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Round pneumonia

Round pneumonia is a type of pneumonia usually only seen in paediatric patients. They are well defined, rounded opacities that represent regions of infected consolidation.

Epidemiology

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. Rounded pneumonia is uncommon after the age of eight because collateral airways tend to be well developed by this age 2,5.

Clinical presentation

Presentation is with symptoms of chest infection and therefore, with symptoms such as fever, sweats and cough. Most of the children who present to Emergency with chest complaints have these symptoms, so they are unhelpful in modification of pre-test probability.  However, history of these symptoms is really helpful when excluding other differentials.

Pathology

The proposed theory about why children develop round pneumonia and adults do not relates to the development of inter-alveolar communication and collateral airways. These are called pores of Kohn and canals of Lambert and when they develop, the allow air-drift between the parenchymal subsegments. In adults, these allow lateral discemination of infection throughout a lobe, leading to lobar pnemonia.  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.

Radiographic features

Plain film

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.

Differential diagnosis

In children consider
In adults consider
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