Chapter 21 – Radiology




Chapter 21 Radiology


James A. Meltzer , Robert Acosta , Dan Barlev , and C. Anthoney Lim



Pediatric Emergency Bedside Ultrasound


Over the past 20 years, bedside ultrasound (BUS) has emerged as an essential tool in the pediatric emergency department. Its applications are designed to answer specific questions, similar to other point-of-care tests. BUS supplements the overall clinical evaluation and does not replace more complete diagnostic imaging performed by radiologists. BUS applications require a minimal amount of training for proficiency and they can significantly expedite time to diagnosis and definitive management. See Table 21.1 for BUS indications and findings.




Table 21.1 Bedside ultrasound indications and findings.






































































































Indications Findings
E-FAST
Blunt or penetrating trauma: identify hemothorax, pneumothorax, pericardial tamponade, hemoperitoneum Significant intrathoracic or intraperitoneal hemorrhage appear as anechoic or hypoechoic stripes seen in potential spaces
Negative E-FAST alone does not rule-out a significant injury
Abdominal ultrasound
Rule-out appendicitis Normal appendix: blind-ended, compressible, tubular structure with a diameter <7 mm, extending from the cecum
Appendicitis: non-compressible structure with a diameter >7 mm, hypoechoic edematous layers with loss of anatomic differentiation
Rule-out intussusception Transverse view: concentric rings (“target or donut sign”)
Longitudinal view: “pseudokidney” or “trident” sign
Transabdominal and/or transvaginal ultrasound
Rule-out ectopic pregnancy IUP: presence of a yolk sac (five weeks) or a fetal pole (six weeks)
Ectopic: may appear as tubal ring, complex adnexal mass, or an extra-uterine gestation sac
Cardiac ultrasound
Pericardial effusion Subxiphoid view: anechoic pericardial fluid between the liver and the heart
Parasternal views: anechoic pericardial fluid posterior to heart but anterior to descending aorta
Pericardial tamponade Right ventricular compression during diastole
Cardiac function Calculate the ejection fraction: EF = (EDD – ESD)/EDD; Poor EF = <30%
Shock Volume overload (cardiogenic, obstructive shock): full IVC with minimal collapse with respiration
Volume depletion (hypovolemic, distributive shock): narrow IVC that completely collapses with respiration
Pulmonary embolus Apical four-chamber view: bowing of the septum and right ventricle > left ventricle
Parasternal short view: flattened intraventricular septum, left ventricle produces a “D” sign
Orthopedic ultrasound
Hip joint effusion Width of the anterior synovial recess >5 mm or the difference in width from the contralateral hip is >2 mm
Elbow joint effusion Normal: posterior humeral fat pad within the protuberances of the olecranon fossa
Effusion: elevated fat pad beyond olecranon fossa protuberances or hypoechoic fluid within the fat pad
Fracture Discontinuity in the normally continuous hyperechoic periosteum
May have an overlying hypoechoic hematoma
Skin ultrasound
Abscess/cellulitis Abscess: hypoechoic fluid collection with hyperechoic walls and increased surrounding vascular flow on color Doppler
Cellulitis: thickened hyperechoic dermal layers with a “cobblestoned” appearance due to interstitial edema and inflammation
Foreign body Hyperechoic anterior surfaces and posterior shadowing
Vein identification Vein: thin-walled, compressible structure with internal color flow
Artery: thick-walled, non-compressible, with pulsatile internal color flow
Regional nerve block Nerve: reticular “honeycombed” structure that exhibits “anisotropy” or variable echogenicity and resolution, depending on the angle of visualization
Tendons: more hyperechoic, will move with muscle activity, but also exhibit anisotropy
Vascular structures: exhibit color flow.


EDD: end diastolic diameter; EF: ejection fraction; ESD: end systolic diameter; IUP: intrauterine pregnancy; IVC: inferior vena cava



Extended Focused Assessment With Sonography for Trauma (E-FAST)


For patients who have sustained blunt or penetrating trauma, a bedside E-FAST is indicated to rapidly identify potentially life-threatening hemoperitoneum, hemothorax, pneumothorax, and pericardial tamponade. The Advanced Trauma Life Support guidelines include the E-FAST as an adjunct to the primary survey and it can be performed simultaneously with resuscitation efforts. The investigation for free fluid can also be useful when evaluating other non-traumatic etiologies (e.g., appendicitis, para-pneumonic effusion, ruptured ectopic, ovarian cyst).


A complete E-FAST consists of four torso views (right upper quadrant, left upper quadrant, subxiphoid, bladder) and bilateral lung views. If possible, place the patient in the Trendelenburg position to allow for free fluid to collect in the upper quadrants, and ask the patient to inhale during the exam to improve visualization.


The normal absence of free fluid in potential spaces is reassuring, demonstrated as a hyperechoic interface between the visceral and parietal peritoneum. Free fluid will appear as an anechoic (i.e., black) collection that settles in dependent areas. Note that a small amount of normal physiologic free fluid may be seen in the retrovesical space in females.


In the setting of trauma, anechoic or hypoechoic stripes seen in potential spaces are indicative of clinically significant intrathoracic or intraperitoneal hemorrhage. These findings may obviate the need for time-consuming computed tomography (CT). Obtain emergent surgical intervention if there is a positive E-FAST in a hemodynamically unstable patient who has not responded to the initial volume resuscitation. In a hemodynamically stable trauma patient, a positive E-FAST indicates the need for further diagnostic testing and surgical consultation. However, a negative E-FAST alone does not rule-out a significant injury.



Abdominal Ultrasound


A point-of-care bedside ultrasound examination can be useful in the evaluation of patients with right lower quadrant pain or unopposed vomiting, in whom there is a suspicion for appendicitis (pp. 241244). A point-of-care ultrasound can also aid in the diagnosis of intussusception (pp. 273274) in infants and toddlers. Obtain prompt surgical and radiologic consultations for official imaging following an abdominal BUS.



Appendicitis

A normal appendix, which can be more difficult to find than an inflamed one, appears as a blind-ended, compressible, tubular structure extending from the cecum, measuring <7 mm in diameter. It often appears as three parallel lines representing a hyperechoic collapsed mucosal lumen surrounded by alternating layers of muscularis and serosa with varying echogenicity. Conversely, appendicitis appears as a non-compressible structure with a diameter >7 mm, with hypoechoic edematous layers with loss of anatomic differentiation. Secondary signs of appendicitis include surrounding free fluid or complex fluid collections, presence of an appendicolith, signs of peritonitis, and localized ileus.



Intussusception

In a negative examination, there will normally be thin multilayered intestinal walls with hypoechoic contents exhibiting peristalsis. Identify intussusception in transverse view as concentric rings (“target or donut sign”) and in longitudinal section as “pseudokidney” or “trident” sign, formed by the edematous bowel walls of the intussusceptum within the intussuscipiens. Color flow often reveals increased vascular flow within the intestinal layers.



Early Pregnancy


A BUS is indicated for any pregnant female with vaginal bleeding and/or abdominal pain, as these symptoms place the patient at risk for an ectopic pregnancy. In a young female who is not receiving fertility treatments, the presence of an intrauterine pregnancy (IUP) on bedside ultrasound effectively rules-out ectopic pregnancy.


If a transabdominal ultrasound is performed, ensure the patient has a full bladder, which will provide optimal images by acting as a “sonographic window” and displacing air-filled bowel. A transvaginal ultrasound is best performed, however, with an empty bladder to allow for a more comfortable examination. Transvaginal ultrasound is more sensitive than transabdominal ultrasound and can identify gestational structures earlier.


Although a gestational sac is usually visualized at four weeks’ gestation on a transvaginal ultrasound, its presence is not sufficient to rule-out ectopic pregnancy. A patient with an ectopic pregnancy may have a pseudo-gestational sac or a decidual cyst that can mimic the anechoic appearance of a gestational sac. Only the presence of a yolk sac (five weeks) or a fetal pole (six weeks) confirms that the patient has an IUP and not an ectopic pregnancy. Obtain obstetrical consultation if the ultrasound does not yield the expected findings by the appropriate post-gestation time. A small amount of intraperitoneal free fluid may be physiologic; however, moderate to large amounts of free fluid in this setting, particularly in Morrison’s pouch, are an ominous finding that is concerning for ectopic rupture.


Ectopic pregnancy, occurring most commonly in the fallopian tube, can occasionally be visualized as a tubal ring, complex adnexal mass, and rarely as an extra-uterine gestation sac complete with a yolk sac, fetal pole, and fetal heart.



Cardiac/Inferior Vena Cava (IVC)


Cardiac ultrasound can help determine the presence of a heartbeat, a pericardial effusion, volume overload (i.e., obstructive or cardiogenic shock) or volume depletion (i.e., distributive or hypovolemic shock), and a pulmonary embolus. It will also assess the overall function of the heart. There are five primary cardiac views: parasternal long view, parasternal short view, subxiphoid view, apical four-chamber view, and inferior vena cava view.



Pericardial Effusion

Anechoic pericardial fluid is often first seen in the most dependent regions. On subxiphoid view, this is the region between the liver and the heart; on the parasternal views, this region is posterior to the heart. To distinguish a pericardial effusion from a pleural effusion in the parasternal long view, note whether the fluid crosses anterior (pericardial) or posterior (pleural) to the descending aorta. Pericardial tamponade is present when the right ventricle becomes compressed during diastole by the pericardial effusion, resulting in obstructive shock.



Cardiac Function

This is best evaluated on the parasternal long view. Often visual inspection of the size of the left ventricle at end systole and end diastole will suffice to evaluate function. Calculate the ejection fraction using the following formula:



Ejection fraction = (end diastolic diameter – end systolic diameter/end diastolic diameter).
Ejection fraction=(end diastolic diameter−end systolic diameter/end diastolic diameter).

An ejection fraction <30% represents poor function.



Shock

Volume overload (i.e., cardiogenic, obstructive shock) has a full IVC that has minimal collapse with respiration versus volume depletion (i.e., hypovolemic, distributive shock) that demonstrates a narrow IVC that completely collapses with respiration.



Pulmonary Embolus

Substantial right heart strain consistent with a pulmonary embolus presents with bowing of the septum and a right ventricle that is larger than the left ventricle on the apical four-chamber view. Similarly, on the parasternal short view, the intraventricular septum will be flattened and the left ventricle produces a “D” sign.

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Sep 22, 2020 | Posted by in EMERGENCY MEDICINE | Comments Off on Chapter 21 – Radiology
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