respiratory distress syndrome

Respiratory distress syndrome (RDS) is a relatively common condition resulting from insufficient production of surfactant that occurs in preterm neonates.

On imaging, the condition generally presents as bilateral and relatively symmetric diffuse ground glass lungs with low volumes and a bell-shaped thorax.


RDS is also known as hyaline membrane disease (not favored as reflects non-specific histological findings), neonatal respiratory distress syndrome, lung disease of prematurity (both non-specific terms), or as some authors prefer surfactant-deficiency disorder .


The incidence is estimated at 6 per 1000 births .  Uncommon after 36 weeks' gestation due to development of pneumocyte surfactant production around 35 weeks .

Clinical presentation

Respiratory distress presents in the first few hours of life in a premature baby. Signs include tachypnea, expiratory grunting, and nasal flaring. The infant may or may not be cyanosed. Substernal and intercostal retractions may be evident.

Risk factors include maternal diabetes, greater prematurity, perinatal asphyxia and multiple gestations.

Associated abnormalities are those that can occur in prematurity: germinal matrix hemorrhage, necrotizing enterocolitis, patent ductus arteriosus, delayed developmental milestones, hypothermia and hypoglycemia.


Immature type II pneumocytes cannot produce surfactant. The lack of surfactant increases the surface tension in alveoli causing collapse. Patients have a decreased lecithin to sphingomyelin ratio. Damaged cells, necrotic cells, and mucus line the alveoli.

Although most cases are related to prematurity alone, rarely patients may have genetic disorders of surfactant production and can present in a similar clinical and radiological manner .

As the alveoli are collapsed (microscopically), the lungs are collapsed macroscopically as well. It is a diffuse type of adhesive atelectasis.

Radiographic features

Plain radiograph
  • low lung volumes are mandatory (atelectasis - lung collapse).
  • diffuse granular opacities (ground glass), bilateral and symmetrical - "white lungs".
  • air bronchograms may be evident.
  • bell-shaped thorax.
  • hyperinflation (in a non-ventilated patient) excludes the diagnosis; if the patient is intubated there might be hyperinflation.

RDS can be safely excluded if the neonate has a normal chest radiograph at six hours after birth.

If treated with surfactant therapy, there may be an asymmetric improvement.

On transabdominal ultrasound, retrodiaphragmatic hyperechogenicity can be seen. If this hyperechogenicity does not resolve by day 9-18 on follow up ultrasound, it helps in the prediction of risk of development of bronchopulmonary dysplasia .

Treatment and prognosis

Exogenous surfactant administration. Supportive oxygen therapy.


Differential diagnosis


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