It is the area that is in the central portion of each lung.
Located in the medial (middle) aspect of the lung. The hilum is where the bronchi, arteries, veins and nerves enter and leave the lungs.
Each lung (right and left) can be divided into four main sections: the apex, the base, the root and the hilum, or pulmonary hilum.
The pulmonary roots are relatively complicated structures that consist mainly of the main bronchi and the pulmonary arteries and veins. The pulmonary hilum is located on the medial aspect of each lung, and is the only site of entry or exit of structures associated with the lungs.
That is, both lungs have a region called hilum, which serves as the junction between the root of the lung and the lung.
Structurally, the hilum is a large depressed triangular area in the lung that is just above the center of the mediastinum surface and behind the cardiac impression of each lung, and is closer to the posterior border than to the front.
The rib cage is separated from the lung by a two-layer membranous coating called the pleura. The hilum is where the connection between the parietal pleura (covering the rib cage) and the visceral pleura (covering the lung), which denotes the point of encounter between the mediastinum and the pleural cavities.
Anatomy of the Hilio Pulmonar
Both the right and left lungs have a hilum that is approximately in the middle of the lungs, and slightly toward the back (closer to the vertebrae than the front of the chest).
Each lung can be visualized with an apex (the top) a base (the bottom) a root and a hilus.
The main bronchi, the pulmonary arteries, the pulmonary veins and the nerves are the structures that enter and leave the lungs in this region.
The lymph nodes, called hilar lymph nodes, are also present in this region. Both hilus are similar in size, the left hilum is usually slightly higher in the chest than the right hilum.
On a chest radiograph, the hilar region will reveal a shadow consisting of the combination of lymph nodes, pulmonary arteries and pulmonary veins.
Due to the overlap of these structures, it can sometimes be difficult to detect the enlargement of these lymph nodes or the presence of a mass in this region. This is one of the reasons why common chest x-rays can overlook lung cancer.
Imaging tests such as CT scans (especially with contrast) can lead to a better visualization of these structures.
Occasionally, more tests may be needed, such as PET, bronchoscopy with endobronchial ultrasound, or mediastinoscopy to better visualize the region or to obtain a biopsy sample.
Abnormalities and Diseases of the Hilio Pulmonar
This hilar region of the lung can be affected by tumors in the region (including metastatic tumors), enlargement of the hilar lymph nodes, as well as abnormalities of the pulmonary arteries or veins.
The main reasons why the hilus of one or both lungs may appear enlarged on an x-ray.
Tumors and lymphadenopathy: cancers such as lung cancer and lymphomas, as well as cancer that has spread to this region from other parts of the body (metastatic cancer) can cause masses in this region, as well as enlarged lymph nodes to metastasis.
Pulmonary venous hypertension (elevated pressure in the pulmonary veins):Pulmonary venous hypertension can occur due to medical conditions such as heart failure and heart valve problems, such as mitral stenosis and mitral regurgitation.
Pulmonary arterial hypertension (PAH – elevated pressure in the pulmonary arteries): PAH can occur as a primary disease (not secondary to another problem) or as a secondary problem that in turn is caused by chronic obstructive pulmonary disease (COPD).
Increased pulmonary blood flow: conditions such as congenital cyanotic heart disease (heart defects present at birth that cause a blue tint in the skin due to a reduced oxygen content) can cause an increase in pulmonary blood flow.
Hilar lymphadenopathy (enlarged hilar lymph nodes): Enlarged lymph nodes in the hilum can appear in either the right or left hilum (bilateral lymphadenopathy) or on one side (asymmetric lymphadenopathy). Causes can include:
Lung cancer : Lung cancer is the most common cause of unequal hilar regions in adults, both due to the presence of a tumor and the presence of affected lymph nodes.
Other cancers: metastatic breast cancer can cause hilar lymphadenopathy due to the spread of cancer to this region and affected lymph nodes. Lymphoma and other mediastinal tumors can also cause enlargement of the hilar lymph nodes.
Tuberculosis: worldwide, tuberculosis is the most common cause of hilar adenopathy in children.
Inflammation: conditions such as sarcoidosis, amyloidosis and silicosis can cause hilar lymphadenopathy. Sarcoidosis is the most common cause of bilateral enlargement of the hilar lymph node.
Other infections such as mycobacteria, viral infections such as infectious mononucleosis, berylliosis, tularemia, histoplasmosis and coccidiomycosis, can cause the lymph nodes to increase in this region.