Interstitial pneumonia is a type of pneumonia mainly characterized by inflammation of the pulmonary interstitium，mostly in infants and young children, and is often secondary to acute infectious diseases such as measles, pertussis, and influenza.
Clinical presentation and pathology
Pathologically, there is mainly inflammatory infiltration in the wall of bronchioles and pulmonary interstitium. Inflammation can spread along lymphatic vessels to cause lymphangitis and lymphadenitis. Bronchioles are often partially or completely obstructed due to inflammation, congestion, and edema. Clinical manifestations include fever, cough, tachypnea, and cyanosis.
Imaging manifestations
X-ray
The middle and lower fields of both lungs are predilection sites. The manifestations are increased and hazy lung markings and reticular or small patchy opacities. Diffuse emphysema may be present. Increased hilar density and unclear structure are often caused by inflammatory infiltration in the perihilar interstitium.
CT
CT is often used for diagnosis and differential diagnosis in early or mild patients. The main manifestations are thickening of the bilateral bronchovascular bundles and reticular or small patchy opacities. Enlargement of hilar and mediastinal lymph nodes may be present, and occasionally little pleural effusion can be seen.
Diagnosis and differential diagnosis
Interstitial pneumonia needs to be distinguished from bronchopneumonia. The latter is mainly characterized by small, scattered, patchy opacities in the middle and lower lung fields of both lungs.