[10] Han BK, Babcock DS, Oestreich AE. Normal thy- mus in infancy: sonographic characteristics. Radiol- ogy 1989;170:471– 4. [11] Ben-Ami TE, O’Donovan JC, Yousefzadeh DK. Sonography of the chest in children. Radiol Clin North Am 1993;31:517– 31. [12] Sklair-Levy M, Agid R, Sella T, et al. Age-related changes in CT attenuation of the thymus in children. Pediatr Radiol 2000;30:566– 9. [13] Takahashi K, Inaoka T, Murakami N, et al. Characteri- zation of the normal and hyperplastic thymus on chemical-shift MR imaging. AJR Am J Roentgenol 2003;180:1265– 9. [14] Hibi S, Todo S, Imashuku S. Thymic localiza- tion of gallium-67 in pediatric patients with lym- phoid and nonlymphoid tumors. J Nucl Med 1987; 28:293–7. [15] Handmaker H, O’Mara RE. Gallium imaging in pediatrics. J Nucl Med 1977;18:1057. [16] Johnson PM, Berdon WE, Baker DH, et al. Thymic uptake of gallium-67 citrate in a healthy 4 year old boy. Pediatr Radiol 1978;7:243–4. [17] Michigishi T, Mizukami Y, Shuke N, et al. Visualiza- tion of the thymus with therapeutic doses of radio- iodine in patients with thyroid cancer. Eur J Nucl Med 1993;20:75– 9. [18] Fletcher BD. Thymic concentration of radiolabeled octreotide. J Nucl Med 1999;40:1967. [19] Connolly LP, Connolly SA. Thymic uptake of radio- pharmaceuticals. Clin Nucl Med 2003;28:648– 51. [20] Patel PM, Alibazoglu H, Ali A, et al. Normal thymic uptake of FDG on PET imaging. Clin Nucl Med 1996;21:772– 5. [21] Nakahara T, Fujii H, Ide M, et al. FDG uptake in the morphologically normal thymus: comparison of FDG positron emission tomography and CT. Br J Radiol 2001;74:821– 4. [22] Alibazoglu H, Alibazoglu B, Hollinger EF, et al. Normal thymic uptake of 2-deoxy-2[F-18]fluoro-D- glucose. Clin Nucl Med 1999;24:597– 600. [23] Saggese D, Compadretti GC, Cartaroni C. Cervi- cal ectopic thymus: a case report and review of the literature. Int J Pediatr Otorhinolaryngol 2002;66: 77 – 80. [24] Malone PS, Fitzgerald RJ. Aberrant thymus: a mis- leading mediastinal mass. J Pediatr Surg 1987;22:130. [25] Saade M, Whitten DM, Necheles TF, et al. Pos- terior mediastinal accessory thymus. J Pediatr 1976; 88:71 – 2. [26] Baysal T, Kutlu R, Kutlu O, et al. Ectopic thymic tissue: a cause of emphysema in infants. Clin Imag- ing 1999;23:19– 21. [27] Bach AM, Hilfer CL, Holgersen LO. Left-sided posterior mediastinal thymus: MR imaging findings. Pediatr Radiol 1991;21:440– 1. [28] Bar-Ziv J, Barki Y, Itzchak Y, et al. Posterior medi- astinal accessory thymus. Pediatr Radiol 1984;14: 165 – 7. [29] Cohen MD, Weber TR, Sequeira FW, et al. The diag- nostic dilemma of the posterior mediastinal thymus: CT manifestations. Radiology 1983;146:691–2. [30] Rollins NK, Currarino G. Case report: MR imaging of posterior mediastinal thymus. J Comput Assist Tomogr 1988;12:518 – 20. [31] Slovis TL, Meza MP, Kuhn JP. Aberrant thymus: MR assessment. Pediatr Radiol 1992;22:490– 2. [32] Kuhn JP. Pediatric thorax. 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Malignant mediastinal neo- plasms in children. Vestn Khir Im I I Grek 2003;162: 46 – 8. [46] Takeda S, Miyoshi S, Akashi A, et al. Clinical spectrum of primary mediastinal tumors: a compari- son of adult and pediatric populations at a single Japanese institution. J Surg Oncol 2003;83:24–30. [47] Asakawa H, Kashihara T, Fukuda H, et al. A pa- franco et al350 Imaging in Immunocompetent Children Who Have Pneumonia Lane F. Donnelly, MD a,b, * a Department of Radiology, Cincinnati Children’s Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229 – 3039, USA b Radiology and Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA In 1994, the year that I was a pediatric radiology fellow at Cincinnati Children’s Hospital, there was a dramatic increase in the number of children hospi- talized with complications related to bacterial pneu- monia. This included an increase in the number of purulent lung complications, such as cavitary ne- crosis, and an increase in the number of empyemas as compared with years past. There was a lot of speculation at the time as to why there had been a sudden increase in the frequency of children with complications related to pneumonia. Some speculated that it was related to an increased frequency of anti- biotic-resistant streptococcal pneumonia infections. Others speculated that there had been a strain of in- fluenza A virus that went through the community and was associated with injury to the respiratory mucosa resulting in children who were predisposed to de- veloping complications when they were infected with bacterial pneumonia. In subsequent years, however, there again were increasing numbers of children hos- pitalized for complications related to pneumonia each year. This trend continues today. I became involved in several projects reporting on our experience at Cincinnati Children’s with the use of CT in these children with pneumonia-related complications [1–5]. Subsequently, I have been in- volved in writing several review articles on the roles of imaging in children with pneumonia [6,7].In preparation for writing this article, I have done a recent literature search and, unfortunately, very little has changed in the past 10 years concerning what is known about the performance of imaging studies in the management of children with pneumonia. Many of the areas of controversy, such as how aggressively parapneumonic effusion should be managed, are still without definitive and agreed on plans of action. In this article, the roles of imaging in children with pneumonia are discussed. The contents of this article apply to when immunocompetent and previ- ously healthy children develop pneumonia or its complications. The indications for imaging and implication of the findings at imaging are completely different in children who are immunodeficient or have underlying medical conditions, such as sickle cell anemia or cystic fibrosis. A discussion of those chil- dren is beyond the scope of this article. The following topics are covered concerning the roles of imaging in the management of pneumonia: evaluation for possi- ble pneumonia, determination of a specific etiologic agent, exclusion of other pathology, evaluation of the child with failure of pneumonia to clear, and evalua- tion of complications related to pneumonia. Evaluation for possible pneumonia Respiratory tract infections are the most common cause of illness in children and one of the most common indications for imaging in children. Chest radiographs are often obtained as part of the evalua- tion to determine whether or not a child is likely to have bacterial pneumonia. At first, it seems that 0033-8389/05/$ – see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.rcl.2004.11.001 radiologic.theclinics.com * Department of Radiology, Cincinnati Children’s Hos- pital and Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229-3039. E-mail address: Lane.Donnelly@cchmc.org Radiol Clin N Am 43 (2005) 253 – 265 Thoracic Disorders in the Immunocompromised Child Caroline L. Hollingsworth, MD Division of Pediatric Radiology, Department of Radiology, Duke University Health System, 1905 McGovern-Davison Children’s Health Center, Box 3808, Erwin Road, Durham, NC 27710, USA The population of children afflicted with primary or secondary immunodeficiencies is in evolution. The primary immunocompromised host was first de- fined over 50 years ago when Bruton [1] discovered X-linked agammaglobulinemia (XLA), a congenitally acquired humoral immunodeficiency. Delineation and description of over 100 other primary immunodefi- ciency syndromes has ensued, which includes a diverse group of conditions caused by abnormalities in antibody production, cell-mediated immunity, or the phagocyte and complement activity. Although the number of children afflicted with primary immuno- deficiencies remains relatively small, the impact of such diseases on each child is considerable. Second- ary immunodeficiencies in childhood may result from infection with HIV or can be caused by chemo- therapy, radiotherapy, or immunosuppressive therapy aimed at treating childhood malignancies; transplant rejection; rheumatologic disorders or inflammatory or infectious diseases; and any state of debilitation. Moreover, the development and success of many ag- gressive cytotoxic regiments and immunosuppressive therapies for children with cancer or autoimmune disorders and the increasing use of stem cell or bone marrow transplantation (BMT) have increased the number of immunocompromised children. This complex and varied population of immunocompro- mised children is at high risk for pulmonary com- plications related to both their underlying disease state and to various treatment regimes. Although infections obviously account for many complica- tions, immunocompromised children are also at high risk for development of many other types of tho- racic complications. These include primary and secondary thoracic malignancies and nonmalignant lymphoid proliferation, noninfectious pneumonias, bronchiolitis obliterans, pulmonar y edema, graft- versus-host disease (GVHD), radiation injury, and pulmonary thromboembolism. Specific thoracic complications vary according to the child’s underlying immune status and specific treatment protocols. As such, the type of infection or other disease states encou ntered depends on the child’s type of immunologic abnormality, severity of immunologic deficit, therapeutic interventions, and environmental exposures [2]. Although this discus- sion does not include all immunodeficiencies, the common primary immunodeficiencies and secondary immuno compromised states of childhood are ad- dressed with emphasis on the mechanism of the dis- order; imaging features of thoracic complications; and, where appropriate, imaging surveillance strategies. Primary immunodeficiencies Humoral immunodeficiencies Humoral immunodeficiencies are the most com- monly encountered type of primary immunodefi- ciency, accounting for over 70% of all primary immunodeficiencies [3 – 5]. This diverse group of disorders is characterized by defective antibody pro- duction causing increased susceptibility of affected individuals to recurrent pyogenic infections, par- ticularly caused by encapsulated bacteria, such as Haemophilus influenzae, Streptococcus pneumoniae, and Staphylococci. Typical manifestations include 0033-8389/05/$ – see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.rcl.2005.01.003 radiologic.theclinics.com E-mail address: holli016@mc.duke.edu Radiol Clin N Am 43 (2005) 435 – 447 . thymus on chemical-shift MR imaging. AJR Am J Roentgenol 2003; 180 :1265– 9. [14] Hibi S, Todo S, Imashuku S. Thymic localiza- tion of gallium-67 in pediatric patients with lym- phoid and nonlymphoid. emission tomography and CT. Br J Radiol 2001;74 :82 1– 4. [22] Alibazoglu H, Alibazoglu B, Hollinger EF, et al. Normal thymic uptake of 2-deoxy-2[F- 18] fluoro-D- glucose. Clin Nucl Med 1999;24:597– 600. [23]. Nucl Med 1 987 ; 28: 293–7. [15] Handmaker H, O’Mara RE. Gallium imaging in pediatrics. J Nucl Med 1977; 18: 1057. [16] Johnson PM, Berdon WE, Baker DH, et al. Thymic uptake of gallium-67 citrate