How to tell if there is a lung problem on chest X-ray

When lung disease occurs, a chest X-ray, also known as a chest x-ray, is often needed. A chest X-ray can reveal some lung problems. Generally, chest radiographs are used for lung infection and screening. Chest X-rays are also often used for diagnosis and examination of pneumothorax, hydropneumothorax or fractures. In addition, there may be foreign objects in the chest, or some other lung diseases. These are better diagnostic methods.

How to determine whether lung texture is normal?

We know that one side of the lung field is divided into three equal parts from the hilum to the periphery of the lung, which are called the inner, middle and outer zones of the lung. Under normal circumstances, the inner and middle zones of the lung have lung texture, while the outer zone does not. If lung texture appears in the outer zone, it means that the lung texture has increased. Conversely, if the transparency of the inner and middle zones increases, the lung texture has decreased.

The distinction between the inner, middle and outer zones of the lungs also has another significance, which is the judgment of lung compression during pneumothorax. Generally speaking, the inner, middle and outer zones of the lungs account for 60%, 30% and 10% of the lung volume respectively. I remember an article saying that when the edge of lung compression is located in the outer zone of the lung field (1/3 of the chest cavity/outer lung field), lung compression is about 50%, and when it reaches the middle zone it is about 75%. This is easy to understand because the volume is largest around the outside of the chest cavity and gradually decreases inward.

Mediastinum: Located behind the sternum, in front of the thoracic vertebrae, and between the two lungs, with the thoracic entrance above and the diaphragm below. It is mainly composed of the heart, large blood vessels, trachea, large bronchi, esophagus, thymus, etc. The chest X-ray can only show the outline of the trachea, main bronchi and mediastinum adjacent to the lungs. In the picture below, you can see that the white area between the two lung fields is the mediastinum.

Diaphragm: It is located between the thoracic and abdominal cavities and is dome-shaped. The top of the right diaphragm is generally at the level of the 5th to 6th anterior intercostal space. Usually, the right diaphragm is slightly higher than the left diaphragm. The diaphragm, chest wall and heart form the costophrenic angle and cardiophrenic angle respectively. The diaphragm shadow is also well shown in the above figure.

Lobes and segments

In terms of anatomical structure, the lung lobes are naturally separated by the interlobar fissures of the pleura. The left lung is divided into upper and lower lobes by the oblique fissure, and the right lung is divided into upper, middle and lower lobes by the horizontal fissure (transverse fissure) and the oblique fissure. In chest X-ray films, the interlobar fissure pleura can be visualized as a thin line when it is parallel to the X-ray direction. Among them, the horizontal fissure of the right lung can often be seen in the frontal chest X-ray (as shown in the figure).

Horizontal fissure of right lung. A thin linear horizontal fissure of the right lung can often be seen in the frontal chest X-ray. It is located in the middle of the right lung field and runs horizontally from the edge of the lung field to the right hilum. Above the horizontal fissure is the right upper lobe, and below it are the right middle and lower lobes.

The triangular arrows indicate the oblique fissures of the two lungs, which are in the shape of thin lines. The oblique fissure of the right lung starts from the fourth thoracic vertebra, runs obliquely forward and downward to the front of the diaphragm, about 2 to 3 cm away from the anterior costophrenic angle. The starting point of the oblique fissure of the left lung is slightly higher than that of the right lung, and the oblique fissures of the two lungs roughly overlap on the lateral chest X-ray. The white arrow marks the horizontal fissure, which starts near the midpoint of the oblique fissure and extends horizontally or slightly downward to the anterior chest wall.

Indications for chest X-ray:

1. Infection or screening: One of the main tasks of emergency chest X-rays is to diagnose lung infections and find out the causes of cough, chest pain, dyspnea, hemoptysis, etc. The role of chest X-ray is to confirm the diagnosis, assess the prognosis, and detect hidden lesions.

2. Fracture: Rib fractures are common in chest trauma, usually multiple rib fractures. Fractures of ribs 1-4 often indicate greater violence and severe injuries. The axillary and dorsal segments of ribs 3-7 are prone to fractures. The front ends of ribs 8-10 are connected to the costal arch, and the front ends of ribs 11-12 are free and elastic, making them less likely to fracture. If a fracture occurs due to greater external force, the diaphragm and subdiaphragm may be involved, causing damage to intra-abdominal solid organs.

3. Pneumothorax and hydropneumothorax: They are more common in spontaneous pneumothorax or pneumothorax and hydropneumothorax caused by trauma penetrating the pleura.

4. Foreign body in the chest: Firearm wounds, stab wounds, or foreign bodies in the trachea are often retained in the chest. The anterior-posterior and lateral views of the chest can determine the presence and approximate location of the metal foreign body.