Which major vascular structure is NOT evaluated during an abdominal ultrasound?

The pulmonary artery is not evaluated during an abdominal ultrasound because this imaging modality primarily focuses on the abdominal organs and structures, rather than thoracic vascular components. The abdominal ultrasound assesses the major vascular structures located within the abdominal cavity, such as the abdominal aorta, which supplies blood to the lower body; the celiac trunk, which branches off the aorta to supply blood to the stomach, spleen, and liver; and the inferior vena cava, which is responsible for draining deoxygenated blood from the lower body back to the heart. The pulmonary artery, on the other hand, is part of the cardiovascular system located in the thoracic cavity and is not relevant to abdominal imaging, making it the correct answer to the question.