Technique The high-frequency linear probe, preferably with a large footprint, should be placed in the right lower quadrant in the transverse plane The colon is then traced from right to left, rotating the probe to the longitudinal plane at the level of the transverse colon to maintain a short-axis view of the bowel This focused investigation identifies ileocolic intussusception, the most common type The appearance of the intussusception is noted to be alternating hyperechoic and hypoechoic rings representing the telescoping bowel wall In the center may be noted hyperechoic mesenteric fat and/or hypoechoic lymph nodes which served as lead point ( Video 131.18 ) Sometimes referred to as the target or donut sign, the rings of bowel occupy up to to cm In long axis, the invaginated loops appear similar to the layers of a sandwich, with alternating hyperechoic and hypoechoic layers ( Video 131.19 ) Pitfalls Overlying bowel gas can obscure visualization of the bowel and can prevent identification of intussusception Small bowel intussusception can also occur but is typically self-resolving and often will decompress during observation on ultrasound This entity does not typically require reduction and should be differentiated from ileocolic intussusception Appendicitis Anatomy The normal appendix arises from the cecum in the right lower quadrant In patients with abnormal anatomy this position can be variable Normal intestine appears as alternating hyperechoic and hypoechoic rings representing the histologic layers of the intestinal wall, also known as gut signature A noninflammed appendix is compressible, measuring less than mm Technique With the patient in the supine position, the high-frequency linear or curvilinear probe should be placed in the right lower quadrant to identify the appendiceal body In a patient with significant pain, narcotic analgesia is necessary to perform graded compression to displace overlying bowel gas and facilitate visualization of the underlying bowel In the longitudinal plane, the cecum should be identified, with its fluid-filled haustra and inferior termination into the ileum The appendix will extend from the cecum just proximal to the junction with the ileum In the transverse plane, identification of the psoas muscle laterally and the iliac vessels medially will provide a focused area of investigation for the appendiceal body A noninflammed appendix will have intact gut wall signature with intact peristalsis An acute appendicitis will have notable increase in size measuring mm or greater, be noncompressible, and will often have surrounding periappendiceal fat stranding (Fig 131.21 and Video 131.20 ) FIGURE 131.21 Appendicitis Note the enlarged appendix (arrow ) adjacent to the iliac vessels (IV) and near the psoas muscle (PM) viewed in cross section Pitfalls Obesity often prevents visualization of the appendiceal body on ultrasound In a patient with significant abdominal pain the ultrasound examination can cause pain that limits the ability to perform graded compression This can be mitigated with narcotic analgesia but in a patient with peritonitis, there may still be difficulty in obtaining adequate images Retrocecal appendiceal bodies often require a lateral approach and it may not be feasible to identify with the limited depth of a highfrequency linear probe Finally, the sonographer should be aware of the variable sensitivity of ultrasound in bedside assessment of appendicitis Thus nonvisualization of the appendix should be considered nondiagnostic rather than a negative study PROCEDURAL APPLICATIONS POCUS has the potential to make procedures safer and more efficient by reducing the duration, the number of attempts, and complication rates Ultrasound can be used as an adjunct either before the procedure to identify landmarks and important anatomic structures (static technique) or during the procedure (dynamic technique), allowing for real-time guidance CENTRAL AND PERIPHERAL VENOUS CANNULATION POCUS is an important aid in obtaining intravenous (IV) access for difficult peripheral IV cannulation and for all cases of central venous (CV) access Ultrasound allows clinicians to identify the intended vein for cannulation and to differentiate veins from nearby anatomic structures such as arteries and nerves Of note, most superficial peripheral veins are not paired with arteries However, deeper veins like the brachial veins and veins used for central access, such as the femoral and internal jugular, have arteries alongside them Central Venous Cannulation Central vascular access is among the most commonly performed ultrasoundguided procedures The Agency for Healthcare Research and Quality has stated that ultrasound for CV access is a clear opportunity for safety improvement and listed it as one of the “Top 11 Highly Proven” patient safety practices It is considered standard of care according to multiple subspecialty policy statements and published international evidence-based consensus recommendations In adults, POCUS for central line placement increases success rates and decreases procedural complications Similar reports exist in the pediatric population In a recent meta-analysis, US-guided CV placement decreased the number of attempts and improved success rates The evidence in both the adult and pediatric population, along with the generalizability of the procedure, suggests that ultrasound is a necessary skill for the practitioner who places CV lines in children Technique The sonographic technique for identifying vessels is similar whether placing a peripheral IV or a CV catheter A high-frequency linear transducer is the probe of choice Relevant anatomy for the particular site chosen (femoral, internal jugular) should be reviewed Preprocedure steps are important to maximize success, including adjusting the height of the bed, positioning the patient, positioning the ultrasound machine, and having equipment and extra personnel ready for assistance For CV access, aseptic technique should be used with sterile probe covers and sterile gel (if probe covers are unavailable, a sterile glove will suffice) Prior to performing the procedure, the intended target vein should be identified and confirmed first in the transverse plane and then in the longitudinal plane On ultrasound, veins are characterized by their easy compressibility, color flow, and Doppler waveforms Placing gentle pressure on the probe, the walls of vein should collapse In contrast, arteries will pulsate and the walls of the arteries will resist collapsing when compressed ( Videos 131.21 and 131.22 ) Both veins and arteries have characteristic patterns when assessed with color Doppler ( Video 131.23 ) Once the vein is identified, the depth to the center of the vein should be measured When the needle is inserted into the skin, it is traveling along the hypotenuse of a right triangle, and the distance it must traverse before hitting the vein should be calculated In the static approach, once the vasculature and surrounding anatomy are imaged, the position of the vein should be marked on the skin at two points along the path of the vessel The ultrasound probe is then set aside and the procedure continues using the landmarks identified with ultrasound, but without active ultrasound assistance This method does improve success rates, although complications are reduced further when using dynamic ultrasound The dynamic method uses ultrasound in real time to visualize the needle puncturing the vein It is important that the ultrasound machine be positioned in front of the proceduralist, making direct visualization possible The transducer marker should face to the left, the same direction as the marker on the screen This is critical when redirecting the needle; as the needle is moved toward the left of the probe, it moves toward the left side of the screen ... exist in the pediatric population In a recent meta-analysis, US-guided CV placement decreased the number of attempts and improved success rates The evidence in both the adult and pediatric population,