Friday, November 28, 2014

A 36-year-old woman presented to the accident


A 36-year-old woman presented to the accident and emergency department complaining
of progressively increasing breathlessness over the last 2 weeks. This was accompanied by
a wheeze and cough productive of white sputum. Her exercise tolerance had reduced and
she denied any orthopnoea or chest pain. She had a history of asthma which was usually
well controlled with inhalers and had never previously required a hospital attendance.
There was no other history of note and she denied ever being a smoker. She lived at home
with her husband and two children.
Examination
On examination, her respiratory rate was 22 breaths per minute. She was afebrile and
normotensive with a regular pulse rate of 88 per minute. Her cardiovascular and abdominal
examinations were normal, but on auscultation of her lungs there was a prolonged
expiratory wheeze with reduced air entry at the left base.
A chest radiograph was performed as part of her initial investigations (Figure)


• What radiological abnormality is present?
• What is the most likely cause considering her history?



This patient has left lower lobe collapse. Depending on the airway obstructed, each lobe
collapses in a characteristic way. This was originally described by Benjamin Felson, a
professor of radiology in the United States in 1973. In the case of the left lower lobe,
when there is proximal occlusion, the lobe collapses posteriorly and medially towards the
spine. Lying behind the heart, it assumes a triangular shape with a straight lateral border
being classically described as a ‘sail sign’ on posterior–anterior (PA) chest radiograph as
shown in Figure
.
It usually overlies the cardiac shadow and
can be easily missed on poorly windowed or
under-penetrated films. The collapsed lobe
obscures the left medial hemidiaphragm
and the horizontal fissure swings downwards
with the hilar displaced inferiorly.
Other features to help confirm the diagnosis
would include mediastinal and tracheal
shift towards the side of the collapse, and
possible herniation of the contralateral
lung across the midline from compensatory
hyperinflation. The degree of hilar depression
and compensatory hyperaeration is
variable depending on the degree of collapse.
Less commonly, a stenosing bronchogenic
tumour may be seen as a soft tissue
density overlying the left hilar point.
The causes of lobar collapse are numerous; incidence varies with age and clinical history.
Overall, the commonest cause of collapse is related to a proximal stenosing bronchogenic
carcinoma, and although the majority of lung cancer is seen in men, the incidence in
women is rising. Lung cancer is rarely diagnosed in people younger than 40, but the
incidence rises steeply thereafter with most cases (85 per cent) occurring in people over
the age of 60 with a past medical history of smoking. In ventilated patients, including
neonates, malpositioning of the endotracheal tube can aerate one lung and occlude the
contralateral side, while in infants, collapse related to an inhaled foreign body (e.g. a
peanut) should always be considered. In older children and young adults, the commonest
cause of lobar collapse is as a complication of asthma.


Asthma is a chronic inflammatory disease characterized by reversible airflow limitation
and airway hyperresponsiveness. In response to immunological stimuli, mucus hypersecretion
from goblet cell hyperplasia can cause airway plugging. Proximal occlusion of
a bronchus causes loss of aeration, and as the residual air is gradually absorbed, the lung
volume reduces with eventual collapse. Considering the patient’s age and clinical history,
this is the most likely cause of her left lower lobe collapse.


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