transient tachypnoea of the newborn (TTN)

Transient tachypnea of the newborn, also known as retained fetal fluid or wet lung disease, presents in the neonate as tachypnea for the first few hours of life, lasting up to one day. The tachypnea usually resolves within 48 hours.

Epidemiology

Transient tachypnea is one of the commonest causes of neonatal respiratory distress, particularly in term or near term newborns. It is estimated to affect 1-2% of all neonates with an equal gender predilection.

Clinical presentation

Infants present in respiratory distress, classically with grunting and nasal flaring, within the first six hours of life. There can be mild cyanosis.

Pathology

Amniotic fluid is normally expressed from the lungs during vaginal delivery and then absorbed after birth. Also, prostaglandins dilate pulmonary lymphatics to absorb excess fluid. In transient tachypnea of the newborn there is build-up of fluid in the lungs thought due to the reduced mechanical squeeze and reduced capillary and lymphatic removal of amniotic fluid. This reduced clearance of fluid from the lungs is why some have proposed that it is more commonly seen in Cesarean section deliveries since the thoracic compression that would occur in a normal vaginal delivery does not take place.This prostaglandin imbalance is also worsened in other situations like maternal diabetes or asthma, and in male newborns.

Radiographic features

Plain radiograph

• interstitial edema - predominantly perihilar
  • often seen as perihilar streakiness
• pleural effusions that are usually small
• mild to moderate cardiomegaly has been described rarely
• severe cases may have perihilar alveolar opacities
• normal chest radiograph by 48-72 hours postpartum

Ultrasound

• the double lung point sign has a reported specificity of 94.8% in severe cases
• can rule out in the presence of consolidated lung with air bronchograms

Differential diagnoses

• congenital heart disease
  • heart size is usually normal in transient tachypnea of the newborn and there is rapid spontaneous resolution
• neonatal pneumonia
• aspiration 
  • meconium aspiration
• persistent fetal circulation
• respiratory distress syndrome: lung volumes are slightly decreased in RDS but are normal to slightly hyperinflated in transient tachypnea of the newborn

See also

• neonatal respiratory distress (causes)

Siehe auch:

• Herzfehler
• Mekoniumaspiration
• retained fetal lung fluid

und weiter:

• fetal conditions associated with maternal diabetes
• neonatal chest radiograph in the exam setting
• Acute Respiratory Distress Syndrome neonatal