Abdominal Vasculature PDF

Abdominal Vasculature Abdominal Vascular Structures Function of the circulatory system Transport gases, nutrient materials, and other essential substances to the tissues Transport waste products from the cells to the appropriate sites for excretion Arteries Hollow elastic tube...

Abdominal Vasculature Abdominal Vascular Structures Function of the circulatory system Transport gases, nutrient materials, and other essential substances to the tissues Transport waste products from the cells to the appropriate sites for excretion Arteries Hollow elastic tubes that carry blood away from the heart Enclosed within a sheath that includes a vein and nerve Smaller arteries contain less elastic tissue and more smooth muscles than the larger arteries. Elasticity of the larger arteries is important for maintaining steady blood flow. The pulsatile abdominal aorta will not change in diameter with changes in respiration. Veins Hollow collapsible tubes with diminished tunica media that carry blood toward the heart Appear collapsed (little elastic tissue or muscle within their walls) Have a larger total diameter than the arteries Move blood more slowly Contain special valves that prevent backflow and permit blood to flow only in one direction—toward the heart IVC should dilate slightly with suspended respiration. Vascular Structure Physiology Arteries divide into progressively smaller branches Arterioles Arterioles lead into the Capillaries Capillaries are minute vessels that form a network in which materials are exchanged between blood and tissue fluid. Blood is then collected in the small veins or venules. Venules unite to form larger vessels that eventually return the blood to the heart Anatomy of Vascular Structures Arteries and veins have three layers: 1.Tunica intima (inner layer), which itself has three layers A layer of endothelial cells lining the arterial passage (lumen) A layer of delicate connective tissue An elastic layer made up of a network of elastic fibers 2.Tunica media (middle layer) Smooth muscle fibers with elastic and collagenous tissue 3.Tunica adventitia (external layer) Loose connective tissue with bundles of smooth muscle fibers and elastic tissue The vasa vasorum makes up the tiny arteries and veins that supply the walls of blood vessels. Anatomy of Vascular Structures Abdominal Arteries Aorta Largest artery in the body Divided into five sections: Root of the aorta Ascending aorta and arch Descending aorta Abdominal aorta and branches Bifurcation into iliac arteries Sonography of the Aorta Sonography of the Aorta Sonography of the Aorta Clinical reasons for sonographic evaluation: Pulsatile abdominal mass Abdominal pain radiating to the back Abdominal bruit Hemodynamic compromise in the lower legs Arterial system may be affected by calcification, aneurysm, infection, rupture or thrombosis Size of Abdominal Aorta and Iliac Branches MEN WOMEN Diameter +/-SD (cm) Diameter +/-SD (cm) AORTA 2.0 +/-2.5 1.7 +/-1.5 CIA 1.3 +/-2.0 1.2 +/-1.3 Pathology of the Aorta Abdominal Aortic Aneurysm (AAA) Ectasia Pseudoaneurysm Rupture Dissection Atherosclerosis Abdominal Aortic Aneurysm Risk factors: Tobacco Hypertension Vascular disease Chronic obstructive pulmonary disease (COPD) Family history for abdominal aortic aneurysm Genetic disorder (Marfan's, EDS) Abdominal Aortic Aneurysm Symptoms: Palpable abdominal mass Back pain Drop in hematocrit (rupture) May be asymptomatic “Pseudo-Pulsatile” Abdominal Masses Other masses that can simulate a pulsatile abdominal mass Retroperitoneal tumor Huge fibroid uterus Paraaortic nodes Because the mass is adjacent to the aorta, pulsations are transmitted from the aorta to the mass. Abdominal Aortic Aneurysm >3cm and involves all three vessel layers bulbous, saccular, and fusiform Important to note aneurysm location in relation to the renal arteries Supra renal At the level of the renal arteries Infrarenal Ninety-five percent (95%) Mural, atherosclerosis Mycotic aneurysm = infection Abdominal Aortic Aneurysm Fusiform Saccular Bulbous Pseudo Abdominal Aortic Aneurysm Abdominal Aortic Aneurysm Abdominal Aortic Aneurysm Size and treatment options: 5 to 6 cm Surgical intervention >6 to 7 cm Might be too risky for surgery Treatment of Abdominal Aortic Aneurysms Surgical intervention Stent (Cath lab) vs Graft (surgery) Endovascular graft suggested with renal and iliac involvement Endovascular stent grafts are a less invasive True vs Pseudoaneurysm A= true B= pseudoaneurysm Pseudoaneurysm A pulsatile hematoma that results from the leakage of blood into the soft tissue abutting the punctured artery Blood escapes through a hole in the intima of the vessel wall but is contained by the deeper layers of the aorta or by the adjacent tissue. Doppler the “neck” and within the aneurysm Thrombin injection guided with ultrasound Pseudoaneurysm Rupture of Aortic Aneurysm 50% mortality rate Aneurysms >5 cm have a 25% cumulative incidence of rupture over 8 years. Symptoms of a rupture Excruciating abdominal pain Shock Expanding abdominal mass Rupture of Aortic Aneurysm Aortic Dissection The separation between two layers of the vessel wall “Intimal flap” on ultrasound Abdominal Aortic Branches Abdominal Aortic Branches (main visceral) Celiac Axis/Trunk (CA/CT) Superior Mesenteric (SMA) Renal Arteries Main and middle superrenal Gonadal Arteries Inferior Mesenteric (IMA) Abdominal Aortic Branches (parietal visceral) Inferior Phrenic Artery Lumbar Arteries Median Sacral Artery Gastrodoudenal Artery (GDA) Common Hepatic Artery Splenic Artery Abdominal Aortic Branches: Celiac Axis Abdominal Aortic Branches: Celiac Axis First major branch of the abdominal aorta Arises anteriorly Branches into Splenic Artery Left Gastric Artery Common Hepatic Artery Low resistance (continuous forward flow in diastole) Abdominal Aortic Branches: Celiac Axis Normal abdominal protocol. Longitudinal images. SMA, superior mesenteric artery; CT, celiac trunk; Ao, aorta. Celiac Axis Splenic Artery Abdominal Aortic Branches: Common Hepatic Artery Abdominal Aortic Branches: Superior Mesenteric Gives rise to: Second main branch of the Inferior pancreatic artery, Duodenal artery, Colic artery, Ileocolic artery, Intestinal artery abdominal aorta Arises on the anterior surface of the aorta, inferior to the CT Runs parallel to the aorta Different wave patterns pre and post prandial SMA Abdominal Aortic Branches: Renal Arteries Aries from the posterior and lateral aspects of the aorta, inferior to SMA Course posterior to the renal veins Right renal artery courses posterior to the IVC* Low resistance wave pattern 10-20% of the population will have duplicates Renal Arteries Doppler Flow Patterns in Renal Disease Abdominal Aortic Branches: Inferior Mesenteric A. Last major branch Three main branches Left colic Sigmoid Superior rectal arteries Distribution is to the left transverse colon, descending colon, sigmoid colon, and rectum. Low resistance flow Abdominal Veins Inferior Vena Cava  Formed by the union of the common iliac veins at the level of the fifth lumbar vertebra.  Ascends vertically through the retroperitoneal space on the right side of the aorta, posterior to the liver and piercing the central tendon of the diaphragm at the level of the eighth thoracic vertebra to enter the right atrium of the heart. Its entrance into the lesser sac separates it from the portal vein. Caudal to the renal vein entrance, the inferior vena cava (IVC) shows posterior “hammocking” through the bare area of the liver. Inferior Vena Cava Inferior Vena Cava Longitudinal images. A, the hepatic vein (HV) drains into the IVC at the diaphragm. B, The IVC is the posterior border of the portal vein. Inferior Vena Cava Tributaries of the IVC Three anterior hepatic veins Three lateral tributaries Right suprarenal vein (the left suprarenal vein drains into the left renal vein) Renal veins Right testicular or ovarian vein Five lateral abdominal wall tributaries: the inferior phrenic vein and the four lumbar veins Three veins of origin: the two common iliac veins, and the median sacral vein Anterior Tributaries to the Inferior Vena Cava Anterior Tributaries to IVC The hepatic veins (HV) are the largest visceral tributaries of the inferior vena cava. They originate between the segments of the liver and drain posteriorly into the inferior vena cava at the level of the diaphragm. The hepatic veins return deoxygenated blood from the liver. The veins collect blood from the three minor tributaries within the liver: the right hepatic vein drains the right lobe of the liver, the middle hepatic vein drains the caudate lobe, and the left hepatic vein drains the left lobe of the liver The middle and left hepatic veins may fuse before emptying into the inferior vena cava. Anterior Tributaries to the Inferior Vena Cava Abnormalities of the Inferior Vena Cava Congenital abnormalities: Double IVC Infrahepatic interruption of the IVC Azygous continuation IVC dilation IVC tumor IVC thrombosis Inferior Vena Cava Tumors and Thrombus Inferior Vena Cava Filters: Thrombosis Most common origin of pulmonary emboli is venous thrombosis from the lower extremities. Surgical and angiographic placement of transvenous filters into the IVC have been used to prevent recurrent embolization in patients who cannot tolerate anticoagulants. Renal Veins Right Renal Vein: Left Renal Vein: Flows directly from the hilum of the right Arises medially to exit from the hilus of the kidney into the posterolateral aspect of the kidney inferior vena cava Flows from the left kidney posterior to the It seldom accepts tributaries; the right superior mesenteric artery and anterior to adrenal and right gonadal veins enter the the aorta to enter the lateral wall of the inferior vena cava directly. inferior vena cava Renal Veins Left Renal Vein Portal Venous System Portal Vein Forms posterior to the pancreas by the union of the superior mesenteric vein and splenic veins Trunk is 5 to 7 cm in length. Carries blood from the intestinal tract to the liver by means of its two main branches: the right and left portal veins Doppler Flow Patterns in the Abdominal Veins Normal Portal Vein Hepatopetal (towards the liver) flow Continuous flow pattern; varies slightly with respirations Abnormal chronic portal vein obstruction* Prehepatic, post hepatic and intrahepatic extrahepatic portal vein is not visualized. Echogenic area is present in the porta hepatis. Periportal collaterals are present. Doppler Flow Patterns in the Abdominal Veins Abnormal Portal Venous Hypertension Hepatofugal flow (away from the liver) Low velocity in portal vein Patent umbilical vein Loss of respiratory variation Caused by liver cirrhosis, obstruction of the portal vein, hepatic vein, IVC, or prolonged congestive heart failure. Sonographic Findings Dilated portal, splenic, superior mesenteric vein Patent paraumbilical vein Varices Splenomegaly with dilated splenic radicles Diminished response to respiration in portal system Dilated hepatic and splenic arteries Ascites Small liver with irregular surface or large liver with abnormal texture Portal Venous System Portal Venous System Portal Triad Contains a branch of the portal vein, hepatic artery, and bile duct within a connective tissue sheath This gives the portal vein an echogenic wall. Portal Venous System Splenic Vein A tributary of the portal circulation Begins at the hilum of the spleen, where it is formed by the union of several veins Joined by the short gastric and left gastroepiploic veins Runs along the posteromedial border of the pancreas Portal Venous System Superior Mesenteric Vein Runs posterior to the neck of the pancreas where it joins the splenic vein to form the main portal vein  Inferior Mesenteric Vein Drains the left third of colon and upper colon and ascends retroperitoneally along the left psoas muscle Begins midway down the anal canal as the superior rectal vein Receives many tributaries along its way, including the left colic vein Drains several tributaries: the left colic vein (descending colon), sigmoid vein (sigmoid colon), and superior rectal vein (upper rectum)