Cranial ultrasound is an excellent and noninvasive tool for brain imaging during the neonatal period and is the study of choice for the initial assessment of neonatal hydrocephalus [8, 9]. Hydrocephalus is the accumulation of fluid within the ventricular system of the brain. The unique presence of open fontanels easily allows one to evaluate for the presence of hydrocephalus using cranial ultrasound. Selection of a probe that fits over the anterior fontanel is recommended. A phased-array probe is commonly selected given its relatively small footprint size. The examination should consist of coronal and sagittal views. For coronal views, the probe is placed directly over the open fontanel with the indicator pointing to the infant’s right. For sagittal views, the probe is rotated so that the indicator now points to the front of the infant’s forehead. The probe should be slowly fanned back and forth in each of these orientations to assess for ventricular enlargement over different sections of the brain. The depth setting is adjusted so that the base of the skull can be seen on the bottom portion of the monitor, a distance of 7–9 cm is a typical starting point. Special precautions should be exercised for this patient population. Given the immature immune systems of neonatal patients, careful attention should be paid to proper hand washing and probe cleansing before and after the ultrasound examination. Given the susceptibility to rapid heat loss, patients should be scanned in a warm environment (or well wrapped with blankets to maintain normal body temperature) and efforts should be made to warm the ultrasound gel before it is applied on the newborn’s head. Figures 9.2 and 9.3 depict changes observed with increasing hydrocephalus in coronal and parasagittal planes.

Intussusception is a common pediatric abdominal emergency, with the highest incidence in children <2 years of age. Clinical presentations can vary and include nonspecific symptoms such as crying episodes, abdominal pain, vomiting, and lethargy. “Currant jelly” stools are a late finding which are suggestive of ongoing bowel ischemia. A high index of suspicion for pediatric intussusception is imperative to minimize associated morbidities when operative management is necessitated. Ultrasound is an accurate and preferred method for the diagnosis of pediatric intussusception [10, 11]. Furthermore, it is an ultrasound application that can be readily learned by novice physician sonographers [12]. A high frequency, linear probe is used to obtain views of all four abdominal quadrants. The scan should begin in the right lower quadrant. With the indicator pointing towards the patient’s right, a transverse view of the psoas muscle should be obtained, as this is a helpful anatomical landmark found in close proximity to the spine (Fig. 9.4). While the patient lays supine, the probe is slowly brought cephalad towards the liver. Upon reaching the right upper quadrant, the probe is rotated 90° with the indicator now pointing towards the child’s head. The probe is now brought across the abdomen in a longitudinal orientation until reaching the left upper quadrant. At this point the probe is again rotated 90° and a transverse scan of the left side of the abdomen down to the left lower quadrant is obtained. Ileo-colic intussusception is most commonly identified by the appearance of a “target sign” in the transverse orientation. In this view the intussusceptum is the part of bowel that is entrapped by the intussuscipiens, which forms the circular outer wall of the intussusception. Normal bowel can have a spectrum of different appearances depending on the amount of air, fluid, fecal material, and ingested matter that is present. Figure 9.5 contrasts the appearance of an ileo-colic intussusception with otherwise normal appearing bowel.

Infantile hypertrophic pyloric stenosis (PS) causes gastric outlet obstruction and presents as persistent, forceful, non-bilious vomiting during the newborn period (usually around 3–12 weeks of age). Palpation of an “olive” during examination of the right upper quadrant may be appreciated, but this finding lacks sufficient sensitivity to reliably rule out the condition. Ultrasound by an experienced operator is the gold standard diagnostic test for PS. A linear probe can be used to obtain longitudinal and transverse views of the pylorus beside the gastric antrum . With the indicator pointing to the infant’s right, a transverse midline view distal to the xiphoid process is a common starting point. Crying infants can be given oral sucrose, a pacifier or be held by their parents to allow for a better study. Administration of Pedialyte or other clear liquid before the ultrasound scan (which displaces air as fluid fills the antrum) and slight rotation of the infant into a right lateral decubitus position will improve one’s ability to visualize the pylorus. The liver acts as an acoustic window and in most cases, a longitudinal view of the pylorus can be found below and adjacent to the liver edge. On longitudinal view, the presence of a “hamburger” may suggest the diagnosis. Ultimately, three measurements are commonly performed: the pyloric muscle thickness (normal measurement is ≤ 3 mm), the pyloric muscle length (normal measurement is ≤ 15 mm), and the pyloric diameter (normal measurement is ≤ 11 mm) [13]. Measurements at or above these cut off values in full term infants support the diagnosis of PS, especially if gastric contents are not visualized to pass the pylorus during sonographic evaluation . A false positive interpretation is possible if the pyloric muscle and channel are imaged at an oblique angle, pylorospasm is present or there is a fluid-filled duodenal bulb. A false negative interpretation is possible if overlying bowel gas creates poor visualization of the pylorus. Figure 9.6 depicts a comparison between the normal anatomy and a hypertrophied pyloric muscle. Note the “hamburger” appearance on longitudinal view.