48: Vessels of the Retroperitoneum


Abdominal Aorta

The abdominal aorta is the principal artery of the abdomen, pelvis and lower limb.


The abdominal aorta is the continuation of the descending thoracic aorta. It begins at the level of T12, slightly to the left of midline, posterior to the diaphragm and anterior to the T12 vertebral body. It passes inferiorly, remaining anterior to the lumbar vertebrae, before dividing into the paired common iliac arteries.


The relations of the abdominal aorta are:

  • Left, with the left kidney
  • Right, with the azygos vein (superiorly), inferior vena cava and right coeliac plexus
  • Posteriorly, with the vertebral bodies of T12 to L4.
  • Anteriorly, with the right lobe of the liver, stomach, pancreas and small bowel. The left renal vein passes anterior to the aorta.


The principal branches of the abdominal aorta are:

  • The coeliac trunk or axis, a short vessel that contributes to supply of the liver, stomach, pancreas and spleen
  • The superior mesenteric artery which supplies the small bowel, proximal large bowel, and the proximal pancreas
  • The paired renal arteries which supply the kidneys. The right renal artery passes posterior to the inferior vena cava
  • The paired gonadal arteries, the course of which varies between men and women.
  • The inferior mesenteric artery which supplies the descending and sigmoid colon, and the rectum.
  • Smaller branches include lumbar arteries which supply the vertebrae and spinal canal, and inferior phrenic branches which supply the diaphragm.

Coeliac Axis / Trunk

The coeliac axis is a 2 cm stub that arises from the anterior aspect of the abdominal aorta, at about T12. It rapidly divides into numerous branches.

Common Hepatic Artery and Branches

The common hepatic artery is the larger branch of the coeliac axis, and passes laterally to the porta hepatis within the lesser omentum. It gives off the gastroduodenal artery as it passes superior to the pylorus, followed by the right gastric artery which passes back along the lesser omentum to supply the lesser curvature of the stomach. It continues as the hepatic artery into the porta hepatis, giving off the cystic artery before dividing into right and left hepatic arteries.

Splenic Artery and Branches

The splenic artery passes to the left in the retroperitoneum. It gives off numerous branches to the pancreas, which lies inferiorly. It also gives off the left gastroepiploic artery and short gastric arteries to the lateral greater curvature of the stomach.

Left Gastric Artery

The smallest branch of the coeliac axis, the left gastric passes to the gastro-oesophageal junction, where it gives of an oesophageal branch. It then passes along the lesser curvature of the stomach to anastamose with the right gastric.

Superior Mesenteric Artery

The superior mesenteric is the second anterior artery to arise from the abdominal aorta, about 1 cm below the coeliac axis and posterior to the pancreas. It passes inferiorly, laterally and slightly anteriorly, in front of the uncinate process of the pancreas. The left renal vein passes between this artery and the aorta, as does the third part of the duodenum. The superior mesenteric gives off numerous branches to the small bowel and proximal large bowel.

Inferior pancreaticoduodenal artery

This small vessel curves superiorly to anastamose with branches of the gastroduodenal artery of the coeliac axis, behind the pyloris.

Small intestinal branches

Ilial and jejunal branchs pass into the mesentery of the small bowel, supplying the small intestine.

Middle and Right Colic Arteries

The middle colic passes to the right, away from the artery, to supply the transverse colon. The right colic branch supplies the distal ascending colon and the splenic flexure.

Iliocolic trunk

The iliocolic trunk passes inferiorly to the right of the superior mesenteric. It supplies the caecum, proximal ascending colon, appendix and the terminal ilium.

Inferior Mesenteric Artery

The smallest of the anterior arteries, the inferior mesenteric arises at the level of L3. It passes inferiorly, over the origin of the left common iliac artery, and enters the mesentery of the sigmoid colon, becoming the superior rectal artery. This artery descends in the mesorectum to supply most of the rectum.

Left Colic Artery

The left colic arises soon after the inferior mesenteric begins its descent, passing laterally over the left kidney to the descending colon. It contributes some supply to the transverse colon.

Sigmoid branches

As it passes through the root of the sigmoid mesocolon, the inferior mesenteric gives off several branches to the sigmoid colon.

Renal Arteries

The paired renal arteries supply the kidney. They arise just below the origin of the superior mesenteric. Both arteries are posterior to the pancreas; the right renal artery passes behind the inferior vena cava and right renal vein.

Gonadal Arteries

Testicular Arteries

The testicular arteries are long and thin, arising just beneath the renal arteries. They pass just beneath the peritoneum, resting on psoas major, in an anterior and inferior curve, reaching the internal inguinal ring and entering the spermatic cord.

Ovarian Arteries

The ovarian arteries follow a similar course to the testicular intially, but on reaching the mesovarium enter its substance to supply the ovary. A branch enters the broad ligament to supply the uterine tube.

Median Sacral Artery

The median sacral artery is a single branch which arises from the bifurcation of the aorta. It passes inferiorly and posteriorly, in front of the sacrum, terminating in the coccyx.


Inferior Vena Cava

The inferior vena cava is the major vessel for the return of blood to the heart from the abdomen and pelvis. Many abdominal viscera drain via the portal system to the liver; but hepatic veins still empty into the inferior vena cava just prior to its entry into the right atrium. The IVC is typically considered in four parts:

  • The long abdominal section which runs from L5 to L1
  • The intrahepatic part that lies within the substance of the liver
  • The short suprahepatic segment between the liver and the diaphragm
  • The short thoracic part that empties into the right atrium

The relations of the inferior vena cava are:

  • Anteriorly (from inferior to superior), the right common iliac artery, the peritoneal cavity (including small intestine, large intestine), the third part of the duodenum, the head of the pancreas, the first part of the duodenum, the peritoneal cavity again, and then the liver.
  • Posteriorly, with the lumbar vertebrae and twelfth thoracic vertebra. The right renal artery crosses posteriorly at the level of L2, and the right suprarenal artery crosses posteriorly just above this.
  • Right lateral, with the right ureter, right kidney, the second part of the duodenum and the right lobe of the liver.
  • Left lateral, with the aorta and left ureter.

Tributaries are numerous:

  • The IVC is formed by the union of the two common iliac veins at the level of L5.
  • Numerous lumbar veins enter its posterolateral aspect
  • The right gonadal vein typically drains into the IVC directly
  • The paired renal veins enter at about L1; the left is significantly longer and passes anterior to the abdominal aorta to reach the left kidney. The left gonadal vein typically empties into the left renal vein, as does the left suprarenal vein.
  • The right suprarenal vein usually empties directly into the IVC
  • The large left, middle and right hepatic veins empty into the IVC during its intrahepatic course, just prior to its passage through the caval foramen in the diaphragm.

The thoracic course of the IVC is very short.

Portal Vein

The portal venous system drains blood from the spleen, pancreas and gastrointestinal tract to the liver, separate to the systemic venous return. It is not covered in this section.