of MSCT presents a helical trajectory relative to the patient. During the acquisition of volume CT data, the patient is continuously moved through the
gantry as the X-ray tube rotates Since the X-ray tube rotates
continuously around the patients with a helical movement,
the scanning speed is signicantly enhanced. The increase in
the scanning speed and width of detector coverage can
reduce the scanning time. In the obtained matrix, a threedimensional geometry is formed by the x, y, and z-axes. The
obtained information is produced from the volumetric data
set within a specic range (Goldman 2008). The reconstructed organ image is three-dimensional and allows for
360° rotation and cross-section observations. Meanwhile,
the increase in scanning speed can yield dynamic scanning
and observation of organ images.
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
C. Fang, W. Y. Lau (eds.), Biliary Tract Surgery, https://doi.org/10.1007/978-981-33-6769-2_2
15
16
Fig. 2.1 Voxel, pixel, and
digital matrix
S. Zheng et al.
2.2.2 Techniques andClinical Applications
ofMSCT forBiliary Imaging
2.2.2.1 Methods
Preparation
Patients are instructed to fast for 4–8h before CT examination. In order to avoid high-density artifact interference, CT
should not be performed within 72 h of a barium meal.
Abdominal uoroscopy should be performed before
examination. Barium sulfate or drugs that affect the
absorption of X-rays should be drained as much as possible
if they are found remaining in the colon. Thirty minutes
before the examination, 500–800 ml of a 1.5%–3.0%
iodinated contrast agent or water should be administered
orally; an additional 400 ml of contrast agent should be
administered immediately before the examination.
Positioning the patient in the right lateral decubitus position
for 5min is sometimes necessary to ll the duodenum and
the proximal small intestine, which is benecial to show the
relationship of the duodenum to the head of the pancreas and
the lower end of the common bile duct. When
choledocholithiasis is suspected, water shall be taken instead
of a contrast agent, so as not to confuse gallstones with
contrast agent in the duodenal diverticulum. If the focus of
observation is the lower common bile duct and ampulla, an
anticholinergic drug such as anisodamine-2 (654–2) can be
administered intramuscularly 15 min prior to the scan to
achieve low tension of gastrointestinal tract, full dilation of
the duodenum, and reduction of peristalsis artifacts. In such
cases, the anatomical structure of the lower common bile
duct and ampulla can be better displayed, and so can the
lesions. It is critical to instruct patients to hold their breath
under the condition of calm breathing before the examination
and to remove foreign objects that affect X-ray attenuation at
the site of the examination. These steps are essential for
precise diagnoses.
Selection ofScanning Parameters
The selection of scanning parameters includes three aspects:
collimator width, pitch, and reconstruction interval.
Collimation width determines the slice thickness of the scan
layer, most of which are set as 3–5m. Pitch refers to the
distance that the patient travels through the CT scanner per
360° rotation of the X-ray tube, divided by the beam
collimation width. Alternatively, the pitch can be replaced by
table speed. Meanwhile, collimation width determines the
thickness of the reconstruction slice. Narrowing the
collimation width can reduce the photon density of the layer
and improve the resolution, but it is challenging to cover the
full scanning range. The scanning range can be enlarged by
increasing the collimation width though this will reduce the
special resolution. The spatial resolution of the postprocessed image is determined by the reconstruction interval,
and most of the recombination intervals of images should be
less than 1mm.
2 Application ofMulti-slice Spiral CT andMRI inBiliary Surgery
17
Scanning Modalities
Axial Plain Scanning Axial plain scanning of the biliary
system is performed as part of a routine clinical examination.
The patient should be in a supine position, and the scan range
extends from the top of the diaphragm to the lower edge of
the liver. The patient breathes calmly and holds the breath
while exposed. Continuous scan with a thickness of 5mm
and a thin-slice scan of the region of interest (ROI) in small
lesions should be performed. The scan range usually includes
the entire liver, and the range of biliary system ranges from
the top of the liver to the uncinate process of the pancreatic
head. The range should be adjusted according to the patient’s
clinical status. When thickening of the gallbladder and bile
duct wall or an intraluminal soft tissue mass are detected, a
contrast-enhanced CT scan is necessary. It enhances the
contrast between the bile duct and the surrounding tissues
and clearly shows the stereoscopic anatomy of the biliary
system, which is convenient for evaluating causes of biliary
obstruction and the degree of tumor invasion.
Contrast-Enhanced Scanning
Principles and Signicance of Contrast-Enhanced
CT
Enhanced scanning can better display the iso-dense
lesions, observe the blood supply of the lesions, and identify
the nature of the lesions. Principles of contrast agents: Watersoluble iodinated contrast agent that is intravenously administered weakly or rarely binds to the human protein, and
instead, it is distributed in large quantities in the blood vessels, then owing into the extracellular uid of various tissues and gradually reaching equilibrium. The enhancement
of normal and diseased tissues is caused by the increase in
the amount of iodine, increasing local density. The amount
of contrast agent distributed in a specic tissue depends on
the volume and velocity of blood ow, microvascular permeability, and the volume of the extracellular uid of this tissue.
The effect of enhancement is related to the concentration and
injection method of the contrast agents; it is also associated
with whether the scanning time is synchronized with the
time to peak enhancement in the tissue.
Enhanced scanning plays a signicant role in diagnostic
techniques. The fundamental purpose of using contrast
agents is to enhance the contrast between the intrahepatic
and extrahepatic biliary lesions and normal tissues through
contrast enhancement, thus achieving a clear display of
lesions. Some lesions are not clearly displayed or show an
ambiguous boundary on the plain scan. Rich vascularized
lesions can be displayed after enhancement; poorly
vascularized lesions exhibit poor enhancement, while
adjacent normal tissues are enhanced; thus, increasing the
detection rate. The application of contrast-enhancing agents
plays an essential role in the localization, qualitative analysis,
and differential diagnosis of lesions. Contrast-enhanced
scanning not only provides qualitative information through
the degree of enhancement of diseased tissue, but also clearly
shows the blood vessels at the porta hepatis, which helps
evaluate the nature of biliary lesions in this area. For
malignant lesions, the resection rate can be determined
according to vascular involvement. At the same time, the
liver parenchyma is signicantly enhanced during the portal
venous phase, which is benecial for the detection of
intrahepatic bile duct neoplastic lesions, biliary tract tumors,
and hepatic metastases.
Contrast-Enhanced Examination
• Typically, the water-soluble iodinated contrast agent is
administered by rapid bolus intravenous injection. The
usual dose for bolus injection is 1.0–2.0 ml/kg at an
injection rate of 3ml/s. Triple-phase scanning is generally
adopted: the timing of the delay is synchronized with the
start of injection. The arterial phase scan is triggered by
the threshold triggering protocol or starts at a delay of
20–30s. The portal venous and equilibrium phases start at
a delay of 60–70s and 2–3min, respectively. Observation
of the extrahepatic bile duct should start from the
bifurcation of the left and right hepatic ducts, the
pancreatic head, to the continuous thin layer of third and
fourth segments of the duodenum.
• Dynamic Enhanced Scanning After the bolus injection of
contrast agents, the lesions or the whole biliary system are
scanned continuously at different times to observe the
time–density curve of lesion enhancement. The dynamic
enhanced scan can obtain more information on the blood
supply of the lesions, compared with conventional triplephase scanning, which is of great signicance for
differential diagnosis.
• CT Angiography CT angiography is an examination that
displays biliary lesions, especially the condition of the
arterial blood supply of rich vascularized lesions and
adjacent portal veins. It should be performed by multislice CT, and fast bolus injection should be adopted. The
thickness of the reconstruction slice should be below
1.0 mm. After the acquisition of images at enhanced
arterial and venous phases; image post-processing
software should be used to display the relationship
between specic arterial or venous vessels as well as
blood vessels and their surrounding tissues and lesions.
2.2.2.2 Post-Processing Techniques forMSCT
Volume data can be processed by a variety of post-processing techniques, including image editing and three-dimensional (3D) processing. There are four methods for the
reconstruction of spiral CT:
18
S. Zheng et al.
Shaded Surface Display
Shaded Surface Display (SSD) is a process of surfacerendering and reconstruction that connects all pixels with a
given value higher than a certain threshold to form a surface
model. The rst step is the calculation of the normalized CT
value at the surface points for 3D surface reconstruction.
Pixels above the threshold are assigned to the iso-density,
while the pixels below this threshold are discarded. Through
computer processing, the pixels above the threshold are
reconstructed into an independent three-dimensional
structural model. This method is of great value in displaying
the whole lesion, and its advantage is that the image has a
strong stereoscopic effect, which accords with human visual
cognition. The disadvantage is that the selection of the
threshold has an essential inuence on the recombination
effect, and the display of the smaller bile duct is easily
affected by the partial volume effect.
Maximum Intensity Projection
Maximum Intensity Projection (MIP) is a volume rendering
technique that generates 2D images from volumetric data
along with the mathematical rays. It encodes and recombines
the highest density value encountered along the viewing ray.
This technique is mostly used in the recombination of the
biliary system after enhancement, with the advantages of
displaying biliary system structure in multiple directions and
angles, and relatively easy operation. However, the limitation
of this technique includes the inability to show superimposed
objects, which can be addressed by segmentation techniques.
Multi-Planar Reconstruction andCurved Planar
Reformation
Multi-planar Reconstruction (MRP) involves the process
reformatting of a 3D data set acquired from volume scanning
into a three-dimensional reconstruction of sagittal, coronal,
and oblique anatomical planes. Curved Planar Reformation
(CPR) involves generating 2D images that are reconstructed
in arbitrary planes from axial image data. Both of these
methods produce two-dimensional images, which are not
conducive to displaying the overall anatomical structure.
Nevertheless, they are fast and straightforward, and CPR can
completely display the structure of the biliary tree.
Volume Rendering
A Volume Rendering (VR) process involves calculating the
percentage of substances in each pixel by a computer system
and displaying them as grayscales. Different brightness
levels are assigned accordingly, and the contrast between
tissues can be adjusted as needed. VR is one of the most
commonly used methods for the vascular reconstruction of
the porta hepatis. It cannot only display anatomical structures
with different tissue density, but the structure of the lumen
and its relationship with surrounding structures (Flohr and
Ohnesorge 2007).
2.2.3 Application ofCT totheBiliary System
2.2.3.1 For Bile Duct Stones andBiliary Tract
Inammation
CT scanning has the advantages of high speed, rapid imaging, small artifacts, and high resolution. Some patients with
bile duct stones have an acute onset, which can be diagnosed
accurately and timely by the CT examination. CT can also
detect the location of bile duct stones and associated biliary
dilatation and inammatory lesions. Thus, it is widely used
in clinical practice. Because of its nature, it has a high
diagnosis rate for high-density stones. However, its
identication of iso-density or slightly low-density stones is
insufcient due to the fact that it is easily affected by partial
volume effect, and if dilatation of the common bile duct
occurs, misdiagnosis can easily happen. Also, its clinical use
is limited due to its low sensitivity to the diagnosis of silt-like
and iso-density stones. CT examination can show the
distribution of intrahepatic bile duct stones and the dilatation
of the duct system; meanwhile, it can evaluate the atrophy of
hepatic parenchyma or associated tumor, the presence or
absence of hypertrophy in the liver lobe, splenomegaly
caused by secondary cholestatic cirrhosis and portal
hypertension, and esophageal varices. However, CT scans
create two-dimensional cross-sectional images, incapable of
further revealing the relationship between hepatolithiasis,
bile duct stenosis, and adjacent tissue structures, especially
for silt-like stones and negative stones, reconstruction and
careful selection should be performed based on the original
thin-slice data.
For biliary inammatory lesions and liver lesions compli-
cated by gallstones, abnormal enhancement of the bile duct
wall and liver parenchyma can be found by plain and contrast-enhanced CT scans. For diagnosis and differential diagnosis of congenital lesions such as biliary tract variations,
contrast-enhanced CT scans can be signicant on the premise
that enhancement of liver parenchymal phase can be accurately grasped, in combination with three-dimensional reconstruction of the biliary tract.
2.2.3.2 For Diagnosis ofTumor andBiliary
Obstruction
With the advancement of CT technology, MSCT scans in a
wide range. The application of MPR and CPR for cholangiopancreatography can clearly show the cholangiopancreatic
structure and anatomical relationship between the lesion and
surrounding tissues. It can also identify the cause of obstruction, improve the diagnosis rate of biliary obstruction, and
provide more imaging evidence for the diagnosis of biliary
obstruction in the aspects of location, course of disease development, and complications. It provides strong technical support for the clinical selection of appropriate treatment. MSCT
is a mature and commonly used imaging method for clinical
diagnosis of hilar cholangiocarcinoma. By using this tech-
2 Application ofMulti-slice Spiral CT andMRI inBiliary Surgery
nique, the extent of the dilatation of proximal bile duct and
the location of biliary obstruction are displayed; meanwhile,
it reveals the shape and thickness of the bile duct wall, as well
as the size and boundary of the tumor; it also indicates
whether there is abdominal metastasis. Also, compared with
ultrasound, this method is not affected by factors such as
intestinal gas, obesity, and examiners. In this way, the accuracy of an examination is improved. The advantage of MSCT
lies in its powerful post-processing function, such as MPR or
CPR technique, which can improve the image resolution and
clearly show the location of lesions and condition of the biliary tract.
2.2.3.3 For Display oftheBlood Supply
oftheBiliary System
The intrahepatic bile duct and common bile duct have a copious blood supply after entering the pancreatic parenchyma
and duodenal wall. Slender arteries have less surgical signicance. Therefore, the biliary vessels refer to the arterioles
supplying the extrahepatic and pancreatic bile ducts. The
cystic artery typically originates from the right hepatic artery
within the Calot’s triangle. When approaching the gallbladder, the cystic artery bifurcates into anterior and posterior
branches at the neck of the gallbladder. Variations in cystic
artery anatomy are mainly manifested in three aspects: number, origin, and course. Besides the normal trunk type, double trunk or nonclassical branch types may also appear. The
cystic artery typically originates from the right hepatic artery,
sometimes from the left hepatic artery, the middle hepatic
artery, the hepatic artery proper, the gastroduodenal artery, or
the superior mesenteric artery. The cystic artery may also
arise from the front of or behind the common hepatic and
bile ducts, and it may pass down below the cystic duct.
Variations in the right hepatic artery are common, so cystic
arteries originating from differing hepatic arteries will have a
concomitant structure. The blood supply of the common bile
duct is copious and complex, and the blood supplying arterioles are thin. The extrahepatic bile ducts are roughly divided
into the upper and lower portions (Fig.2.2). The upper part
of the bile duct involves the common bile duct above the
upper edge of the duodenum and the lower part of the common hepatic duct. The lower part of the bile duct includes the
upper edge of the duodenum to the upper edge of the pancreatic head, including the retroduodenal part of the common
bile duct and the pancreatic part of the common bile duct,
which has not yet entered the pancreatic parenchyma.
CT observation of extrahepatic and pancreatic bile duct
rarely showed any variation, and there is no specic route or
conuence. There were also few gross vascular features such
as the right hepatic artery arising from the gastroduodenal
artery (Fig.2.3) and the right hepatic artery/common hepatic
artery from the superior mesenteric artery (Fig.2.4).
19
Fig. 2.2 Structure of the common bile duct
Fig. 2.3 The right hepatic artery arising from the gastroduodenal
artery
Blood Supply totheLower Part oftheCommon
BileDuct
The blood supply to the lower part of the common bile duct
can be divided into 3 types according to the origin of
arterioles:
• Type I Supplied by the superior pancreaticoduodenal
arteries. According to their arterial arch anastomosis, this
type is divided into two subtypes: type Ia and Ib. In type
Ia, there are no visible anastomotic arcades between the
20
S. Zheng et al.
Fig. 2.4 The right hepatic artery (RHA)/common hepatic artery from the superior mesenteric artery (SMA)
superior pancreaticoduodenal arteries and inferior small
arteries, while in type Ib arterial arcades are formed.
• Type II Supplied by other arterioles.
• Type III No denitive supply of arterioles.
Blood Supply totheUpper Part oftheCommon
BileDuct
The enhancement rate of arterioles supplying the upper part
of the common bile duct is not high. Half of them are not
displayed, and among those that are, about half is in the
Type I is common, accounting for approximately 85%.
The superior pancreaticoduodenal artery travels in a
relatively xed direction. It usually arises after branching off
from the gastroduodenal artery, hooks around the common
bile duct, and goes toward the lower right. Type Ia is relatively
common, mainly accompanying the lower part of the common bile duct (Fig.2.5a–c).
Type I b is relatively rare. It can be observed that the superior pancreaticoduodenal artery and inferior pancreaticoduodenal artery are anastomosed into a small arterial arch. It
accompanies the lower part of the common bile duct and the
head of the pancreas (Fig.2.6). Type II (Fig.2.7) and type III
(Fig.2.8).
proximal portion of the cystic artery (Fig.2.9), and the other
half originates from the right hepatic artery (Fig.2.10). Very
few blood supply arterioles arise from the hepatic artery
proper (Fig.2.11), common hepatic artery (Fig.2.12), or left
hepatic artery (Fig.2.13).
The upper part of the bile duct is mainly supplied by the
branches of the cystic artery and hepatic artery proper, and
cases displaying the arteriole trunk are rare. The lower part
of the bile duct is mostly supplied by the superior pancreaticoduodenal artery; with a relatively high enhancement rate
and xed course, the superior pancreaticoduodenal artery
appears to be the primary arterial supply for the bile duct.
The surgeon should be vigilant when a variation of the right
ab
2 Application ofMulti-slice Spiral CT andMRI inBiliary Surgery
c
21
Fig. 2.5 (a–c) The superior pancreaticoduodenal artery accompanying the lower part if the common bile duct
Fig. 2.6 The superior pancreaticoduodenal artery and the inferior
pancreaticoduodenal artery are anastomosed into a small arterial
arch
22
S. Zheng et al.
a
b
c
Fig. 2.7 (a–c) Type II. RGEA right gastroepiploic artery, RHA right hepatic artery, LHA left hepatic artery, PHA proper hepatic artery, SMA supe-
rior mesenteric artery, CBD common bile duct
hepatic artery/common hepatic artery from the superior mesenteric artery is encountered during surgery. In the case of
insufcient exposure in the surgical eld, such as accident
injury of the right hepatic artery or common hepatic artery,
severe consequences of hepatic ischemia would occur. If a
preoperative CTA examination can be performed, the postprocessing image can better help the surgeon to perform surgery. The incidence rate of the superior pancreaticoduodenal
artery supplying the lower part of the common bile duct is
relatively high, and type I accounts for the majority. The
superior pancreaticoduodenal artery is thick and has a stable
course, which indicates that it provides a plentiful blood supply. Thus, this vascular pathway should be avoided when
choosing surgical areas. The incidence rate of type Ib is not
high. The anastomosis between the superior pancreaticoduodenal artery and the inferior pancreaticoduodenal artery is
very rare. However, if a small arterial arcade can be anastomosed, any part of the lower bile duct could be severed,
which would not cause complications such as postoperative
biliary ischemia. However, this arterial arcade is usually too
thin, which requires special care to avoid injury. The incidence rate of the proximal segment of the cystic artery sup-