I think that when I was taught as a medical student, the auscultation findings in the chest were over-emphasised. The reality is that these can be misleading.
First of all, the presence of focal findings in the chest is common even in the absence of LRTI.
- The infant or child with URTI will often have crepitations that can be heard in one or more places in the chest. These may be transmitted sounds or due to secretions. Breath sounds will be normal throughout. In the absence of abnormal breathing, these crackles are not good evidence for LRTI. Often, these noises go away or move around if re-examined, especially after a cough.
- The infant or child with a wheeze may have crepitations and variation in the loudness of breath sounds in different parts of their chest. Bacterial LRTI does not usually cause wheeze but wheezy problems often lead to focal findings. The clue that the problem is not a LRTI is that the child is systemically well. The basic rule is this: if a child with a wheeze does not look ill enough to be admitted to hospital, they do not have a bacterial LRTI. Bronchiolitis and viral-induced wheeze are all the explanation needed for abnormal breathing. If a child had one of these and a pneumonia, they would really be in difficulty.
- The child with viral-induced wheeze may have no wheeze to further complicate things. Consider a trial of beta-agonist inhalers in well child with respiratory distress, especially if there is a past history of wheeze.
Secondly, the absence of focal findings in the chest is a relatively common scenario in the child with LRTI.
- Auscultation and percussion in infants and small children is difficult. Chests are small and there is always the possibility that the area of abnormality will be missed. The child with cough, fever and abnormal breathing should be presumed to have a LRTI unless proved otherwise.
- Not all LRTIs even produce focal signs. Sometimes a segment of a lobe is all that is infected (known radiologically as a round pneumonia) and it is quite common in such cases for the only clues to be the combination of unwellness and respiratory abnormality.
Nor should we rely on chest X-ray (CXR) to make the decision for us. The sensitivity and specificity of CXR as a way to diagnose pneumonia in children is too poor to justify using radiation when the diagnosis should be made clinically. The BTS guidelines for community-acquired pneumonia in children and the Clinical Practice Guidelines by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America both recommend that CXR and blood tests are routinely avoided. (1,2)