Imaging of the Neonate: Preterm Infant

Preterm birth is birth before 37 weeks’ gestational age. The incidence of preterm birth is approximately 1 in 10 births in the United States. The imaging of a preterm infant is not uncommon, and especially in the neonatal period, the radiologist plays a crucial role in the diagnosis of common complications related to preterm birth. Through a system-based approach, this chapter will review key imaging diagnoses commonly seen in the preterm infant.

Is This Neonate Preterm?

When evaluating any neonatal radiograph, a helpful initial step is to determine whether the neonate is preterm. Signs of prematurity include overall reduction in subcutaneous fat and lack of humeral head ossification. Humeral head ossification is almost never present before 38 weeks’ gestational age.

Lines and Tubes in the Neonatal Intensive Care Unit

Umbilical Venous Catheter

Umbilical venous catheters (UVCs) are used in critically ill neonates for venous access for administration of intravenous fluids, parenteral nutrition, blood products, and medical medications, because peripheral and conventional central venous catheters are difficult to place. The typical course of the UVC is from the umbilical vein superiorly into the left portal vein, after which it courses through the ductus venosus into the inferior vena cava. The ideal positioning of the UVC is at the inferior vena cava–right atrial junction ( Fig. 18.1 ).

Fig. 18.1, Appropriate positioning of an umbilical venous and umbilical arterial catheter.

Because of lack of imaging guidance during UVC placement, misplacement is not uncommon ( Fig. 18.2 ). Complications of UVC misplacement include hepatic hematoma and necrosis in the setting of an intrahepatic placement of a UVC ( Fig. 18.3 ), right or left atrial perforation, or umbilical vein perforation resulting in extravasation or hemoperitoneum ( Fig. 18.4 ). Thrombosis in the inferior vena cava may occur even in an appropriately positioned UVC.

Fig. 18.2, Umbilical venous catheter malposition.

Fig. 18.3, Umbilical venous catheter malposition.

Fig. 18.4, Umbilical venous catheter malposition.

Umbilical Arterial Catheter

Umbilical arterial catheters (UACs) are used in neonates for blood pressure monitoring, blood sampling, and infusion of fluids and medications. The course of the UAC is from one of the two umbilical arteries inferiorly into the right or left internal iliac artery, after which it ascends through the common iliac artery into the aorta. A UAC may be positioned with the tip between T6 and T9 (high UAC) or L3 and L5 (low UAC) to avoid the major aortic branches vessels (see Fig. 18.1 ). Complications of UACs include aortic thrombus, embolic events, and renal artery thrombus, which can result in hypertension or renal infarction.

Chest

How to Approach Lung Opacities in the Preterm Infant?

In the immediate neonatal period, particularly on the initial chest radiograph, surfactant deficiency syndrome is the most common diagnosis. Other diagnoses and superimposed conditions, such as infection, pulmonary edema, masses, and congenital anomalies, may also be present in preterm infants (see discussion in Chapter 19 ).

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