Blood Supply of Small Intestine
For the typical pattern of arterial branching of the small intestines, please refer to Plates 1-1 and 1-2. In this section, we will describe the variations concerning the origin, course, anastomoses, and distribution of the vessels supplying the small intestine. These variations are so frequent that conventional textbook descriptions are inadequate for anyone attempting procedures in the area. Typically, the superior mesenteric artery supplies almost all of the small intestine aside from the proximal duodenum, which receives blood from the supraduodenal and superior pancreaticoduodenal arteries. These arteries are branches of the gastroduodenal artery, a branch of the common hepatic artery, which is itself a branch of the celiac trunk.
The
distance between the celiac trunk and the superior mesenteric artery varies
from 1 to 23 mm but is typically between 1 and 6 mm. These major vessels branch
from the abdominal aorta; in rare cases, the vessels form a single massive
vessel, a celiacomesenteric trunk, that gives off the common hepatic,
splenic, left gastric, and superior mesenteric arteries. However, in some cases
of celiacomesenteric trunk the left gastric artery is a small separate branch arising
directly from the abdominal aorta (A). A far more frequently encountered
variation (0.4% to 6% of the population, Kahraman and associates 2002) of these
vessels is a hepatomesenteric trunk. This occurs when the superior
mesenteric trunk fuses with the common hepatic, right hepatic, or left hepatic
artery (B, C, D, and E). If the hepatomesenteric trunk includes the common
hepatic artery, there will also be a gastrosplenic trunk giving rise to
the splenic and left gastric arteries (B). If the hepatomesenteric trunk gives
rise to a right hepatic artery (C) or an
accessory right hepatic artery (D and E), there will be either an incomplete
celiac trunk or a complete celiac trunk contributing the remaining hepatic
vessels (C and D). The cystic artery may arise from either the right hepatic
artery or accessory right hepatic artery (C, D, and E).
Variations
that are even less frequent have been described. A splenomesenteric trunk develops
when the superior mesenteric and splenic arteries arise from a common trunk
(F). In such cases, there will be a separate hepatogastric trunk branching
into common hepatic and left gastric arteries. If the superior mesenteric,
splenic, and common hepatic arteries come from a common trunk of the abdominal
aorta (G), the result is a hepatosplenomesenteric trunk, with a separate
left gastric artery arising from the aorta or from the left inferior phrenic
artery, creating a gastrophrenic trunk. Occasion- ally, the right gastroomental
artery may branch from the superior mesenteric artery (H) instead of taking
its normal departure from the gastroduodenal artery.
The first jejunal branch of superior mesenteric origin may be very large (6 mm in diameter), but in many instances, it is very small (1 to 2 mm) and forms anastomoses with the inferior pancreaticoduodenal artery or has a common origin with it. The distribution, as well as the caliber, of all the following intestinal branches of the superior mesenteric artery varies considerably, and smaller branches may alternate without any general rule or order. An odd situation may be faced during gastric resection, when the right gastroomental artery and the first jejunal branch arise from a common pancreaticoduodenal trunk coming from the superior mesenteric artery. Closer to the small intestine itself, small (4- to 6-cm) segments may be vascularized by straight arteries derived from a separate anterior and posterior arcade, each serving the anterior and posterior surface of the same region of the gut. Though numerous other examples of variations concerning the origin and communication of the first jejunal branches could be enumerated, those cited seem sufficient to justify the requirement of a careful inspection of these vessels while operating in this region.
