Transient tachypnea of the newborn appears soon after birth and has been identified as occurring with cesarean birth and infant sedation. [1, 2, 3, 4, 5] It may be accompanied by chest retractions, expiratory grunting, or cyanosis, which can be relieved with minimal oxygen. Recovery is usually complete within 3 days. [6, 7]
Radiologically, this syndrome frequently is termed wet lung disease. In the medical literature, discussions concerning transient tachypnea of the newborn can also be found under the following names: retained fetal lung liquid, retention of fetal lung fluid, respiratory distress syndrome type II, transient respiratory distress of the newborn, and neonatal retained fluid syndrome.
The lungs usually are affected diffusely and symmetrically, and the condition is commonly accompanied by a small pleural effusion. [8, 9] The clinical course of transient tachypnea is relatively benign when compared with the severity suggested by chest films. Radiographic resolution by the second or third day characterizes this entity and differentiates it from other possible disorders; if radiographic resolution is not complete by the third day or if respiratory symptoms persist longer than 5 days, an alternative diagnosis should be sought.
See the images below.
Standard chest radiography is the preferred radiologic examination. Initially, it may be difficult to distinguish transient tachypnea from other causes of respiratory distress of the newborn.
The differential diagnosis includes Hyaline Membrane Disease, Meconium Aspiration, and neonatal pneumonia. Other conditions to be considered include respiratory distress syndrome, congenital lymphangiectasia, congenital heart disease, polycythemia, cerebral hyperventilation, and anemia/hypovolemia.
Differentiation from other causes of neonatal respiratory distress may take time. Initial evaluation, monitoring, and basic supportive care must cover all diagnostic contingencies.
Findings of transient tachypnea of the newborn (TTN) on chest radiographs may include mild, symmetrical lung overaeration; prominent perihilar interstitial markings; and small pleural effusions (see the first image below). [7, 8, 9, 10, 11] Occasionally, the right side may appear more opacified than the left.
The radiographic appearance at times can mimic the diffuse, granular appearance of hyaline membrane disease but without pulmonary underaeration. Neonates with transient tachypnea are usually at term. Radiographic lung changes also may resemble the coarse, interstitial pattern of other causes of pulmonary edema or the irregular pattern of lung opacification seen in meconium aspiration syndrome.
The degree of confidence is rather low. Clinicoradiologic correlation helps confirm the diagnosis. Timing also is a key diagnostic factor.
A persistent radiographic finding of cardiomegaly should raise suspicions of congenital heart disease. Evaluation by a pediatric cardiologist and echocardiographic imaging should follow.  Ultrasound also permits relatively easy differentiation between hyaline membrane disease, transient tachypnea of the newborn, and neonatal pneumonia. 
Ultasound studies have been performed for transient tachypnea of the newborn, [14, 15, 16] with the first sonographic characteristic being described in 2007  . In a study comparing 32 newborn infants with radiologic and clinical findings of transient tachypnea of the newborn, a sonographic image called the “double lung point” was described, with the authors reporting a sensitivity and specificity of 100% for the diagnosis of TTN when compared to 60 healthy normal infants—29 with respiratory distress syndrome, 6 with pneumonia, and 5 with atelectasis.  Further studies of this sign have found a sensitivity that ranges from 38%  up to 100%, with specificities close to 100%, as originally described.  .
In a lung ultrasound, B lines are defined as "comet tail" artifacts arising from the pleural line.  The interface between very compact B lines in the inferior pulmonary field, when compared to less compact B lines in the superior lung field, is what is known as as “the double lung point.”  Other characteristics, such as interstitial syndromes or white lungs in patients with severe disease, pleural line abnormalities, and A line disappearance, have also been described. In 20% of cases, an association with pleural effusion was found.  Technical and anatomic concerns are more likely to be raised when ultrasound is used, and negative ethical and medicolegal implications become a matter of concern. 
At this point, ultrasound is not expected to substitute for radiography, and clinicoradiologic correlation is fundamental.