11: Imaging Studies

COMMON RADIOLOGIC TECHNIQUES

I. RADIOGRAPHIC EXAMINATIONS

The need for radiographs must always be weighed against the risks of exposure of the neonate to radiation (eg, 3–5 mrem per chest radiographic view). The infant's gonads should be shielded as much as possible, and any person holding the infant during the x-ray procedure should also wear a protective shield. For the usual vertically oriented radiographic exposure, personnel need to be only 1 ft outside the zone of exposure.

1. Chest radiographs

   1. Anteroposterior (AP) view. The single best view for identification of heart or lung disease, verification of endotracheal tube and other line positions, and identification of air leak complications of mechanical ventilation, such as pneumothorax.

   2. Cross-table lateral view. Of limited diagnostic value except to determine whether a pleural chest tube is positioned anteriorly (best for drainage of a pneumothorax) or posteriorly (best for drainage of a pleural fluid collection).

   3. Lateral decubitus view. Best at evaluating for a small pneumothorax or a small pleural fluid collection, as either can be difficult to identify on the AP view. For example, if a pneumothorax is suspected, a contralateral decubitus view of the chest should be obtained. An air collection between lung and chest wall will be visible on the side on which the pneumothorax is present. By contrast, for pleural fluid identification, the same side should be placed down (ipsilateral decubitus). The lateral decubitus view may not be safely obtainable in unstable infants.

   4. Upright view. Rarely used in the neonatal intensive care unit (NICU), but can identify abdominal perforation by showing free air under the diaphragm.

2. Abdominal radiographs

   1. AP view. The single best view for diagnosing abdominal disorders such as intestinal obstruction or mass lesions and checking placement of support lines such as umbilical arterial and venous catheters and intestinal tubes.

   2. Cross-table lateral view. Helps diagnose abdominal perforation, but the left lateral decubitus view is better for this purpose. Abdominal perforations may be missed on the AP and cross-table lateral views if the amount of intraperitoneal air is limited or if the segment of perforated bowel contains only fluid.

   3. Left lateral decubitus view. (With the infant placed left side down.) Best for diagnosis of intestinal perforation. Free intra-abdominal air resulting from bowel perforation will be visible as an air collection between the liver and right lateral abdominal wall.

3. Babygram. A radiograph that includes the whole body or just the chest and abdomen (thoracoabdominal babygram) on a single image. It is most commonly ordered for line placement.

4. Barium contrast studies (barium swallow or barium enema). Barium sulfate, an inert compound, is not absorbed from the gastrointestinal (GI) tract and results in little or no fluid shift.

   1. Indications. The use of barium as a contrast agent is recommended for the following:

      1. GI tract imaging. Barium enema is used to rule out lower intestinal tract obstruction from a variety of causes.

      2. Suspected H-type tracheoesophageal fistula (TEF) without esophageal atresia (type E). Most ...