Abdominal vasculature
dilatation of the aorta equal to or exceeding 3 cm in diameter; also known as AAA.
a localized widening or dilatation of a blood vessel.
an abnormal connection between an artery and vein; also known as arteriovenous shunting.
small saccular aneurysms primarily affecting the cerebral arteries.
a result of a tear in the intimal lining of the artery, creating a false lumen within the media. This false lumen allows blood to dissect the media and adventitia layers.
dilatation of an artery when compared with a more proximal segment. In the abdominal aorta, the ectatic dilatation does not exceed 3.0 cm.
characterized by a uniform dilatation of the arterial walls; most common type of abdominal aortic aneurysm.
a saccular dilatation of a blood vessel caused by a bacterial infection.
dilatation of an artery as a result of damage to one or more layers of the arterial wall caused by trauma or aneurysm rupture; also known as pulsatile hematoma.
dilatation of an artery characterized by a focal outpouching of one arterial wall; most often caused by trauma or infection.
Physiology and anatomy
Functions of the vascular system
• Arteries and arterioles carry oxygenated blood away from the heart.
• Veins and venules carry blood toward the heart.
• Capillaries connect the arterial and venous systems.
• Extremity veins contain valves.
• Valves extend inward toward the intima.
Arterial anatomy (fig. 13-1)
Abdominal aorta
• Originates at the diaphragm and courses inferiorly until it bifurcates into the right and left common iliac arteries.
• Tapers in size as it courses anterior and inferior in the abdomen.
• Common iliac arteries are the terminal branches of the abdominal aorta.
• Common iliac artery bifurcates into the external and internal (hypogastric) iliac arteries.
• External iliac artery becomes the common femoral artery after passing beneath the inguinal ligament.
• Internal iliac artery bifurcates into anterior and posterior divisions.
Main visceral branches of the abdominal aorta
Celiac axis (CA)
• First major branch of the abdominal aorta.
• Arises from the anterior aspect of the aorta.
• Branches into the splenic, left gastric, and common hepatic arteries.
• Low-resistance blood flow, with continuous forward flow in diastole.
Superior mesenteric artery (SMA)
• Second major branch of the abdominal aorta.
• Arises from the anterior surface of the aorta, inferior to the celiac axis.
• Courses inferiorly and parallel to the aorta.
• Branches supply the jejunum, ileum, cecum, ascending colon, portions of the transverse colon, and the head of the pancreas.
• High-resistance multiphasic blood flow when fasting.
• Low-resistance elevated systolic and diastolic velocities, with continuous forward flow in diastole following a meal.
• Distance from the anterior wall of the aorta to the posterior wall of the SMA should not exceed 11 mm.
Main renal arteries
• Right renal artery arises from the anterior lateral aspect of the abdominal aorta.
• Left renal artery arises from the posterior lateral aspect of the abdominal aorta.
• Located 1.0 to 1.5 cm inferior to the superior mesenteric artery.
• Course posterior to the renal veins.
• Right side arises superior to the left and courses posterior to the inferior vena cava.
• Renal artery bifurcates into segmental arteries at the renal hilum.
• Renal artery gives rise to the inferior suprarenal artery.
• Low-resistance blood flow, with continuous forward flow in diastole.
Inferior mesenteric artery
• Last major branch of the abdominal aorta superior to the aortic bifurcation.
• Arises from the anterior aorta.
• Courses inferior and to the left of midline.
• Supplies the left transverse colon, descending colon, upper rectum, and sigmoid.
• Source of collateral flow to the lower extremities.
• Visualized on ultrasound in an oblique plane, slightly to the left of midline and approximately 1 cm superior to the aortic bifurcation.
• Low-resistance blood flow, with continuous flow through diastole.
Main parietal branches of the abdominal aorta
Inferior phrenic artery
• Arises from the anterior aspect of the abdominal aorta branching into the right and left inferior phrenic arteries just below the diaphragm near the level of the 12th thoracic vertebrae.
• Supplies the inferior portion of the diaphragm.
Additional abdominal arteries
Gastroduodenal artery (GDA)
• Branch of the common hepatic artery.
• Lies between the superior portion of the duodenum and the anterior surface of the pancreatic head.
Hepatic artery
• Common hepatic artery is a branch of the celiac axis.
• Gives rise to the gastroduodenal artery and is now termed the proper hepatic artery.
• Proper hepatic artery gives rise to the right gastric artery.
• Courses adjacent to the portal vein.
• The proper hepatic artery bifurcates into the right and left hepatic arteries at the hepatic hilum.
• The right hepatic artery gives rise to the cystic artery to supply the gallbladder.
• Low-resistance blood flow, with continuous flow through diastole.
• Increased flow velocity is associated with jaundice, cirrhosis, lymphoma, and metastases.
Venous anatomy (fig. 13-2)
Inferior vena cava (IVC)
• Formed at the junction of the right and left common iliac veins.
• Carries oxygen-depleted blood from the body superiorly to the right atrium of the heart.
• Major abdominal branches include lumbar veins, right gonadal vein, renal veins, right suprarenal vein, inferior phrenic vein, and hepatic veins.
Main venous tributaries
Common iliac veins
• Drain blood from the lower extremities and pelvis.
• Formed by the junction of the external and internal iliac veins.
Renal veins
• Course anterior to the renal arteries.
• Left renal vein courses posterior to the superior mesenteric artery and anterior to the abdominal aorta.
• Left renal vein receives the left suprarenal and gonadal veins.
• Left renal vein may appear dilated because of compression from the mesentery.
• Right renal vein has a short course to drain into the lateral aspect of the IVC.
Hepatic veins
• Lie at the boundaries of the hepatic segments (intersegmental) and course toward the IVC.
• Three major branches: left, middle, and right hepatic veins.
• Right hepatic vein courses coronally between the anterior and posterior segments of the right hepatic lobe.
• Middle hepatic vein follows an oblique course between the left and right hepatic lobes.
• Left hepatic vein courses posterior between the medial and lateral segments of the left hepatic lobe.
• Doppler demonstrates spontaneous, multiphasic, and pulsatile blood flow toward the IVC (hepatofugal).
• Increase in blood flow with inspiration and diminished flow with Valsalva maneuver.
Additional abdominal veins
Main portal vein
• Drains the gastrointestinal tract, pancreas, spleen, and gallbladder.
• Provides approximately 70% of the liver’s blood supply.
• Formed by the junction of the splenic and superior mesenteric veins.
• Bifurcates into the right and left portal veins just beyond the porta hepatis.
• 1.3 cm in diameter in adults greater than 20 years of age.
• 1.0 cm in diameter between 10 and 20 years of age.
• Demonstrates phasic low-flow velocities toward the liver (hepatopetal).
• Blood flow will decrease with inspiration and increase with expiration.
• Diameter will increase after a meal.
• Additional tributaries include:
Splenic vein
• Joins the superior mesenteric vein to form the main portal vein.
• Courses posterior to the pancreas and crosses anterior to the superior mesenteric artery.
• Demonstrates spontaneous phasic flow away from the spleen and toward the liver.
• Normal adult diameter is 10 mm or less.
• Increase in caliber with inspiration.
• Drains the spleen, pancreas, and a portion of the stomach.
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