Sectional Anatomy Abdomen/Pelvis Vasculature

Objectives List vessels found in the abdominal region List vessels found in the pelvic region Identify the locations of and relationships between abdominal and pelvic vasculature After completing this topic, you should be able to: List vessels found in the abdominal region List vessels found in the pelvic region Identify the locations of and the relationships between abdominal and pelvic vasculature

Abdomen/Pelvis Imaging The abdomen and pelvis are commonly scanned for generalized pain or following traumatic injury. Sectional anatomy images of these body regions can reveal numerous pathologies that are enhanced by the injection of intravenous iodinated contrast media. Similar to the chest, the vessels opacified with contrast will be determined by the rate and phase of the injection. Identifying vessels and understanding their relationships is essential for the radiologic technologist to recognize dissections, organs lacerations, and aneurysms that can be visualized on abdomen/pelvis exams.

Abdomen/Pelvis Imaging The abdomen and pelvis are frequently imaged together in CT. This is especially true following traumatic injury when free air and fluid may be evident. When the doctor orders a CT Abdomen, the scan begins at the base of the lungs and extends through midsacrum. If a pelvis is imaged alone, such as when a hip fracture is evaluated, the scan begins above the iliac crest through all bony pelvic anatomy and finishing at some level in the femurs. When the abdomen and pelvis is ordered together, the scan begins at the base of the lungs and extends through the entire pelvis to the top of the femurs. Of course, protocols may vary according to radiologist preferences and the patient’s area of injury. This image pictured here demonstrates the scan lines on a scout image for an abdomen and pelvis exam.

Celiac Trunk & Branches There are five main branches that arise from the abdominal aorta. These vessels include the celiac truck or axis, superior mesenteric artery, right and left renal arteries, and the inferior mesenteric artery. The first branch off of the abdominal aorta is the celiac trunk. The celiac trunk has 3 branches that originate from it. These vessels include the common hepatic artery, the splenic artery, and the left gastric artery. Typically, the common hepatic and splenic artery branches are easily demonstrated on a axial CT image. The celiac trunk looks like a stalk coming directly from the abdominal aorta. The common hepatic and splenic arteries curve to the right and left towards their respective organs. The celiac trunk with its branches forms an “M” like the golden arches from McDonald’s.

Celiac Trunk & Branches Depending upon the selected protocol and slice thicknesses, branches from the celiac trunk may not be perfectly visualized simultaneously as they were in the previous image. This image demonstrates the celiac trunk with the blue arrow and the common hepatic artery is identified with the red arrow. The green arrow displays the abdominal aorta. Other anatomy demonstrated in this axial CT image include the liver with the gall bladder seen on the right side of the image. The spleen is visualized on the left of the image with the upper pole of the left kidney beginning to come into view. The pancreas is seen in the midline of the image with the pancreatic tail pointing towards the spleen.

Celiac Trunk & Branches This image provides a good illustration of the celiac trunk and its tributaries. Additionally, this image combines other vessels included within the abdominal region. As you can see, the vessels are often placed close together making it difficult to distinguish between them. Understanding their spatial relationships helps to identify each vessel and determine when pathology is present.

Splenic Artery & Vein The splenic artery is a branch originating from the celiac trunk. It is marked by the red arrow in this image. The splenic vein is also visible on this image and is indicated by the blue arrow. Keep in mind, arteries get smaller as they move away from the heart and veins become larger as they return back to the heart. For this reason, the splenic vein is larger than the splenic artery. Also demonstrated on this image are the liver, which is the large organ located on the right side of the image. The spleen is located on the bottom left of the image with the left kidney coming into view. The contrast filled stomach is also visualized on this image. The abdominal aorta is bright white from the injection of intravenous contrast media.

Portal Vein The portal vein is a major vessel demonstrated when imaging the abdominal region. The portal vein is formed when the splenic vein and the superior mesenteric vein merge together. In this image, the portal vein is identified with the red arrow. Other important vessels also visualized on this image are the inferior vena cava demonstrated with the green arrow and the abdominal aorta shown with the blue arrow. A large portion of the liver is displayed on the right side of the image. On the left side of the image, the spleen is primarily seen with a portion of the stomach and colon highlighted white through the administration of oral contrast media.

Portal & Splenic Veins The portal vein is formed when the splenic and superior mesenteric veins merge together. This image illustrates both the portal vein and the splenic vein highlighted with contrast. Also seen on this image are both the right and left kidneys coming into view. Additionally, a calcified abdominal aorta is identified at the midline of the image.

Superior Mesenteric Artery This image demonstrates the second major branch arising from the abdominal aorta. The superior mesenteric artery appears as a stalk extending from the abdominal aorta on an axial slice. The superior mesenteric artery provides oxygenated blood to the small intestines, pancreas, and the right half of the colon. Other anatomy identified in this image are the kidneys placed in the retroperitoneum, and a portion of the liver along with the gallbladder on the right side of the image. A small piece of the spleen still remains on the left side of the image. Bowel is also seen in this picture. However, it is not as easily distinguished because oral contrast media has not been administered.

Renal Arteries & Veins The renal arteries are the third and fourth major branches arising from the abdominal aorta. Remember, arteries branch into arteries, and veins empty into veins. This is an important tip when trying to distinguish between the renal arteries and veins. First, let’s identify the renal artery. In this image, the red arrow is pointing to the left renal artery that is well demonstrated with intravenous contrast media. The left renal artery is connected to the abdominal aorta displayed with the green arrow. The renal arteries provide oxygenated blood to the kidneys. Next, we will locate the left renal vein pointed out with the blue arrow. The left renal vein is emptying into the inferior vena cava which is evident with the purple arrow. The inferior vena cava accepts venous drainage from the lower extremities and trunk of the body and empties into the right atrium of the heart. The small round circle, highlighted bright white, and sitting above the left renal vein, is the superior mesenteric artery that branches from the abdominal aorta.

Renal Veins This image provides an excellent view of the renal veins bilaterally. The right and left renal veins, demonstrated with the blue arrows, are emptying into the inferior vena cava labeled with a green arrow. Also seen on this image are the abdominal aorta sitting above the vertebral body and the superior mesenteric artery sitting above the left renal vein. The abdominal aorta and superior mesenteric artery are identified with the red arrows on this image.

Renal Arteries The renal arteries are the third and fourth major branches arising from the abdominal aorta. The renal arteries are demonstrated with the red arrows in this image. The green arrow identifies the abdominal aorta.

Common Iliac Arteries At approximately the region of L4, the abdominal aorta will bifurcate into the right and left common iliac arteries. In some patients, this bifurcation will be seen at the same level or around the level of the iliac crest. In this image, the right and left common iliac arteries are represented with red arrows. The blue arrow shows the expanding inferior vena cava which will branch shortly into the right and left common iliac veins. Also seen within this image are the psoas muscles displayed adjacent to the lumbar vertebra. Additionally, the oral contrast filled colon is visualized. On the right side of the image the cecum is demonstrated.

This image demonstrates many vasculature structures This image demonstrates many vasculature structures. Focusing upon the major vessels, we can identify the right and left common iliac arteries which are branches from the abdominal aorta. Similar to the previous image the inferior vena cava is seen adjacent to the right common iliac artery. The superior aspect of the right iliac crest is also coming into view.

In previous images, the right and left common iliac arteries were demonstrated as they branched off of the abdominal aorta. Here, we can identify the internal and external iliac arteries which are branches arising from the common iliac arteries. The internal iliac arteries provide oxygenated blood to the pelvis and reproductive organs. The external iliac arteries provide arterial circulation to the lower extremities. Also seen on this image are the external and internal iliac veins. So where do these vessels come from? When the inferior vena cava branches, it creates the right and left common iliac veins. Similar to the arteries, the common iliac veins bifurcate into the internal and external veins.