Superior mesenteric artery

The superior mesenteric artery (SMA) is one of the three non-paired major visceral arteries in the abdominal cavity arising from the abdominal aorta and supplying the midgut.

Gross anatomy

Origin

Single vessel arising anteriorly from the abdominal aorta at the level of L1, usually just below the celiac trunk.

Course

Courses anteroinferiorly, behind the neck of the pancreas and splenic vein, crossing anterior to the left renal vein. It emerges anterior to the uncinate process of the pancreas and crosses anterior to the third part of the duodenum. It then enters the upper portion of the small bowel mesentery and runs along the root of the mesentery downwards to the right. Branches to the jejunum and ileum are given off to the left, and branches to the proximal and mid colon are given off to the right.

The SMA terminates at the ileum where it anastomoses with the ileal branch of the ileocolic artery. Some anatomists believe the ileocolic artery is the terminal portion of the SMA and that what many consider the terminal SMA is the last of the ileal branches.

Branches

• inferior pancreaticoduodenal artery

Left-sided

• jejunal branches
• ileal branches

Right-sided

• ileocolic artery
• right colic artery
• middle colic artery

Marginal artery of Drummond

The terminal branches of SMA (ileocolic, right colic, middle colic) and inferior mesenteric artery (left colic, sigmoid) which supply the colon are linked together by a continuous arterial circle or arcade along the mesenteric border, known as the marginal artery of Drummond. This arcade is considered a normal structure, although may be absent in some people. It may supply collateral flow between SMA and IMA circulations ³. From this marginal artery, straight vessels (also known as vasa recta) pass to the colon.

Relations

The superior mesenteric vein (SMV) should be positioned to the right of the SMA, especially within the 3 cm from origin. Reversal of SMA/SMV relationship is classically associated with intestinal malrotation, although distally (>6 cm from origin) this may be a normal finding ⁶. 

Supply

The SMA is the artery to the midgut. It supplies the gut from the ampulla of Vater of the 2^nd part of the duodenum to the distal third of the transverse colon, and includes structures in between such as ⁵: 

• jejunum
• ileum
• appendix
• cecum
• ascending colon
• hepatic flexure
• proximal 2/3rd of the transverse colon 

The inferior pancreaticoduodenal artery also supplies the head of the pancreas.

Variant anatomy

• replaced right hepatic artery (10-17%) ⁴
• replaced left hepatic artery (2-4%) ⁴
• replaced common hepatic artery (1-3%) ⁴
• accessory right hepatic artery
• celiacomesenteric trunk (uncommon) ⁴
• replaced splenic artery
• replaced left gastric artery
• replaced dorsal pancreatic artery
• arc of Buhler
• arc of Riolan

Related pathology

• superior mesenteric artery syndrome
• SMA stenosis
• mesenteric ischemia from SMA occlusion
• SMA thrombosis
• lower GI bleeding
• nutcracker syndrome