Pediatric point-of-care ultrasound (P-POCUS) is a skill that enables physicians to use ultrasound technology as an extension of the physical examination to more accurately, efficiently, and safely manage children with acute medical, surgical, and trauma-related conditions. In this chapter, common indications for P-POCUS are briefly reviewed, including torso trauma, lung, skin and soft-tissue, musculoskeletal, and vascular applications.

The focused assessment with sonography in trauma (FAST) scan has been shown to reduce time to operative care, hospital length of stay, use of computed tomography (CT) and hospital costs, as well as improving morbidity in adult trauma patients.^1,2 In the persistently unstable child with torso trauma, FAST similarly allows for the rapid identification and management of intraabdominal hemorrhage.³ On the other hand, most children with intraabdominal injuries do not require surgery, and therefore FAST may serve a different goal. The utility of pediatric FAST in diagnosing intraabdominal hemorrhage versus diagnosing any injury versus clinically important injuries has been studied. The difficulty is in the consistent finding that approximately 15% of patients with torso trauma, for whom trauma code activation criteria were met, and likely some of those in whom it was not, have significant occult injuries. The current gold standard is still CT scanning. When FAST is used in the stable pediatric trauma patient in conjunction with other diagnostic examinations, such as physical examination, liver function test, and/or serial FAST, its performance at identifying clinically important intraabdominal injuries improves significantly.^4–8 A clinical decision rule incorporating serial FAST will likely improve the sensitivity and specificity of algorithms such as that proposed by Holmes et al.,⁹ thereby assuring the appropriate group of injured children have diagnostic imaging while not missing clinically important injuries, with the goal of minimizing unnecessary radiation exposure. One study reported that among patients deemed at moderate risk for intraabdominal injury by treating physicians, its use in trauma may have contributed to 10% to 15% fewer CT scans compared to when not used.¹⁰

The FAST technique uses a low-frequency curvilinear probe to look at the hepatorenal space (Morison’s pouch) in the right upper quadrant, which is the second most dependent part of the supine abdomen and where blood from the pelvis (the most dependent part but very small in volume) and the left upper quadrant drain to and where, when hemorrhage is present, blood will be seen in approximately 85% of cases. Next, the left upper quadrant is scanned, often requiring the user to position the probe more posteriorly and cephalad to locate the spleno–renal interface. This is followed by the pelvic view, in which the bladder–rectum interface in boys, and bladder–uterus and uterus–rectum interfaces in girls, are looked at. Note that physiologic free fluid may occasionally be found on pelvic ultrasound in healthy children,¹¹ and not all positive scans indicate intraabdominal haemorrhage¹²; findings should always be interpreted within the clinical context. Finally, a subxiphoid view of the pericardium is done to evaluate the presence of pericardial effusion, and can also allow one to assess whether there is vigorous or absent cardiac activity to help guide the resuscitation efforts. By looking at these interfaces, one needs to determine whether blood is present or absent; a hypoechoic wedge (black) between the hyperechoic (white) capsules of the mentioned organs is either absent (Fig. 16-1A) or present (Fig. 16-1B–D). If one notes blood above the diaphragm in the right upper quadrant (RUQ) and left upper quadrant (LUQ) views, a hemothorax is identified. Although image interpretation is relatively easy, image acquisition is where most novices have difficulties.

The extended FAST exam (E-FAST), which adds the assessment for lung sliding, often proves very useful given its markedly better accuracy for pneumothorax compared to the supine chest radiograph (sensitivity 98% vs. 75%, respectively).¹³ It is performed by placing the probe across the apex of the supine chest (usually second and third intercostal rib spaces) at the mid-clavicular plane bilaterally (Fig. 16-2) and documenting the presence or absence of lung sliding (also known as lung slide). Absence of lung sliding with a lung point (point at which visceral pleura separates from parietal pleura) allows the clinician to identify a pneumothorax and estimate its size.¹⁴ One noteworthy pitfall is the false positive that a right main stem intubation may cause, in which an absence of lung sliding would be present on the left lung. The presence of lung sliding can also be assessed in M-mode with a “seashore sign” being normal lung sliding and “barcode sign” being that of absent lung sliding. Lastly, some groups have even advocated extending FAST to the major long bones to rapidly assess for presence of fractures to help guide management.⁴

Lung ultrasound (LUS) has emerged as one of the potentially most important applications of P-POCUS. In the sentinel study by Lichtensten,¹⁵ it was shown that LUS could rapidly and accurately narrow the differential diagnosis in adult patients with undifferentiated respiratory failure. An international consensus statement¹⁴ has since been published, and numerous studies have emerged demonstrating the clinical utility of lung ultrasound in its ability to truly “look” inside,¹⁶ especially when compared to the symbolic stethoscope. Children frequently present with undifferentiated respiratory symptoms and undoubtedly not a day goes by in the work of any pediatric clinician where they do not need to exclude pulmonary diseases.

Among febrile children, LUS was shown to be potentially more sensitive than chest radiography for consolidations,¹⁷ with a meta-analysis reporting a high diagnostic accuracy for pediatric pneumonia (sensitivity 96%, specificity 93%).¹⁸ Moreover, compared with physical exam in the Pediatric Emergency Department (PED), LUS performed with a greater diagnostic accuracy than any single or combined clinical finding for pneumonia.¹⁹ One random controlled trial (RCT) demonstrated LUS led to a 40% decrease in chest radiograph utilization,²⁰ and it has been suggested that it may even distinguish between H1N1 influenza (B-lines) from bacterial (consolidation with sonographic bronchograms) pneumonia.²¹ In the context of whiteout lungs on chest radiograph, LUS offers clinicians the ability to rapidly identify whether the underlying pathology is consolidated lung or empyema (Fig. 16-3), the latter of which may require surgical intervention in children with respiratory distress.²²

Among the frequent presentation to the PED of children with undifferentiated respiratory distress and wheeze, clinicians need to determine whether the pathophysiological process is one such as bronchiolitis, asthma, or pneumonia—the management of these conditions each being moderately different. Several studies have reported that B-lines and subpleural consolidations (<1 cm) are frequently found in children with bronchiolitis; the more numerous the abnormalities found in a patient’s lungs seems to correlate with increased disease severity.^23–25 Among wheezing children, LUS may help differentiate the causes of wheeze and more effectively guide the emergency care for children.²⁶

Several other applications for common pediatric conditions exist including differentiating transient tachypnea of the newborn from respiratory distress syndrome in newborns,²⁷ identifying acute chest syndrome in sickle cell anemia,²⁸ identifying pneumothorax¹³ or congestive heart failure,²⁹ as well as helping confirm the appropriate location for endotracheal tube placement³⁰ or aiding in the titration of fluid resuscitation by identifying pulmonary edema.³¹

While all probes can be used to acquire images of the lung, a high-frequency linear ultrasound probe, with harmonic filters turned off and set to a depth of 6 cm, will provide excellent images of the lungs. A six-zone scanning protocol from apex to the base of the lungs can be used with the patient in any position (i.e., supine or sitting in parent’s lap). Each lung is scanned in the longitudinal plane in the midclavicular and midaxillary lines, and posteriorly between the scapula and spine. One starts superiorly and slowly drifts the probe inferiorly all the way down until the diaphragm is visualized. It is important to sweep slowly and pay attention to the following landmarks to avoid common pitfalls: thymus on the medial aspects of the anterior chest, left diaphragm with its underlying spleen or stomach, and right diaphragm with its underlying liver. Identification of these structures helps avoid the false positives that these structures may mimic. A normal lung ultrasound will have A-lines (Fig. 16-4), lung slide, and may have rare B-lines.¹⁶ A positive scan (Fig. 16-4) is defined as follows¹⁴: (i) B-lines (i.e., >3 per intercostal space), which represent interstitial fluid in the subpleural septae; (ii) coalescent B-lines (i.e., white lung) indicative of consolidation; and (iii) tissue-like areas with sonographic bronchograms (sometimes referred to as small subpleural consolidations when under 1–1.5 cm) or hepatization of the lung diagnostic of bacterial pneumonia.

P-POCUS can be used to differentiate between cellulitis and abscess, to determine the location, size, and surrounding structure of an abscess, as well as to diagnose necrotizing fasciitis.^32,33 Clinical examination of skin and soft-tissue infections often reveals erythema, warmth, and tenderness, and can be accompanied by induration and fluctuance. Those clinical findings can be seen in both cellulitis and abscesses and therefore these two entities can be difficult to differentiate clinically. POCUS is highly accurate for identifying abscess in both adults and children (sensitivity 96–97%, specificity 83%),^34,35 even among novices,³⁶ and outperforms clinical examination alone (sensitivity of 75–86%, specificity of 66–80%).^37–40 P-POCUS changed the management decisions (incision and drainage vs. conservation management with antibiotics) for up to 56% of adult patients^38,41 and 22% of pediatric patients.^37,39 The identification of subcutaneous air and fluid along the fascial plane by POCUS revealed a sensitivity of 88% and specificity of 93% for diagnosing necrotizing fasciitis.³³