Bronchiolitis

Definition/diagnostic criteria Bronchiolitis is an acute lower respiratory tract infection that primarily affects infants, usually under one year of age. It is characterised by a viral infection leading to inflammation and congestion of the bronchioles. It is typically defined as a clinical diagnosis primarily based on the history and examination findings of a young child with a coryzal prodrome followed by persistent cough, tachypnoea and wheezing or crackles on auscultation.

Epidemiology Bronchiolitis is common, with most children being infected at least once by the age of two. In the UK, it is the most common cause of hospital admission in infants, particularly during the winter months. Respiratory syncytial virus (RSV) is responsible for up to 75% of cases.

Diagnosis
Clinical features: Diagnosis is mainly clinical. Initial symptoms include a runny nose, cough, and possibly a fever. As bronchiolitis progresses, increased respiratory effort and feeding difficulties may develop. Clinical signs include tachypnoea, chest wall recession, and wheezing or crackles on auscultation. Fever is usually less than 39◦C (which may help to distinguish it from pneumonia, where the fever may be higher than this).

Investigations and typical abnormalities: Investigations are not routinely recommended in primary care as the diagnosis is clinical, although, if available, pulse oximetry should be performed (with O2 saturation of less than 92% being a red flag).

However, if hospital admission is required, investigations might include pulse oximetry to check oxygen saturation levels and, in some cases, chest X-rays. That said, chest X- rays are not routinely performed in babies or children with bronchiolitis, because changes on X‑ray may mimic pneumonia and so can lead to inappropriate use of antibiotics.

Treatment Treatment is mainly supportive as bronchiolitis is usually a self-limiting disease. Consider urgent referral for children with respiratory distress, hypoxia, difficulty feeding or dehydration.

Management in primary care includes advising parents about fluid intake to prevent dehydration and explaining the natural course of the disease.

Prognosis The prognosis for bronchiolitis is generally good, with most children recovering within two to three weeks. However, a small number of infants, particularly those with underlying conditions such as congenital heart disease or prematurity, may have severe disease and require hospitalisation. Long-term respiratory problems such as recurrent wheezing or asthma have been associated with severe bronchiolitis in infancy.