Hoover’s sign refers to abnormal movements of the thoracic or abdominal structures during respiration or leg exertion:

• Inward movement of the costal margins with inspiration.

  • Bilateral: commonly seen in emphysema with acute respiratory distress.

  • Unilateral: occurs in intrathoracic disorders causing flattening of one-half of the diaphragm.

• Contralateral leg-lifting movement occurs when the patient is instructed to press a leg against the examination table; absent in hysteria or malingering, serving as a functional assessment.

Pathophysiology

• Pulmonary/diaphragmatic component:

  • In emphysema, hyperinflation and flattening of the diaphragm lead to paradoxical inward motion of the lower rib cage during inspiration.

  • Unilateral diaphragmatic paralysis or flattening causes inward motion only on the affected side.

• Functional/neurologic component:

  • Hoover originally described the contralateral leg movement as a test of effort.

  • In malingering or conversion disorders, the patient cannot generate the normal counter-pressure, and the expected leg movement is absent.

Examination Technique

1. Costal movement assessment:

   • Position the patient seated or supine.

   • Observe inward or outward motion of the lower costal margins during quiet and deep inspiration.

2. Functional leg assessment:

   • Patient lies supine.

   • Ask the patient to press one leg down against the examination table.

   • Observe the contralateral leg for an involuntary upward/lifting motion.

   • Absence of this movement may indicate functional weakness or non-organic disorder.

Clinical Features

Differential Diagnosis

Pediatric considerations

• Rarely assessed in neonates.

• Congenital diaphragmatic anomalies may mimic unilateral costal movement.

Geriatric considerations

• Chronic pulmonary disease may exaggerate Hoover’s sign.

• Useful in distinguishing effort-related functional weakness from true neuromuscular deficits.

Limitations

• Interpretation may be influenced by patient cooperation.

• Requires careful observation to differentiate between organic and functional causes.

• Best used in combination with imaging (CXR, ultrasound) or pulmonary function testing for diaphragmatic disorders.

Patient counseling

• Explain that Hoover’s sign helps evaluate diaphragmatic function and effort generation.

• Reassure patients regarding the non-invasive nature of the test.

• In functional disorders, emphasize that absence of the expected movement does not indicate intentional deception but may reflect unconscious conversion.

Conclusion

Hoover’s sign is a valuable bedside tool for assessing diaphragmatic function, pulmonary pathology, and functional effort. Recognition of paradoxical rib movements or absent contralateral leg lift can aid in distinguishing organic respiratory disease from functional or non-organic disorders, guiding further evaluation and management.

References

1. Jetté J, et al. Clinical Examination of the Respiratory System. Chest. 2014;146(6):1687–1695.

2. Brutsche MH, et al. Hoover sign in severe emphysema: Clinical and functional significance. Respiration. 2000;67:552–557.

3. McPhee SJ, Papadakis MA. Current Medical Diagnosis & Treatment. 60th ed. New York: McGraw-Hill; 2021.

4. American Thoracic Society. Diaphragm and Respiratory Muscle Function. ATS Guidelines. 2017.