BLOOD SUPPLY OF STOMACH AND DUODENUM
The conventional textbook description of the blood supply to the gastrointestinal organs and the spleen has established the misleading concept that the vascular patterns of these organs are uniform. In fact, they are unpredictable and vary in every instance. In the following account, we will first present the “typical” version of the vascular tree before examining the blood supply to each organ and then some of the common vascular variations that may be encountered in surgical resections.
Typically, the entire blood supply of the foregut organs (liver, gallbladder, stomach, duodenum, pancreas, and spleen) is derived from the celiac arterial trunk, a supplementary small portion being supplied by the superior mesenteric artery via its inferior pancreaticoduodenal branch. The caliber of the celiac arterial trunk varies from 8 to 40 mm in width. Most typically, it gives off three branches, the left gastric, common hepatic, and splenic arteries, which frequently have the appearance of a tripod (25%).
|ARTERIES OF STOMACH, LIVER, AND SPLEEN|
After branching from the celiac trunk, the left gastric artery travels superiorly and to the left. It reflects onto the cardiac region of the stomach and travels along the lesser curvature of the stomach, travelling from left to right. It also gives off an esophageal branch that ascends from the cardiac region of the stomach toward the distal esophagus.
The common hepatic artery leaves the celiac trunk and progresses to the right. In the vicinity of the portal vein it divides, sending the proper hepatic artery superiorly. The right gastric artery is also typically seen leaving this vessel and traveling to the lesser curvature of the stomach, where it will anastomose with the left gastric artery. As it travels superiorly, the proper hepatic artery divides into right and left hepatic arteries, which travel into the liver. Before entering the liver, the right hepatic artery most typically gives off the cystic artery to the gallbladder. The other branch of the common hepatic artery is the gastroduodenal artery. The small supraduodenal artery, which travels to the superior duodenal flexure, most frequently branches from the gastroduodenal artery. This vessel gives off the posterior superior pancreaticoduodenal artery, anterior superior pancreaticoduodenal artery, and, finally, right gastroomental (gastroepiploic) artery, which travels along the right side of the greater curvature of the stomach.
The splenic artery, the celiac trunk’s third branch, is a large, coiled artery that travels to the left of the abdomen superior to, or within, the pancreas. It generally gives off a large dorsal pancreatic artery to supply the head and body of the pancreas, along with the greater pancreatic artery a bit further down its length. The artery to the tail of the pancreas can be seen as a small branch of the distal splenic artery connecting with the greater and dorsal pancreatic arteries by means of the inferior pancreatic artery within the pancreas. Near its terminus, the splenic artery gives off several branches that pierce the hilus of the spleen to supply the organ. As this is happening, the short gastric arteries leave the superiormost aspect of the splenic artery to supply the fundus of the stomach. Inferiorly, the left gastroomental (gastroepiploic) artery leaves the splenic artery to supply the left side of the stomach’s greater curvature and anastomose with the right gastroomental artery.
The blood supply of the stomach and abdominal esophagus is accomplished by six primary and five secondary arteries. The primary arteries are the (1) right gastric and (2) left gastric, coursing along the lesser curvature; (3) right gastroomental and (4) left gastroomental, coursing along the greater curvature (each of these four vessels giving off branches to the anterior and posterior surfaces of the stomach, where they anastomose); (5) splenic, which gives off in its distal third a variable number (2 to 10) of short gastric branches, and from its superior or inferior terminal division the left gastroomental; and (6) gastroduodenal, by direct small branches (1 to 3) and, frequently, by a large pyloric branch.
The secondary arteries are the (7) anterior superior pancreaticoduodenal (end branch of the gastroduodenal) by short twigs and, frequently, by a large pyloric branch; (8) supraduodenal artery of varied origin (gastroduodenal, posterior superior pancreaticoduodenal, hepatic, right gastric) which, in addition to supplying the first inch of the duodenum, often sends one or more branches to the pylorus; (9) posterior superior pancreaticoduodenal, predominantly the first collateral of the gastroduodenal, which, in its tortuous descent along the left side of the common bile duct to reach the back of the pancreas and duodenum, frequently gives off one or more pyloric branches, the latter, in some instances, uniting with the supraduodenal and right gastric; (10) dorsal pancreatic artery of varied origin (splenic, hepatic, celiac, superior mesenteric), the right branch of which anastomoses with the superior pancreaticoduodenal, gastroduodenal, and right gastroomental and, in so doing, sends small branches to the pylorus; (11) left inferior phrenic, which, after passing inferior to the esophagus in its course to the diaphragm, in most instances gives off a large recurrent branch to the cardioesophageal end of the stomach posteriorly, where its terminals anastomose with other cardioesophageal branches derived from the left gastric, splenic terminals, aberrant left hepatic from the left gastric, and descending thoracic esophageal branches.
This conventional form of the celiac with its three branches occurs in only 55% of the population, for the celiac often lacks one or more of its typical branches. Whether in a complete or incomplete form, the celiac trunk forms a hepatosplenogastric trunk in about 90% of the population. The celiac may omit the left gastric, so that a hepatosplenic trunk is present (3.5%); omit one or more of the hepatic arteries, so that a splenogastric trunk is present (5.5%); or omit the splenic, so that a hepatogastric trunk is present (1.5%). Additional branches may originate from the celiac trunk: the dorsal pancreatic (22%), inferior phrenic (74%), and, occasionally, even the middle colic or an accessory middle colic artery. In many instances the common hepatic artery is absent, being replaced from the superior mesenteric, aorta, or left gastric.
|ARTERIES OF LIVER, PANCREAS, DUODENUM, AND SPLEEN|
Typically, the left gastric artery arises from the celiac (90%), most commonly as its first branch. In remaining cases it arises from the aorta, the splenic or hepatic artery, or a replaced hepatic trunk. Varying in width from 2 to 8 mm it is considerably larger than the right gastric, with which it anastomoses along the lesser curvature. Before its division into anterior and posterior gastric branches, the left gastric supplies the cardioesophageal end of the stomach, either by a single ramus that subdivides or by two to four rami given off in seriation by the main trunk. Accessory left gastric arteries occur frequently. They are (1) a large left gastric from the left hepatic; (2) a large ascending posterior gastroesophageal ramus from the splenic trunk or from the superior splenic polar; or (3) a slender, thread-like cardioesophageal branch from the celiac artery, aorta, first part of the splenic artery, or inferior phrenic artery.
The terminal branches of the left gastric anastomose with (1) branches of the right gastric; (2) short gastric arteries from the splenic terminals or splenic superior polar or left gastroomental; (3) cardioesophageal branches from the left inferior phrenic (via its recurrent branch), an aberrant left hepatic artery from the left gastric (A), or an accessory left gastric from the left hepatic (B) and from descending rami of thoracic esophageal branches. The degree of anastomosis about the cardioesophageal end of the stomach is variable; it may be very extensive or very sparse.
In about one fourth of the population, the left gastric artery gives off a large left hepatic artery (2 to 5 mm wide, 5 cm long) to the left lobe of the liver. Such a left hepatic may be either replaced or accessory. In the replaced type (12%), no celiac left hepatic is present, the entire blood supply to the lateral segment of the left lobe being derived from the left gastric artery. The accessory left hepatic is an additive vessel that supplies a region of the left lobe of the liver (either the superior or inferior area of the lateral segment) not supplied by the incomplete celiac left hepatic. From the functional point of view, none of the hepatic arteries is ever “accessory” because every hepatic artery supplies a definite region of the liver. In view of prevalent anatomic variations, every gastric resection should be preceded by an exploratory examination to determine what type of left gastric artery is present, for severance of a left hepatic derived from the left gastric results in ischemia and fatal necrosis (7th to 16th day) of the left lobe of the liver, as repeatedly evidenced in postmortem examinations. Quite frequently, the left gastric gives off an accessory left inferior phrenic and, in some instances, the left inferior phrenic itself.
The celiac trunk may be incomplete when the right or left hepatic arteries arise from some other source. The common hepatic artery may arise in its entirety from the superior mesenteric artery (C); the superior mesenteric artery may provide the right hepatic artery in its entirety, also supplying blood to the gallbladder (D); and the superior mesenteric artery may supply an accessory right hepatic artery, which may or may not supply the gallbladder (E). The common hepatic artery may also branch very proximally, giving off an early right and left hepatic arteries while the right hepatic and gastroduodenal arteries branch from each other further to the right (F). The left lobe of the liver may also receive an accessory left hepatic artery from the right hepatic artery (G), or the right hepatic artery may cross anterior to the hepatic duct before entering the substance of the liver (H).
|ARTERIES OF STOMACH, DUODENUM, PANCREAS, AND SPLEEN|
Invariably, the right gastric artery is much smaller (2 mm) than the left gastric (4 to 5 mm), with which it anastomoses. On occasion (8%) it gives off the supraduodenal or a spray of twigs to the first part of the duodenum. Predominantly, the gastroduodenal artery arises from the common hepatic (75%), but, in some instances, especially with a split celiac trunk, it may arise from the left hepatic (10%), right hepatic (7%), replaced hepatic trunk from the superior mesenteric or aorta (3.5%), or even directly from the celiac or superior mesenteric artery (2.5%). These atypical origins are correlated with the mode of branching of the celiac artery, for the common hepatic may divide only into the gastroduodenal and right hepatic (leaving the left hepatic to be replaced from the left gastric) or into the gastroduodenal and left hepatic with replacement of the right hepatic from the superior mesenteric. Typical branches of the gastroduodenal are (1) the posterior superior pancreaticoduodenal (90%); (2) the anterior superior pancreaticoduodenal; and (3) the right gastroomental. Inconstant branches are (1) the right gastric (8%); (2) the supraduodenal (25%); (3) the transverse pancreatic (10%); (4) a cystic artery, either the superficial branch or the entire cystic (3%); (5) an accessory right hepatic; and (6) the middle colic or an accessory middle colic (rarely).
The relatively large posterior superior pancreaticoduodenal artery (1 to 3 mm in width) forms an arcade on the back of the head of the pancreas, with branches to the duodenum. In many instances (10%), the artery arises from a source other than the gastroduodenal and, when it arises from the latter, it does so as its uppermost collateral branch and not as an end branch. The right gastroomental artery is considerably larger than the left gastroomental and, in its course, extends far beyond the midline of the greater curvature of the stomach, where it anastomoses with the left gastroomental artery. Of great surgical import is the fact that, in many instances (10%), this anastomosis is not grossly visible, it being absent or reduced to small arterial twigs that dwindle to nothing before the two meet. The infragastric omental arc, formed by the right and left gastroomental arteries, gives off a large pyloric branch and then a variable number of ascending gastric and descending omental or anterior omental branches. The omental branches descend between the two anterior layers of the great omentum. The short ones anastomose with neighboring vessels, and the long ones proceed to the distal free edge of the great omentum, where they turn upward to become the posterior omental arteries. Many of these join the large omental arc situated in the posterior layer of the great omentum below the transverse colon. The arc is usually formed by the right omental (first branch of the right gastroomental) and left omental, a branch of the left gastroomental. Slender arteries ascend from the arc and anastomose with similar branches (posterior omentals) given off from the middle colic or left colic and from the transverse pancreatic coursing along the inferior surface of the pancreas. The ultimate and penultimate branches of the posterior omental arteries anastomose with the vasa recta of the middle colic but, apparently, are not of sufficient caliber to take over the blood supply if the middle colic has been rendered functionless. Aberra- tions of the right gastroomental are (1) an origin from the superior mesenteric (1.5%) or with the middle colic and superior pancreaticoduodenal (1%); (2) anastomoses with the middle colic, via a large vessel (1%); and (3) an origin from a gastroduodenal derived from the superior mesenteric.
Usually, the left gastroomental arises from the distal end of the splenic artery (75%) or from one of its splenic branches (25%) near its terminus. It may be replaced by two to three vessels, the main artery coming from the splenic trunk and the others from an inferior splenic polar artery. Branches of the left gastroomental are (1) short fundic branches (two to four); (2) a variable number of ascending short gastric arteries; (3) several short and long descending omental branches, some of which communicate with similar branches from the right gastroomental artery; (4) pancreatic rami to the tail of the pancreas, one of which, when large, is termed the artery to the tail of the pancreas; (5) an inferior splenic polar artery; and (6) the left omental artery, which descends in the great omentum to form the left limb of the omental arc, the right limb being formed by the right omental artery from the right gastroomental or transverse pancreatic artery.
|ARTERIES OF DUODENUM AND HEAD OF PANCREAS|
The blood supply of the duodenum and head of the pancreas is one of the most variant in the body and, surgically considered, one of the most difficult to manipulate. The first inch of the duodenum is a critical transition zone. Paucity or insufficiency of its blood supply has repeatedly been correlated causatively with the tendency of ulcers to perforate the superior part of the duodenum just beyond the pylorus. Typically, the superior, anterior, and posterior surfaces of the first inch of the duodenum are supplied by the supraduodenal artery, which may be derived from either of two nearby arteries, the posterior superior pancreaticoduodenal artery or gastroduodenal and, in the remaining cases, from the right gastric, hepatic, or right hepatic. The supraduodenal artery frequently communicates with branches of the right gastric, gastroduodenal, and anterior and posterior superior pancreaticoduodenal arteries. The remaining portions of the duodenum are supplied by branches from two pancreaticoduodenal arcades, one anterior and the other posterior to the head of the pancreas. It is by virtue of these two arcades that the duodenum is the only section of the gut that has a double blood supply, one to its anterior surface and one to its posterior surface.
The anterior pancreaticoduodenal arcade is formed by the anterior superior pancreaticoduodenal artery, the smaller of the two end branches of the gastroduodenal artery. After making a loop of a half circle or less on the anterior surface of the pancreas, medial to the groove between the pancreas and duodenum, it sinks into the pancreas, turns to the left, and ascends, and upon reaching the posterior surface of the head of the pancreas, joins the anterior inferior pancreaticoduodenal artery, a branch from the superior mesenteric artery. The arcade gives off 8 to 10 relatively large branches to the anterior surface of all three portions of the duodenum and, in many instances, 1 to 3 branches to the first part of the jejunum; they reach the jejunum by passing deep to the superior mesenteric artery. The arc also supplies numerous pancreatic branches, some of which are arranged in arcade fashion and anastomose with branches given off by the dorsal pancreatic artery, derived from the first part of the splenic or hepatic artery.
The posterior pancreaticoduodenal arcade is made by the posterior superior pancreaticoduodenal artery, which is the first branch of the gastroduodenal given off by the latter above the duodenum above the upper border of the head of the pancreas, where it may be hidden by connective tissue. In about 10% of cases, it has a decidedly different origin, being derived from the hepatic (4%), right hepatic (2%), aberrant right hepatic from the superior mesenteric (3%), or dorsal pancreatic (1%). After its typical origin from the gastroduodenal, the artery (1 to 3 mm in width) descends for 1 cm or more on the left side of the common bile duct and then, after crossing the latter anteriorly, descends for several centimeters along its right side before swinging to the left and downward to form the posterior arcade. The major portion of the U- or V-shaped posterior arcade lies posterior to the head of the pancreas, at a level superior to that of the anterior arcade. It comes into full view when the duodenum is mobilized and turned forward to expose its posterior surface. It is covered by a fold of connective tissue sufficiently thin that its branches can be seen. It is accompanied by a venous arcade that lies superficial to the arterial arcade and that empties directly into the portal vein. The arcade crosses the intrapancreatic part of the common bile duct (to which it supplies blood) posteriorly. Ultimately, the posterior superior pancreaticoduodenal artery unites with the inferior pancreaticoduodenal artery derived from the superior mesenteric at a higher level than that of the anterior arcade (40%), or it anastomoses with a posterior branch of a common inferior pancreaticoduodenal, the latter receiving both the anterior and posterior arcades (60%). The main branches, arising from the posterior pancreaticoduodenal arcade, are (1) several descending branches (two to three) to the first part of the duodenum, one of which may be the supra- duodenal; (2) duodenal branches to the posterior surfaces of the descending, transverse, and ascending duodenum; (3) small pancreatic branches that are far less numerous and are shorter than those of the anterior arcade; (4) ascending branches (one or more) to the supraduodenal portion of the common bile duct; and (5) a cystic artery (entire or its superficial branch), which, in about 4% of cases, stems from the first part of the posterior superior pancreaticoduodenal or at its site of origin from the gastroduodenal. In the majority of instances, the anterior and posterior pancreaticoduodenal arcades have a variant anatomic structure, in the sense that the arcades may be double, triple, or even quadruple. When multiple arcades are present, it is the outer arcade near the duodenum that usually supplies the latter with its branches, whereas the inner arcades supply only pancreatic branches and ultimately become united with other branches of the celiac trunk.
|HEPATIC ARTERY VARIATIONS|
With every duodenal resection, three important vascular arrangements must be borne in mind:
1. The entire blood supply of the duodenum and head of the pancreas may be completely dissociated from the superior mesenteric. This occurs when an aberrant right hepatic from the superior mesenteric, coursing behind the head of the pancreas, gives off one or two inferior pancreaticoduodenal arteries to receive the anterior or posterior pancreaticoduodenal arcade (or both).
2. The anterior or posterior pancreaticoduodenal arcade (or both) often ends via one or more inferior pancreaticoduodenal arteries derived from the left side of the superior mesenteric or from its first, second, or third jejunal branch, a fact to be explored in every gastrojejunostomy, lest the blood supply of the duodenum be impaired and rendered insufficient for viability of that section of the gut.
3. In resections of the duodenum, extreme care should be taken to maintain an adequate blood supply to the anterior and posterior surfaces of the stumps. The duodenal branches from the pancreaticoduodenal arcades are end arteries, and if these are ligated, the suture lines pass through ischemic parts that may become necrotic and break. This can result in “blowout” of the duodenal stump; such an event has repeatedly been fatal, excessive devascularization of the stump being the direct cause of the fatal issue.