The pulmonary hilum is located in the depression behind and above the cardiac impression on the pulmonary mediastinal plane.Equivalent to between the 2nd and 4th front ribsa bronchial tubeEntrance and exit of blood vessels, nerves and lymphatic vessels.At the pulmonary hilum, the pulmonary vein is located in the front, the bronchus is in the rear, and the pulmonary artery is in the middle.There are several lymph nodes in the hilum of lung.There is an esophageal impression behind the right pulmonary hilum and an azygos vein groove above.There are aortic arch and thoracic aorta impression above and behind the left pulmonary hilum.In addition, clinically, the entrances and exits of various structures of the lung root are also called the first pulmonary hilum.The place where the lobar bronchus and its accompanying lobar arteries, veins and lymphatic vessels enter and exit the lung lobe is called the second pulmonary hilum.The third bronchus (that is, segmental bronchus) and its accompanying blood vessels, nerves and other entrances and exits are called the third hilar lung.
The major branches of pulmonary artery and pulmonary vein are the main components, especially pulmonary artery.On the AP radiograph, the hilum of lung is located in the inner zone of the middle field of both lungs, and the left hilum is usually 1~2cm higher than the right.The left and right hilum of lung can be divided into upper and lower parts.The upper part of the right pulmonary hilum is composed of the superior pulmonary vein trunk, the superior pulmonary artery and the retrogressive branch of the inferior pulmonary artery trunk, and its outer edge is formed by the inferior posterior vein trunk of the superior pulmonary vein;The lower part is composed of the right lower pulmonary artery trunk, which has a clear contour because of the background of the air containing middle bronchus on its inner side. The width of the right lower pulmonary artery trunk in normal adults is not more than 15mm.The blunt angle formed by the intersection of the upper and lower parts is called the right hilar angle.The left pulmonary hilum is mainly composed of branches of the left pulmonary artery and the upper pulmonary vein, and the upper part is formed by the left pulmonary artery arch, presenting a semicircular shadow with smooth edges, which is easy to be mistaken for a mass.The lower part is composed of left lower pulmonary artery and its branches, most of which are covered by cardiac shadow.In the lateral position, most of the pulmonary hili on both sides overlap, and the right pulmonary hilum is slightly forward, like a trailing comma. The front edge is the upper pulmonary vein trunk, and the rear upper edge is the left pulmonary artery arch. The trailing tail is composed of two lower pulmonary artery trunks.Local Anatomy explains that the hilum of lung is a depression in the middle of the mediastinum of the two lungs, also known as the first hilum of lung, with access to the main bronchi, pulmonary arteries, bronchial vessels, lymphatic vessels and pulmonary plexus.The branch and branch of lobar bronchi and pulmonary blood vessels of each lung lobe enter and exit the lung lobe, which is called the second lung hilum.
Indicators of lung root shadow
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(1) Bilateral pulmonary arteries and left and right main bronchi are the main components of the lung root shadow in the anteroposterior and lateral chest radiographs.
(2) The projection of pulmonary artery on each side is the center of pulmonary root shadow on each side.The central point of lateral chest radiograph is the sectional projection of the left main bronchus, and the projection of bilateral pulmonary arteries is around this small transparent circle.
(3) In adults, the left lung root shadow is always higher than the right lung root shadow.But not in children.The shadow of lung root grows gradually from newborn to old age;The right lung root shadow is larger than the left, which is completely consistent with anatomy;The value of lung root shadow is smaller in women than in men.
(4) The highest density area of the lung root shadow in the chest radiograph is the projection of the left pulmonary artery at the upper part of the left lung root. Since its direction is consistent with the X-ray, it forms a dense round shadow.According to the same principle, the projection of the right pulmonary artery on the lateral chest radiograph is also the highest density area of the lateral pulmonary root shadow.
(5) As CT and MRI have entered the field of modern radiology, they will make more detailed and high-resolution analysis and identification of lung root shadow in different sections and directions, which will dwarf the discussion of lung root shadow in plain film.
