Joints

2. Findings and Diagnosis

 

Pectus Excavatum and Its Chest X-Ray (CXR) Appearance

• Definition

  • Congenital deformity of the anterior chest wall characterized by posterior displacement of the sternum.
  • Can cause compression of the heart and lungs, leading to functional impairment in severe cases.

• CXR Findings

  • Cardiomediastinal shift to the left
    • The heart is displaced due to sternal depression, pushing it toward the left hemithorax.
  • Increased density along the right heart border
    • Caused by compression of the adjacent lung parenchyma between the depressed sternum and the heart.
    • Can sometimes mimic right middle lobe consolidation or a mediastinal mass.
  • Widened mediastinum appearance
    • The altered shape of the chest wall can create the illusion of an enlarged cardiac silhouette.
  • Horizontal orientation of the ribs
    • May be more prominent in severe cases.
  • Flattening or posterior angulation of the sternum (better seen on lateral view).

• Clinical and Imaging Considerations

  • Mild cases are often asymptomatic and detected incidentally on imaging.
  • Severe cases may cause restrictive lung disease, cardiac compression, or exercise intolerance.
  • CT imaging is preferred for quantifying the severity using the Haller index and assessing compression of thoracic structures.

• Diseases Associated with Pectus Excavatum in Humans:
  • Connective tissue disorders
    • (e.g., Marfan syndrome, Ehlers-Danlos syndrome)
      Congenital syndromes (e.g., Noonan syndrome, Poland syndrome)
  • Neuromuscular disorders
    • (e.g., Spinal muscular atrophy)
  • Rickets (due to vitamin D deficiency)
  • Scoliosis-associated chest wall deformities

Memory Image
Shapes of the Anterior Chest Wall in
Health and Disease
The Pigeon and the Human

Artistic rendering of the different shapes of the anterior chest wall, comparing pectus carinatum, normal chest shape, and pectus excavatum in both humans and a pigeon.
The top image illustrates pectus carinatum (Latin: “carinatum” = “keel-shaped”, resembling the keel of a ship). This is the normal shape of the chest for the pigeon, but in humans, it may indicate hyperinflation seen in emphysema or asthma. Additionally, in congenital heart disease (CHD) with right ventricular (RV) enlargement (e.g., Tetralogy of Fallot, pulmonary hypertension, Ebstein anomaly), chronic pressure overload can cause the sternum to protrude forward.
The middle image represents a normal human chest shape, but the pigeon depicted has an abnormally flattened chest, deviating from its natural keel-shaped anatomy.
The bottom image demonstrates pectus excavatum, which is abnormal in both humans and the pigeon, characterized by an inward depression of the sternum.

Ashley Davidoff, MD
TheCommonVein.com
(lungs-0799)

Basic Science

1. What is the primary anatomical abnormality in pectus excavatum?

A) Lateral displacement of the clavicles
B) Posterior displacement of the sternum
C) Rotation of the vertebral column
D) Outward bowing of the ribs

Correct Answer: B — Posterior displacement of the sternum

• Pectus excavatum is defined by inward (posterior) depression of the sternum into the thoracic cavity.

Why the others are incorrect:

• A) Clavicular displacement is not a typical feature.

• C) Vertebral rotation may occur in scoliosis, not pectus.

• D) Outward rib bowing is more typical of pectus carinatum, the opposite deformity.

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2. Which condition is most commonly associated with pectus excavatum?

A) Sarcoidosis
B) Marfan syndrome
C) Rheumatoid arthritis
D) Cystic fibrosis

Correct Answer: B — Marfan syndrome

• Connective tissue disorders like Marfan syndrome are strongly associated with chest wall deformities such as pectus excavatum.

Why the others are incorrect:

• A) Sarcoidosis affects the lungs and lymph nodes but is not linked to chest wall deformities.

• C) Rheumatoid arthritis primarily affects joints, not chest structure.

• D) Cystic fibrosis may lead to chest changes over time but does not cause congenital deformities like pectus.

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🩺 Clinical

3. Which symptom may be seen in moderate to severe pectus excavatum?

A) Productive cough with fever
B) Palpitations and exercise intolerance
C) Night sweats and hemoptysis
D) Severe right lower quadrant pain

Correct Answer: B — Palpitations and exercise intolerance

• Compression of the heart and lungs can lead to symptoms of restricted cardiac output and reduced respiratory reserve.

Why the others are incorrect:

• A) Suggests infection, not structural deformity.

• C) More typical of TB or cancer.

• D) Localizes to abdominal pathology, not chest wall.

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4. Why is the right heart border often obscured on CXR in pectus excavatum?

A) Heart failure with right atrial enlargement
B) Right middle lobe collapse
C) Lung compressed between the sternum and heart
D) Pleural effusion

Correct Answer: C — Lung compressed between the sternum and heart

• The depressed sternum compresses the adjacent lung tissue, increasing its density and obscuring the right heart border.

Why the others are incorrect:

• A) While right atrial enlargement can shift structures, it doesn’t explain the density over the border.

• B) Right middle lobe collapse also causes obscuration but would not account for the chest wall deformity.

• D) Effusions generally track inferiorly and laterally, not anteriorly.

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🩻 Radiology

5. What classic radiographic feature is seen on the lateral chest X-ray in pectus excavatum?

A) Forward angulation of the spine
B) Posterior depression of the sternum
C) Diaphragmatic elevation
D) Rib notching

Correct Answer: B — Posterior depression of the sternum

• Best appreciated on lateral view, this posterior angulation of the sternum is diagnostic of pectus excavatum.

Why the others are incorrect:

• A) Spinal curvature is related to scoliosis, not pectus.

• C) Diaphragmatic elevation occurs in other thoracic disorders.

• D) Rib notching is associated with aortic coarctation, not chest wall deformity.

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6. What explains the mediastinal shift to the left seen on frontal chest X-ray in pectus excavatum?

A) Right lung collapse
B) Right pleural effusion
C) Displacement of the heart by sternal depression
D) Tension pneumothorax

Correct Answer: C — Displacement of the heart by sternal depression

• The sternum pushes the heart into the left hemithorax, creating a shift of the cardiomediastinal silhouette.

Why the others are incorrect:

• A) Right lung collapse shifts the mediastinum toward the side of collapse, but would show different density patterns.

• B) Effusion would push the mediastinum away, but also cause blunting of the costophrenic angle.

• D) Pneumothorax would present with hyperlucency and absent lung markings — not described here.