Introduction and objective:
Pneumonia is defined as an acute infection of the lung parenchyma caused by various pathogens. It remains a leading cause of morbidity and mortality in the paediatric population globally. The aim of this study was to disclose most common aetiology of pneumonia among children hospitalized in the University Children’s Hospital in Lublin, Poland, from 2010–2020.

Material and methods:
This retrospective study included 2,250 patients in the age rage from 2–227 months, hospitalized in the Department of Paediatric Pulmonology and Rheumatology of University Children’s Hospital in Lublin from 2010–2020 due to pneumonia. All necessary information were obtained from electronic medical records. According to the International Classification of Diseases Version 10 (ICD-10), patients were divided into 20 groups in terms of aetiology of pneumonia. Subsequently collected data were submitted to statistical calculations.

A seasonality of pneumonia admissions was observed with predominance in the winter. Based on ICD-10 codes, the most common aetiology of pneumonia was unspecified bacterial pneumonia (J15.9) related with 30.2% of all cases. Moreover, based on IgM serology tests, Mycoplasma pneumoniae was the main identified pathogen (18.8% of all cases). Average duration of hospitalization oscillated around 7.4 days; the most common administered antibiotic was amoxicillin + clavulanic acid. Chest imaging was performed in 88.8% of patients.

Pneumonia dominated in the bacterial aetiology of children. Younger groups of children were more prone to the development of pneumonia. In many casus, there were observed difficulties with the identification of an exact pathogen.

Mackenzie G. The definition and classification of pneumonia. Pneumonia (Nathan). 2016; 8: 14.
Mathew JL. Etiology of Childhood Pneumonia: What We Know, and What We Need to Know. Indian J Pediatr. 2018; 85(1): 25–34.
Ramjith J, Roes KCB, Zar HJ, et al. Flexible modelling of risk factors on the incidence of pneumonia in young children in South Africa using piece-wise exponential additive mixed modelling. BMC Med Res Methodol. 2021; 21(1): 17.
Fadl N, Ashour A, Yousry Muhammad Y. Pneumonia among underfive children in Alexandria, Egypt: a case-control study. J Egypt Public Health Assoc. 2020; 95(1): 14. 00043-0.
Hoang VT, Dao TL, Minodier P, et al. Risk Factors for Severe Pneumonia According to WHO 2005 Criteria Definition Among Children <5 Years of Age in Thai Binh, Vietnam: A Case-Control Study. J Epidemiol Glob Health. 2019; 9(4): 274–280.
Rodrigues CMC, Groves H. Community-Acquired Pneumonia in Children: the Challenges of Microbiological Diagnosis. J Clin Microbiol. 2018; 56(3): e01318–17.
Lange J, Kozielski, J, Bartolik, K, et al. The incidence of pneumonia in the paediatric population in Poland in light of the maps of health needs. J Public Health. 2021; 73: 1–9.
Jain V, Vashisht R, Yilmaz G, et al. Pneumonia Pathology. StatPearls (access: 2021.08.04).
Horsky J, Drucker EA, Ramelson HZ. Accuracy and Completeness of Clinical Coding Using ICD-10 for Ambulatory Visits. AMIA Annu Symp Proc. 2018; 2017: 912–920.
Kasundriya SK, Dhaneria M, Mathur A, et al. Incidence and Risk Factors for Severe Pneumonia in Children Hospitalized with Pneumonia in Ujjain, India. Int J Environ Res Public Health. 2020; 17(13): 4637. https://
Orimadegun AE, Adepoju AA, Myer L. A Systematic Review and Metaanalysis of Sex Differences in Morbidity and Mortality of Acute Lower Respiratory Tract Infections Among African Children. J Pediatr Rev. 2020; 8(2): 65–78.
Lange J, Kozielski J, Bartolik K, et al. Analysis of the incidence of acute respiratory diseases in the paediatric population in Poland in the light of the „Health Needs Map”. Adv Respir Med. 2020; 88(3): 204–214.
Lee CH, Won YK, Roh EJ, et al. A nationwide study of children and adolescents with pneumonia who visited Emergency Department in South Korea in 2012. Clin Exp Pediatr. 2016; 59(3): 132–138. https://
Wen Z, Wei J, Xue H, et al. Epidemiology, microbiology, and treatment patterns of pediatric patients hospitalized with pneumonia at two hospitals in China: a patient chart review study. Ther Clin Risk Manag. 2018; 14: 501–510.
Tannous R, Haddad RN, Torbey PH. Management of Community- Acquired Pneumonia in Pediatrics: Adherence to Clinical Guidelines. Front Pediatr. 2020; 8: 302.
González-Coquel S, Escamilla-Arrieta J, Coronell-Rodriguez W, et al. Severity factors of Acquired Pneumonia Community in a children’s hospital in the Colombian Caribbean. Salud Uninorte. 2018; 34(2): 302–314.
Gajewska M, Lewtak K, Scheres J, et al. Trends in Hospitalization of Children with Bacterial Pneumonia in Poland. Cent Eur J Public Health. 2016; 24(3): 188–192.
Mantero M, Tarsia P, Gramegna A, et al. Antibiotic therapy, supportive treatment and management of immunomodulation-inflammation response in community acquired pneumonia: review of recommendations. Multidiscip Respir Med. 2017; 12: 1–19. https://doi. org/10.1186/s40248-017-0106-3.
Nguyen PT, Tran HT, Fitzgerald DA, et al. Antibiotic use in children hospitalised with pneumonia in Central Vietnam. Arch Dis Child. 2020; 105(8): 713–719.
Mathur S, Fuchs A, Bielicki J, et al. Antibiotic use for communityacquired pneumonia in neonates and children: WHO evidence review. Paediatr Int Child Health. 2018; 38(1): 66–75. 20469047.2017.1409455.
Nguyen PTK, Tran HT, Fitzgerald DA, et al. Characterisation of children hospitalised with pneumonia in central Vietnam: a prospective study. Eur Respir J. 2019; 54(1): 1802256. 2018.
Sulley S, Ndanga M. Pediatric pneumonia: An analysis of cost & outcome influencers in the United States. Int J Pediatr Adolesc Med. 2019; 6(3): 79–86.
Hammitt LL, Murdoch DR, Scott JA, et al. Specimen collection for the diagnosis of pediatric pneumonia. Clin Infect Dis. 2012; 54(2): 132–139.
Shim JY. Current perspectives on atypical pneumonia in children. Clin Exp Pediatr. 2020; 63(12): 469–476. cep.2019.00360.
Meyer Sauteur PM, Unger WW, Nadal D, et al. Infection with and Carriage of Mycoplasma pneumoniae in Children. Front Microbiol. 2016; 7: 329.
Chen JR, Zhou XF. A retrospective survey of Chlamydia pneumoniae infection rates in paediatric patients from a single centre in Wuxi, China. J Int Med Res. 2020; 48(10): 1–5.
Fulová M, Kotrbancová M, Bražinová A, et al. Legionnaires› Disease in Pediatric Patients, Control Measures and 5-Year Follow-up. Pediatr Infect Dis J. 2020; 39(11): 990–994. INF.0000000000002781.
O’Grady KAF, Torzillo, PJ, Frawley K, et al. The radiological diagnosis of pneumonia in children. Pneumonia (Nathan). 2014; 5(1): 38–51.
Liszewski MC, Görkem S, Sodhi KS, et al. Lung magnetic resonance imaging for pneumonia in children. Pediatr Radiol. 2017; 47(11): 1420– 1430.
Andronikou S, Lambert E, Halton J, et al. Guidelines for the use of chest radiographs in community-acquired pneumonia in children and adolescents. Pediatr Radiol. 2017; 47(11): 1405–1411. https://doi. org/10.1007/s00247-017-3944-4.
Andronikou S, Goussard P, Sorantin E. Computed tomography in children with community-acquired pneumonia. Pediatr Radiol. 2017; 47(11): 1431–1440.
Stadler JAM, Andronikou S, Zar HJ. Lung ultrasound for the diagnosis of community-acquired pneumonia in children. Pediatr Radiol. 2017; 47(11): 1412–1419.
Franquet T. Imaging of Community-acquired Pneumonia. J Thorac Imaging. 2018; 33(5): 282–294. RTI.0000000000000347.