Figure 52-8. 3D CT reconstructions of (A) Normal arterial supply to the pancreas, (B) Replaced right hepatic artery arising from

the superior mesenteric artery, (C) Replaced common hepatic artery arising from the superior mesenteric artery and (D) Replaced

left hepatic artery arising from the splenic artery.

Variations or anomalies in the pancreatic and biliary blood supply are found in 20% to 30% of people.

In most cases, all or part of the hepatic arterial blood supply does not arise from the celiac axis. As

much of the pancreatic blood supply is derived from the hepatic arterial blood supply, these variations

lead to variations in the pancreatic blood supply. In approximately 20% of patients, the replaced right

hepatic artery arises from the superior mesenteric artery (Fig. 52-8B) in the retropancreatic position and

traverses the upper edge of the uncinate process, then runs posterolateral to the portal vein. In this case,

a pulse remains in the hepatoduodenal ligament and the gastroduodenal artery can arise from the

replaced right or the left hepatic artery. The right hepatic artery can also originate from the right

gastric in 2% of cases or from the gastroduodenal artery in 6% of cases.

The entire hepatic arterial supply can be replaced, with the common hepatic artery originating from

the SMA instead of the celiac axis (Fig. 52-8C). In this case, there is no hepatic arterial pulse medially in

the hepatoduodenal ligament. The replaced common hepatic artery runs anterior to the portal vein, but

posterior to the bile duct and gives rise to a gastroduodenal branch, which is also posterior to the bile

duct. In approximately 10% of cases, the left hepatic artery can be aberrant, most commonly arising

from the left gastric artery instead of the proper hepatic artery.

Venous Drainage

The venous drainage of the pancreas follows the arterial blood supply and is eventually returned to the

portal circulation and delivered back to the liver. There are four main routes of venous drainage in the

pancreas. In the pancreatic head the superior venous arcades drain either directly into the portal vein

superiorly or laterally. The anterior and inferior pancreaticoduodenal arcades drain directly into the

infrapancreatic SMV. There are rarely any anterior branches from the pancreatic head and neck into the

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superior mesenteric and portal veins. When they do occur, it is most commonly at the superior border

of the pancreatic neck.

The body and tail of the pancreas has many venous tributaries that drain into the splenic vein, which

joins the SMV posterior to the pancreatic neck forming the portal vein (PV). The three named

tributaries of the splenic are the inferior pancreatic vein, the caudal pancreatic vein, and the great

pancreatic vein. The inferior mesenteric vein (IMV) does not drain the pancreas, but joins the splenic

vein posterior to the pancreatic body. The PV then drains the intestinal blood supply to the liver.

Lymphatic Drainage

Throughout the pancreas there is a rich periacinar network of lymphatic vessels which drain to five

major nodal groups: superior, inferior, anterior, posterior, and splenic.40 The superior nodal group runs

along the superior border of the pancreas and celiac trunk. They drain the superior portion of the

pancreatic head. The inferior nodal group along the inferior border of the head and body of the

pancreas drain the inferior pancreatic head and uncinate process, eventually draining to the superior

mesenteric and paraaortic lymph nodes. The anterior lymphatics drain to the prepyloric and infrapyloric

nodes. The posterior lymph nodes include the distal common bile duct and ampullary lymphatics and

drain directly into the paraaortic lymph nodes. Finally, the splenic lymph nodes drain the lymphatics of

the pancreatic body and tail into the interceliomesenteric lymph nodes.

The Japanese Pancreas Society has classified the pancreatic lymphatic drainage into 18 lymph node

stations (Table 52-5).42 The greater and lesser curves of the stomach drain into lymph node stations 1

through 4. The anterior lymphatics described above drain into lymph node stations 5 and 6. The

superior nodal group includes lymph node stations 7 through 9 along the left gastric artery, common

hepatic artery, and celiac axis. The posterior lymph nodes include lymph node stations 12 (and all

subdivisions) and 13, while the inferior nodal group comprises stations 14 through 17. The splenic

lymph node group corresponds to Japanese lymph node stations 10 and 11.

Innervation

The innervation to the pancreas is derived from the vagus and thoracic splanchnic nerves as well as

peptidergic neurons that secrete amines and peptides.43 Parasympathetic and sympathetic fibers for

ganglia along the celiac axis and superior mesenteric artery, which give rise to the pancreatic branches

reach the pancreas by passing along the arteries from the celiac axis and superior mesenteric arteries.

The parasympathetic nerves stimulate both exocrine and endocrine secretion, while the sympathetic

fibers have a predominantly inhibitory effect (Fig. 52-9).44 The peptidergic neurons secrete hormones

including somatostatin, VIP, calcitonin gene–related peptide (CGRP), and galanin. While the peptidergic

neurons influence exocrine and endocrine secretion, their precise physiologic role is unclear. The

pancreas also has a rich network of afferent sensory fibers.

Table 52-5 Japanese Lymph Node Stations

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SURGICAL SIGNIFICANCE OF PANCREATIC ANATOMY

10 Knowledge of the anatomy and anatomical variants can give clues to the diagnosis of pancreatic

disease based on signs and symptoms. In addition, an understanding of the pancreatic anatomy in

relation to adjacent structures is essential when performing operative procedures on the pancreas or

surrounding structures including the duodenum, bile duct, and spleen.

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Figure 52-9. Schematic diagram of the neurohormonal control of the exocrine cells. Visceral receptors line the ductule system and

carry the sensation of pain to the spinal cord. Sympathetic fibers first synapse in the celiac plexus after traveling through the

thoracic ganglia and splanchnic nerves. Postganglionic fibers then synapse on intrapancreatic arterioles. Parasympathetic

preganglionic fibers travel through the celiac plexus after leaving the vagus nerves and course with vessels and ducts to synapse on

postganglionic fibers near acinar cells, islet cells, and smooth muscle cells of major ducts. Stimulation of these parasympathetic

fibers results in an immediate release of pancreatic enzymes. Secretin and CCK first enter the pancreas through the capillary

network of the islet cells, and then enter the separate capillary network of the acinar tissue through the insuloacinar portal vessels.

Glucagon, somatostatin, pancreatic polypeptide, and insulin from the islets cells reach the acinar tissue immediately after release.

In this way, the islet cells can influence the acinar tissue responses to CCK and secretin.

Pancreatic Anatomy and Pancreatic Cancer

Approximately, 75% of pancreatic adenocarcinomas occur in the pancreatic head at the genu of the

pancreatic duct.45 As a result, people who develop cancer in the head of the pancreas most commonly

present with obstructive jaundice secondary to occlusion of the intrapancreatic bile duct by tumor,

leading to earlier diagnosis. People with body and tail tumors present with abdominal pain and other

vague abdominal symptoms, often leading to a delay in diagnosis. Nearly 85% of resected pancreatic

tumors are in the head, neck, or uncinate process of the pancreas.46

Similarly, patients with cancer in the pancreatic head often have invasion of the adjacent duodenum.

They may present with or develop signs and symptoms of duodenal or gastric outlet obstruction. In

patients with unresectable disease, late gastric outlet obstruction in patients requiring

gastrojejunostomy or duodenal stenting occurs in 10% to 20% of patients. A prospective, randomized

trial demonstrated that the addition of prophylactic gastrojejunostomy in addition to

hepaticojejunostomy significantly reduced gastric outlet obstruction in patients with unresectable

disease undergoing open biliary bypass.47 However, in the modern era, biliary stenting is so effective

that operative hepaticojejunostomy for unresectable disease is rarely indicated. In the setting of isolated

gastric outlet obstruction in unresectable disease, duodenal stenting is an option. When successful this

can avoid surgery and its negative impact on the remaining quality of life. In a meta-analysis of trials

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comparing endoscopic stenting to gastrojejunostomy, stenting was associated with shorter time to oral

intake and shorter length of stay, with similar complication rates, and decreased mortality.48

11 The ability to resect a pancreatic cancer depends on the presence or absence of metastatic disease

and the extent of local vascular involvement. Pancreatic cancers are classified as resectable, borderline

resectable, or unresectable (including locally advanced unresectable disease and metastatic disease).

Table 52-6 shows the 2014 National Comprehensive Cancer Network definitions for resectable,

borderline resectable, and unresectable disease.49 Tumors are considered resectable if they have: (1) no

distant metastases, (2) no radiographic evidence of SMV or PV distortion, and (3) clear fat planes

around the celiac axis, hepatic artery, and SMA (Fig. 52-10A).

Table 52-6 Criteria for Resectability in Pancreatic Cancer

Tumors are considered borderline resectable if they have: (1) no distant metastases, (2) venous

involvement of the SMV or PV with distortion or narrowing of the vein or occlusion of the vein with

suitable vessel proximal and distal, allowing for safe resection and replacement, (3) gastroduodenal

artery encasement up to the hepatic artery with either short segment encasement or direct abutment of

the hepatic artery, without extension to the celiac axis, and (4) tumor abutment of the SMA not to

exceed greater than 180 degrees of the circumference of the vessel wall (Fig. 52-10B).

Tumors are considered to be locally unresectable if there is: (1) no distant metastatic disease, (2)

greater than 180 degrees SMA encasement, (3) any celiac axis abutment, (4) unreconstructable

SMV/portal occlusion, (5) invasion or encasement of the aorta or inferior vena cava (IVC), and (6)

nodal involvement outside the field of resection. Patients with any distant metastatic disease, most

commonly to the liver or lymph nodes outside the field of resection, or the presence of peritoneal

carcinomatosis are considered unresectable.

Pancreatic head cancers may also involve adjacent organs including the hepatic flexure of the colon,

the gallbladder, or the stomach. If there are no distant metastases, resection of these organs en bloc is

indicated. For cancers in the body and tail without distant metastasis, involvement of the splenic artery

and/or vein does not preclude resection as these vessels are normally taken during the operation.

However, involvement of the celiac axis or superior mesenteric artery precludes resection. Involvement

of adjacent organs including the left kidney, left adrenal, spleen, and left colon can be resected if

involved with tumor and there is no distant disease.

Knowledge of the normal pancreatic blood supply is critical in order to perform an adequate cancer

operation. As the duodenum and head of pancreas share a blood supply, it is necessary to remove these

organs en bloc when performing an operation for carcinoma. While the duodenum can be preserved in

resections performed for benign disease (duodenum-preserving pancreatic head resection), this is not

the case in patients with cancer. Likewise, for cancers in the body and tail of the pancreas it is necessary

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to resect the spleen and its blood supply since it shares a blood supply with the tail of the pancreas. For

benign diseases of the pancreatic tail, the spleen can be preserved.

There has been significant debate regarding the extent of lymph node dissection necessary in patients

undergoing curative resection for pancreatic cancer. Table 52-5 shows the difference in extent of

lymphadenectomy between the standard and radical procedure. The standard procedure includes the

bile duct (station 12b2) and cystic duct lymph nodes (station 12c), the posterior (station 13) and

anterior (station 17) pancreaticoduodenal lymph nodes, the SMV nodes (station 14v), and the nodes on

the right side of the superior mesenteric artery (station 14b). Radical resection adds a distal

gastrectomy (stations 3, 4, 5, and 6) and a retroperitoneal dissection extending from the right renal

hilum to the left lateral border of the aorta horizontally with samples of celiac nodes, and from the

portal vein to below the third portion of the duodenum vertically (lymph node stations 16a1, 16b2, and

9). In the United States, standard resection is most commonly performed.

Figure 52-10. A: Resectable pancreatic head cancer. There is a clear plane between the tumor and both the superior mesenteric

artery and superior mesenteric vein. B: Borderline resectable pancreatic cancer. Involvement of the superior mesenteric vein with

distortion and narrowing; tumor abutment of the superior mesenteric artery less than 80 degrees of the circumference.

Awareness of the common anatomic variants in biliary and pancreatic arterial supply is necessary to

prevent major vascular injury and damage to the hepatic blood supply during pancreatic resection. The

gastroduodenal artery is the largest named artery taken during pancreaticoduodenectomy. In the case of

a replaced right hepatic artery arising from the superior mesenteric artery, the gastroduodenal artery

can arise from this replaced vessel and enter the pancreas posterior to the bile duct. In addition, this

replaced right hepatic artery courses to the liver lateral to the bile duct and can easily be injured during

dissection of the pancreatic uncinate process off of the superior mesenteric vessels. A replaced right

hepatic artery often supplies the entire right lobe of the liver causing significant hepatic ischemia if

injured. In the case of a replaced right hepatic artery, there will still be a pulse medially in the

hepatoduodenal ligament from the left hepatic artery, but this will supply only the left lobe of the liver.

In the case of a replaced common hepatic artery, the entire hepatic blood supply will be from the

SMA. There will be no pulse medially in the hepatoduodenal ligament. The replaced vessel will again be

posterior and lateral to the bile duct and at risk of injury if not correctly identified. Given the closer

proximity of the replaced vessels to the pancreatic head and uncinate process, these replaced vessels

may also be more prone to direct involvement by tumor. If injured or involved with tumor and

resected, these often require reconstruction to restore adequate hepatic blood supply.

Due to the rich afferent sensory fiber network within the pancreas, abdominal pain and back pain are

common presenting symptoms in patients with pancreatic cancer. As pancreatic cancer progresses, the

nervous plexuses along the celiac axis in the retroperitoneum can be invaded by a tumor causing the

characteristic intractable back pain. In this setting, celiac ganglion blockade (sympathectomy) or

neurolysis using alcohol can provide significant pain relief by interrupting these somatic fibers. A celiac

block can be performed endoscopically,50 percutaneously, or intraoperatively. Endoscopic ultrasound

(EUS)- or CT-guided celiac plexus neurolysis should be considered first-line therapy in patients with pain

secondary to unresectable, locally advanced pancreatic cancer.51 Celiac blockade has been shown to

reduce pain in patients with unresectable pancreatic cancer undergoing operative bypass procedures for

obstructive jaundice and duodenal obstruction.52,53

Pancreatic Anatomy and Pancreatitis

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