Pitfalls The rib shadows often obstruct visualization of the kidney; slight probe rotation can mitigate this effect The left kidney often requires a more posterior and superior approach than expected If localization remains difficult, having the patient breathe deeply often causes inspiration to push the kidney into view FIGURE 131.18 A, B, C: Longitudinal section of the left kidney reveals nephrolithiasis (arrows ) in the superior and inferior poles in the same patient (Images courtesy of Christi Tumblin, Zanesville, OH In: Kawamura D, Lunsford B, eds Diagnostic Medical Sonography 3rd ed Philadelphia, PA: Lippincott Williams & Wilkins; 2012 With permission.) FIGURE 131.19 Full bladder measured in two different planes Bladder Ultrasound Bladder ultrasound is performed for a variety of reasons For the child who has not voided for a prolonged period, assessing bladder size can inform the practitioner if there is a problem with urinary retention More commonly, bladder ultrasound is done prior to bladder catheterization or suprapubic aspiration to assess volume of urine and thereby improve success rates It may be used dynamically as well to guide needle placement and improve success rates of suprapubic aspiration Technique The same approach as the pelvic view of the FAST examination is used when performing a bladder ultrasound A high-frequency linear probe or low-frequency abdominal probe may be used A full bladder will appear as a well-circumscribed, fluid-filled (anechoic) structure within the pelvis Once the bladder is identified, it should be measured in at least two planes (Fig 131.19 ) Although studies differ with respect to exact measurements, generally speaking if the wall-to-wall distance measures greater than cm in both planes, catheterization or suprapubic aspiration will likely be successful Pediatric Abdomen Pediatric patients often present to the ED for evaluation of vomiting and/or abdominal pain In infants less than months of age, there is often concern for hypertrophic pyloric stenosis (HPS), requiring ultrasound for definitive diagnosis In the toddler age group, colicky abdominal pain with associated emesis can be signs of intussusception, a pathology that is also diagnosed with sonography In children of all ages, abdominal pain that is localized to lower right side of the abdomen raises concern for appendicitis Ultrasound has become the first-line diagnostic modality for appendicitis but sensitivity depends on patient characteristics and sonographer skill Recent literature has demonstrated the ability of pediatric emergency medicine providers to identify pyloric stenosis, intussusception, and appendicitis on bedside sonography Hypertrophic Pyloric Stenosis Anatomy The gastric outlet in infants abuts the medial portion of the hepatic contour The pyloric channel connects the antrum of the stomach to the first portion of the duodenum and is surrounded by muscle The position of the pylorus is dependent upon the fullness of the stomach, but is typically adjacent to the gall bladder and anteromedial to the right kidney Technique A high-frequency linear probe, preferably with a large footprint, positioned on the upper abdomen to the right of midline, will allow visualization of the pylorus as it extends from the stomach, deep to the liver The probe is oriented longitudinally with the marker angled slightly toward the right shoulder for the short-axis view and then rotated 90 degrees in the transverse plane to obtain the long-axis view In the long axis, the inner channel appears as a narrow canal flanked by the linear hyperechoic walls that are surrounded by the hypoechoic muscular pylorus (Fig 131.20 ) As the pylorus thickens, it often extends superiorly toward the gall bladder and when the channel has become obstructed, absence of passage of liquids can be seen as retrograde peristalsis into the stomach Measurements of the pylorus should be performed to assess for hypertrophy with an abnormal muscle thickness measuring greater than mm and an abnormal channel length measuring greater than 17 mm Pitfalls Infants with an air- and liquid-filled stomach often have a gastric outlet that is pushed beyond midline to the right side of the abdomen, and often the pylorus dives posteriorly In this setting, rotating the infant to the right decubitus position can improve visualization Allowing the child to feed clear fluids during the examination facilitates identification of the pylorus by providing an excellent acoustic window If available, warm gel will improve probe contact as infants are particularly intolerant of cold gel FIGURE 131.20 Longitudinal view of pylorus The “A” calipers measure the muscle thickness and the “B” calipers measure the channel length Intussusception Anatomy Intussusception occurs when a loop of bowel, the intussusceptum, advances distally and, through peristalsis, becomes trapped in the distal bowel lumen, the intussuscipiens The bowel wall becomes edematous and intestinal obstruction ensues The most common site of intussusception is the ileocolic region of the bowel Mesentery, vascular supply, and lymph tissue accompany the invaginated loop and, as entrapment persists, ischemia develops and the bowel is at risk of perforation Small bowel intussusceptions can occur but are typically selfresolving ... characteristics and sonographer skill Recent literature has demonstrated the ability of pediatric emergency medicine providers to identify pyloric stenosis, intussusception, and appendicitis on... cm in both planes, catheterization or suprapubic aspiration will likely be successful Pediatric Abdomen Pediatric patients often present to the ED for evaluation of vomiting and/or abdominal