A 70-year-old man is brought to the emergency department because of sudden-onset severe abdominal and back pain that began 1 hour ago. He has hypertension, hyperlipidemia, and a 50-pack-year smoking history. Temperature is 36.9°C (98.4°F), blood pressure is 82/50 mm Hg, pulse is 128/min, and respirations are 24/min. Physical examination shows a tender pulsatile abdominal mass. CT angiography shows a ruptured infrarenal abdominal aortic aneurysm. An axial contrast-enhanced CT slide of the upper abdomen is shown (see image below).
Which of the following best describes the normal position of the abdominal aorta at this level?
The correct answer is:
A) Anterior to the vertebral body and left of the inferior vena cava
The abdominal aorta is a retroperitoneal midline vascular structure that descends anterior to the vertebral bodies and slightly to the patient’s left. The inferior vena cava lies to the patient’s right of the abdominal aorta. On axial CT images, the patient’s right side appears on the viewer’s left. In this image, the axial contrast-enhanced CT is at the level of the renal arteries, and the arrow is pointing to the abdominal aorta. The patient’s ruptured aneurysm is below this level.
Answer choice B: Anterior to the vertebral body and right of the inferior vena cava, is incorrect. This reverses the normal relationship between the abdominal aorta and inferior vena cava. The inferior vena cava lies to the patient’s right of the aorta, while the aorta lies to the patient’s left of the inferior vena cava.
Answer choice C: Posterior to the left kidney and lateral to the spleen, is incorrect. The abdominal aorta lies medial to the kidneys and anterior to the vertebral column, not posterior to the left kidney. The spleen is an intraperitoneal left upper quadrant organ and is not a landmark for the normal position of the infrarenal aorta.
Answer choice D: Posterior to the pancreas and anterior to the stomach, is incorrect. At upper abdominal levels, the aorta can lie posterior to the pancreas, but it is not normally anterior to the stomach. The stomach is an intraperitoneal organ positioned anterior to the pancreas and aorta.
Answer choice E: Within the hepatoduodenal ligament and medial to the common bile duct, is incorrect. The hepatoduodenal ligament contains the portal triad: portal vein, proper hepatic artery, and common bile duct. The abdominal aorta is retroperitoneal and does not travel within the hepatoduodenal ligament.
Key Learning Point
On axial abdominal imaging, the abdominal aorta lies anterior to the vertebral bodies and to the patient’s left of the inferior vena cava.
