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Radiol Clin N Am 43 (2005) xi – xii Preface Pediatric Chest Imaging Donald P. Frush, MD Guest Editor Children are frightening. Frightening? In nearly all contexts this statement would be indefensible. In medicine, however, children are often frightening. For one thing, clinical evaluation in young children can be more difficult than with adults. In addition, in the acutely ill or injured child, reserve can be limited and appropriate assessment, including imaging evalu-ation, and subsequent care are critically important in improving outcome. Many care providers are not pediatric specialists by practice, and evaluation and treatment of children is less familiar than with adults. Moreover, the spectrum of disorders that affects the pediatric population can be quite different from dis-orders more easily recognized in adults. Often there is an extra layer of emotional concern, or anxiety, because a child is involved. Together, these issues re-inforce the importance of resources which facilitate the diagnosis and care of the sick or injured child. This is especially relevant to chest disorders, because thoracic abnormalities are common in children, and is also relevant to radiologists, because imaging evaluation of the chest is frequently one of the first (or only) tools used after the clinical assessment. Presumably, you are reading this because you are an imager, or interested in imaging evaluation, and because you are caring for children in some capacity. Perhaps you are reading this because, like many of us who have contributed to this work, you understand the importance of being familiar with the imaging evaluation of chest disorders in infants and children. Like many of us, you also understand that current information on many topics is difficult to find, and when available, not a comprehensive resource. This issue of Radiologic Clinics of North America, then, is compiled to provide a contempo-rary resource for those interested in imaging evalua-tion of the pediatric chest. I am fortunate and thankful to have enlisted an internationally recognized panel of pediatric radiolo-gists who bring an additional expertise in thoracic imaging. Because of the many years of expertise, the work reflects not only knowledge, but wisdom regarding the approach and interpretation of chest imaging that only experience brings. Topics covered include focused evaluation of common clinical sce-narios such as pulmonary infection, airway and esophageal disorders, trauma, and chest wall dis-orders; patterns of presentation, such as interstitial lung disease, and lung and mediastinal masses; imaging techniques including ultrasonography and 0033-8389/05/$ – see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.rcl.2005.01.006 radiologic.theclinics.com xii preface CT angiography; as well as special clinical arenas such as chest infection in the immunocompromised child. Together, it is our collective hope that this material will provide you the opportunity to be-come familiar and comfortable with the imaging evaluation of pediatric chest disorders, and in the end, realize that it is not children who are fright-ening...but, rather, our lack of knowledge of and familiarity with pediatric diseases, imaging tech-niques, and their interpretation. Donald P. Frush, MD Professor, Radiology Chief, Division of Pediatric Radiology Department of Radiology McGovern-Davison Children’s Health Center Duke University Health System Erwin Road Box 3808 Durham NC 27710, USA E-mail address: frush943@mc.duke.edu Radiol Clin N Am 43 (2005) 303 – 323 Imaging Evaluation of Congenital Lung Abnormalities in Infants and Children Anne Paterson, MB BS, MRCP, FRCR, FFR RCSI Radiology Department, Royal Belfast Hospital for Sick Children, 180 Falls Road, Belfast BT12 6BE, UK Congenital lung abnormalities include a wide spectrum of conditions and are an important cause of morbidity and mortality in infants and children. This article discusses focal lung abnormalities (eg, congenital lobar emphysema [CLE], congenital cystic adenomatoid malformation [CCAM], bronchopulmo-nary foregut malformations [BPFM], pulmonary sequestrations) and the dysmorphic lung (lung-lobar agenesis–hypoplasia complex). Pulmonary arterio-venous malformations (AVMs) are also included. Thus, anomalies affecting the pulmonary paren-chyma, its arterial supply, and venous drainage are discussed. Disorders of the airways are described elsewhere in this issue. Congenital lobar emphysema Lobar emphysema can either be acquired, or secondary or congenital. CLE refers to progressive overinflation of a pulmonary lobe secondary to air trapping; a ball-valve mechanism allows air into the lobe when there is negative intrathoracic pressure during inspiration, but fails to allow the air out during expiration. Bronchomalacia caused by a deficiency of bronchial cartilage, bronchostenosis, broncho-torsion, obstructive mucosal flaps or mucosal thick-ening, cartilaginous septa, and bronchial atresia have all been described pathologically in CLE lobectomy specimens [1–5]. In others, no cause is found. Secondary lobar emphysema may result if the bron- E-mail address: annie.paterson@royalhospitals.n-i. nhs.uk chus is extrinsically compressed, for example by an enlarged right ventricular outflow tract in patients with congenital heart disease [1,2]. Indeed, there is a reported increase in the incidence of congenital heart disease in association with CLE [2,4]. Lobar over-inflation may also occur with an intraluminal ob-struction, such as an aspirated foreign body. Some authors prefer the expression congenital lobar overinflation to CLE. This is because micro-scopically, CLE specimens do not always demon-strate alveolar destruction. Rather, the alveoli are overdistended but intact [4,6,7]. In a pathologic variant of CLE known as the polyalveolar lobe, the alveoli are normal in size or small, but are increased in number threefold to fivefold [8]. The airways are normal. When the alveoli distend with air, the lobe overinflates because of the sheer number of air spaces. Clinically, most infants with CLE present within the first 6 months of life, with symptoms and signs of respiratory distress. The earlier the child presents, the more severe is the involvement. There is a pre-ponderance of male patients. The chest radiograph remains the primary imaging tool. CLE has a pre-dilection for the upper lobes and right middle lobe. The lower lobes are involved in less than 1% of cases. Bilateral or multifocal involvement is rare [3]. The appearance on the chest radiograph depends on timing: if the radiograph is taken in the first 24 hours of life, the involved lobe is seen to be distended and opaque, because of retained fetal lung fluid. This fluid progressively clears by the tracheobronchial system, lymphatic vessels, and capillary network. The lobe increases in size as it distends with air and demonstrates acinar shadowing, a reticular interstitial 0033-8389/05/$ – see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.rcl.2004.12.004 radiologic.theclinics.com 304 paterson pattern, and finally becomes hyperlucent. The degree of overinflation may cause the overinflated lobe to herniate across the midline. Adjacent lobes are com-pressed, the ipsilateral hemidiaphragm is depressed, and rib spacing is increased. With severe over-distention of a lobe, contralateral lobar compression results and there is cardiomediastinal shift (Fig. 1). Attenuated lung markings are seen in the over-inflated lobe, helping to differentiate it from a pneu-mothorax. In addition, compression of adjacent lobes pushes them cephalad toward the lung apex or caudad toward the diaphragm. With a pneumothorax, the lung collapses around the hilum. Other differential diagnoses include secondary lobar emphysema; congenital lung cysts (including type I CCAM); pneumatoceles; and the Swyer-James syndrome (unilateral hyperlucent lung). The lateral view shows anterior sternal bowing and posterior displacement of the heart. CT scans demonstrate which lobes or segments are involved. The affected lobe is overdistended and hypodense, with attenuated vascular markings (Fig. 2). The septa and vascular structures are at the periphery of the distended alveoli [7]. No cysts or soft tissue are seen. CT is useful to exclude secondary causes of lobar overinflation, such as a vascular ring or a mediastinal mass lesion. In addition to the axial Fig. 1. Congenital lobar emphysema. Chest radiograph of a neonate who developed respiratory distress soon after birth. There is marked overinflation of the right upper lobe, which herniated across the midline. There is compression of the adjacent right middle lobe, contralateral shift of the heart and mediastinum, and widening of the rib spaces on the right side. Fig. 2. Congenital lobar emphysema. CT scan of the chest (lung windows) at the level of the thymus, demonstrating overinflation of the left upper lobe with attenuation of the vascular markings. The mediastinal structures are shifted to the right side and the right upper lobe is compressed. data set, virtual bronchoscopy images may help to define bronchostenosis and exclude an intraluminal foreign body (in an older child). Unsuspected multi-focal disease is identified. Some authors perform ventilation-perfusion scan-ning on infants with less severe symptoms. This shows a matched defect in the affected lobe when Kr-81m is used for the ventilation studies. Adjacent lobes tend to be both ventilated and perfused, despite appearing compressed and atelectatic on the chest radiograph [1,9]. Traditionally, symptomatic patients with CLE undergo lobectomy. Infants are reported to tolerate lobectomy well, with compensatory growth of the remaining lobes [6,10]. Asymptomatic children or those with only minor symptoms are increasingly being managed conservatively [1,2,6]. Follow-up imaging on this group of children has shown a gradual reduction in size of the involved lobe with time. Serial ventilation-perfusion scans have shown ventilation of the lobe to improve and nor-malize. The involved lobe, however, may remain underperfused [9]. Congenital cystic adenomatoid malformation CCAM is thought to result from a failure of normal bronchoalveolar development early in fetal life. There is communication between the individual cysts within the CCAM and also with the tracheo- imaging of congenital lung abnormalities 305 bronchial tree. The classification of Stocker et al [11] has been widely used in both radiologic and pathologic literature. Type I CCAMs: contain one or more cysts mea-suring over 2 cm in diameter, surrounded by multiple smaller cysts. The cysts are lined by ciliated columnar epithelium and their walls contain abundant elastic tissue. Type II CCAMs: contain cysts measuring up to 2 cm in diameter. These cysts are lined with cuboidal or columnar epithelium and are said to resemble dilated bronchioles. Type III CCAMs: usually contain cysts less than 0.5 cm in diameter and are lined by cuboi-dal epithelium. Type I CCAMs are the most common type seen in radiologic practice, constituting approximately 70% of cases [4]. Type II CCAMs make up around 15% to 20% of cases. Type II CCAMs are associated with other congenital anomalies, including renal agenesis and dysgenesis, cardiac malformations, and pulmonary sequestrations (see later) [5,12–15]. Type III CCAMs are rarely seen postnatally and have a poor prognosis. CCAMs occur with equal frequency in the upper and lower lobes, but are less often seen in the right middle lobe. Typically, they are unilobar, but seg-mental CCAMs and lesions involving more than one pulmonary segment or lobe have been reported [6,13,15–17]. In the past, CCAM was usually diagnosed in the early neonatal period, in infants who presented with varying signs of respiratory distress. These days, however, CCAM is increasingly being diagnosed on antenatal ultrasound (US) examinations, where it is seen as an echogenic mass, which may or may not contain cysts [5,17–19]. A CCAM diagnosed in the second trimester of pregnancy, may remain un-changed on subsequent follow-up scans. The lesions, however, can also increase in size and be associated with the development of maternal polyhydramnios or fetal nonimmune hydrops fetalis. The development of nonimmune hydrops fetalis is associated with a poor prognosis [2,5,12,14,18,20]. Antenatal MR imaging may help to evaluate any associated pulmonary hypo-plasia and predict the prognosis [20]. Some ante-natal CCAMs disappear completely on follow-up US examinations [5,14,18–20]. Such infants may or may not be symptomatic at birth. Older children and adults may also present with a CCAM, usually in the context of recurrent respiratory infections. The definitive diagnosis of a CCAM is difficult to make in the latter group of patients, because a pathologic specimen from a healing necrotizing pneumonitic process can resemble a CCAM. CCAMs may also be diagnosed incidentally on a chest radiograph. Postnatally, symptomatic infants with respiratory distress and infants with a previously documented antenatal US anomaly should have a chest radio-graph performed. The radiographic findings are vari-able and correlate with the type of lesion present. Type I CCAMs demonstrate a multicystic lesion, although there can be one dominant cyst (see Fig. 2). Early radiographs may show a water-density mass if the cysts are filled with retained fetal lung fluid; this tends to clear over the first few days of life. In the presence of infection, there may be adjacent alveolar shadowing. Mass effect can cause contralateral mediastinal shift, inversion of the ipsilateral hemi-diaphragm, and compression and atelectasis of both ipsilateral and contralateral pulmonary lobes. The involved lobe may herniate across the midline to the opposite side (Fig. 3). As the cysts fill with air, respiratory symptoms can worsen. Type II CCAMs show cysts of a smaller size (Fig. 4), again with the possibility of lesion heterogeneity if some fetal lung fluid is retained. Type III CCAMs tend to be seen as a homogeneous, soft tissue density mass. The differential diagnosis of a type I or II CCAM in a neonate includes congenital diaphragmatic hernia; a pulmonary sequestration (PS); CLE; and a bron-chogenic (or other BPFM) cyst. The visualization of an intact hemidiaphragm and a normal bowel gas pattern in the upper abdomen helps to exclude the former. If the postnatal chest radiograph is reported as normal in an infant with an antenatally diagnosed lung mass (even one that has reportedly disappeared), then it is advisable for these infants to have a CTscan [5,14,19,20], because many have radiographically occult pulmonary abnormalities. CT scans are helpful to document the involved pulmonary segments or lobes and also confirm the diagnosis in symptomatic infants. CT angiography defines the presence of any systemic arterial vessels supplying the involved lung (a hybrid lesion), an important practical point for those infants in whom surgery is being considered. A CCAM appears as a multicystic mass with CT examination. Fluid-filled cysts and air-fluid levels are easily appreciated. In those presenting with recurrent infections (Fig. 5), then differentiation from a necro-tizing pneumonia is important. The relatively greater degree of overinflation and the lack of visible air bronchograms favor a CCAM [2,4]. The management of patients with CCAM is controversial. Symptomatic neonates with respiratory ... - tailieumienphi.vn
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