VASCULAR CAUSES OF ABSENT/SMALL HILUM – 64 SLICE CT
ABSTRACT ID : IRIA - 1198

30 yr old female came with
c/o chest pain,
shortness of breath,
recurrent respiratory tract infections,
anasarca,
CXR:
Small right hemithorax with hyperlucency noted,
Displacement of the mediastinum, to right side
Absent hilar shadow and paucity of vascular markings on right
lung field ,
Prominence of left hilum with pulmonary plethora
Cystic lucencies noted in b/l lower zone
hyperinflation of the left lung.
CT CHEST PLAIN
Right lung shows volume loss
with mediastinal shift to right side
Cystic bronchiectatic changes
noted on right side
CT PULMONARY ANGIOGRAM
Enlarged main pulmonarey artery
(3.8cm) and left pulmonary
artery(2.4cm),
Absent right pulmonary artery
Decreased pulmonary vasculature
noted on right side
Pulmonary plethora on the left side.
Prominence of the left pulmonary
artery branches
The right pleural surface appears
beaded because of the presence of
prominent intercostal arteries
serving as collateral vessels.
Reconstructed ,VR images
Patent ductus arteriosus
Prominent main pulmonary
artery,Left pulmonary artery
DIAGNOSIS
UNILATERAL ABSENCE OF PULMONARY ARTERY (Right pulmonary artery
agenesis)
Associated with
Pulmonary hypertension
Patent ductus arteriosus
UNILATERAL ABSENCE OF PULMONARY ARTERY




UAPA is estimated to be around 1 in 200,000 individuals
The main embryologic defect is an involution of the proximal sixth aortic arch of the
affected side, leading to an absence of the proximal pulmonary artery.
Intrapulmonary vessels and distal portion of the affected pulmonary artery trunk can
develop normally, and blood supply is achieved by systemic collaterals from bronchial,
major aortopulmonary collaterals and other systemic arteries
UAPA is twice as common on the right side
Symptoms
Due to large systemic - pulmonary collaterals from
bronchial,intercostal,internalmammary arteries.
 Hemoptysis – 10% due to rupture of these hypertrophied collaterals.
 Recurrent chest infections
 Pulmonary hypertension - >40yrs.


Left-sided agenesis seems to be more frequently associated with cardiac abnormalities
such as tetralogy of Fallot, septal defects, patent ductus arteriosus, coarctation of the
aorta and transposition of great vessels and therefore early diagnosis and surgical repair
are required during the first year of life.
Patients with isolated right UAPA survive into adulthood with minimal symptoms,
making the diagnosis of such cases more difficult.
UNILATERAL ABSENCE OF PULMONARY ARTERY
The radiologic features
 Small hemithorax,
 Ipsilateral displacement of the mediastinum,
 Absence of the corresponding pulmonary artery,
 Reticular densities along the pleura and within the lung, - due to systemic collateral
circulation.
 Ipsilateral hemidiaphragm elevation with volume loss of the affected lung,
 Absent hilar shadow,
 hyperinflation of the contralateral lung.
CAUSES OF UNILATERAL HYPERLUCENT
HEMITHORAX






Patient positioning
Rotation
Scoliosis
Chest wall defect
Mastectomy
Poland syndrome (absent pectoralis muscle)
Pneumothorax
C/L Pleural effusion
Airway obstruction
Bronchial compression (hilar mass, cardiomegaly)
Endobronchial obstruction with air trapping (foreign body, tumor)
Obliterative bronchiolitis
Swyer-James syndrome
Pulmonary emphysema (asymmetric)
Congenital lobar emphysema
Pneumatocele
Pulmonary vascular cause
Pulmonary embolism
Pulmonary artery hypoplasia
CT – IN UAPA










lack of an identifiable pulmonary artery.
enlarged intercostal arteries serving as collateral vessels to the lung
marked volume loss in the lung.
The pleural surface appears beaded because of the presence of prominent intercostal
arteries serving as collateral vessels.
presence of smaller than usual branches of the inferior pulmonary vein compared with
the normal-sized other side inferior pulmonary vein.
Pulmonary plethora on the other side.
High resolution CT scanning can evaluate the presence of bronchiectasis in cases of
recurrent bronchopulmonary infections.
Pulmonary hypertension
Angiography remains the gold standard for the diagnosis of pulmonary artery
agenesis.
With the development of CT, MRI and magnetic resonance angiographic techniques –it
is rarely performed unless embolization is indicated for massive hemoptysis.
DIFFERENTIAL DIAGNOSIS




Swyer-James-MacLead (SJM) syndrome should be considered in the differential
diagnosis of pulmonary artery agenesis.
Perfusion scintigraphy or pulmonary angiography can be used for the differentiation.
The pulmonary artery is hypoplastic in patients with SJM syndrome, air trapping in
expiration and ipsilateral lung perfusion is absent.
On the other hand,pulmonary artery can not be observed in patients with UAPA, but
peripherally perfusion can be seen via collaterals.
COMPANION CASE





13 year old boy
Cough
Mild dyspnea
h/o ?near drowning
Pulmonary infection in early childhood
Increased lucency on left side
Small hilum on left side compared to right
INSPIRATION
EXPIRATION – Increased lucency on left side due to
Air trapping with mild mediastinal shift to right
CT ANGIOGRAM
Hyperlucenct lung(Left)
 Air trapping on expiration
 Left small hilum
 Diminished Left side pulmonary vascularity
 Normal lung volume
 h/o insult to bronchial tree
Ruling out other conditions of diffuse air trapping

VOLUME RENDERED AND CORONAL
RECONSTRUCTION - shows small left pulmonary
artery.
SWYER JAMES/ MACLEOD SYNDROME
(UNILATERAL EMPHYSEMA,UNILATERAL LOBAR
EMPHYSEMA,UNILATERAL HYPERLUCENT LUN
G)
•
•
•








Swyer-James syndrome (McLeod syndrome)
unilateral post infectious bronchiolitis obliterans in infancy and early childhood.
presence of concentric fibrosis involving the submucosal and peribronchial tissues
of terminal and respiratory bronchioles ,resulting in bronchial narrowing or
obliteration
Radiological features…
Nonspecific
Large lung volume
Small hilum
Increased lung lucency(60%)
Reduced size of peripheral vessels
Central bronchiectasis
HRCT – decreased lung attenuation
-- decreased vessel caliber
-- air trapping
-- bronchiectasis / atelectasis
TAKE HOME MESSAGE
…

Small hemithorax, Ipsilateral displacement of the mediastinum, Absence of the
corresponding pulmonary artery, Reticular densities along the pleura and within
the lung, - due to systemic collateral circulation,Absent hilar shadow,
hyperinflation of the contralateral lung.
UNILATERAL ABSENCE OF PULMONARY ARTERY

Unilateral hyperlucency with evidence of air trapping,reduced size of
pulmonary vessels,small hilum,bronchiectasis and history of some insult
to the bronchial tree during early childhood
SWYER JAMES SYNDROME