Round pneumonia is a type of pneumonia usually only seen in pediatric patients. They are well defined, rounded opacities that represent regions of infected consolidation.
The mean age of patients with round pneumonia is 5 years and 90% of patients who present with round pneumonia are younger than twelve 5. Round pneumonia is uncommon after the age of eight because collateral airways tend to be well developed by this age 2,5.
Patients present with symptoms of chest infection including fever, sweats, and cough. History of infective symptoms is really helpful when excluding other imaging differentials.
The proposed theory as to why children develop round pneumonia and adults do not, relates to the development of inter-alveolar communications and collateral airways. These are called pores of Kohn and canals of Lambert, and when they develop, they allow air-drift between the parenchymal subsegments. In adults, these allow lateral dissemination of infection throughout a lobe, leading to lobar pneumonia. In children, where these have not developed, the limited spread of infection results in round pneumonia 2-4.
The infective agent in round pneumonia is bacterial. There is no specific bacterium that causes round pneumonia, but since Streptococcus pneumoniae is the most common cause of chest infection, it is little surprise that it is the leading cause of round pneumonia 4.
Round pneumonias are round-ish and while they are well-circumscribed parenchymal opacities, they tend to have irregular margins. They most commonly occur in superior segments of lower lobes and in the majority of cases (98%), they are solitary 5.
Air-bronchograms are often present, and helpful in clinching the diagnosis. Interestingly, they are only seen in 17% round pneumonia when they occur in adults 2.
Treatment and prognosis
If round pneumonia is confidently diagnosed, it does not require further investigation. With antibiotic therapy and resolution of symptoms, it does not require follow up.
If a follow-up radiograph is performed, 95% of cases will have resolved at 30 days. Only a minority of cases (5%) progress to lobar pneumonia 5.
In children consider
- pulmonary masses
In adults consider
- pulmonary masses
- round atelectasis
- radiation pneumonitis
- pulmonary pseudotumor
- 1. Dail DH, Tomashefski JF, Hammar SP. Dail and Hammar's Pulmonary Pathology: Nonneoplastic lung disease. Springer Verlag. (2008) ISBN:0387983953. Read it at Google Books - Find it at Amazon
- 2. Wagner AL, Szabunio M, Hazlett KS et-al. Radiologic manifestations of round pneumonia in adults. AJR Am J Roentgenol. 1998;170 (3): 723-6. AJR Am J Roentgenol (abstract) - Pubmed citation
- 3. Bramson RT, Griscom NT, Cleveland RH. Interpretation of chest radiographs in infants with cough and fever. Radiology. 2005;236 (1): 22-9. doi:10.1148/radiol.2361041278 - Pubmed citation
- 4. Stern EJ, White CS. Chest radiology companion. Lippincott Williams & Wilkins. (1999) ISBN:0397517327. Read it at Google Books - Find it at Amazon
- 5. Kim YW, Donnelly LF. Round pneumonia: imaging findings in a large series of children. Pediatr Radiol. 2007;37 (12): 1235-40. doi:10.1007/s00247-007-0654-3 - Pubmed citation