What are the surface landmarks for locating the lungs and their fissures on the chest wall?

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Surface Anatomy of the Lungs: A Practical Guide

The lung surface markings can be reliably identified using specific rib and vertebral landmarks, with the oblique fissures running from T3/T4 posteriorly to the 6th rib laterally, and the horizontal fissure at the 4th rib anteriorly on the right side.

Lung Borders and Apices

Upper Borders (Apices)

  • Apex of both lungs: Extends 2-3 cm above the medial third of the clavicle
  • Posteriorly reaches the level of C7 vertebra

Anterior Borders

  • Right lung: Descends from sternoclavicular joint → follows sternal edge → reaches 6th costal cartilage
  • Left lung: Similar path but deviates laterally at 4th costal cartilage (cardiac notch) → returns medially at 6th costal cartilage

Lower Borders (Diaphragmatic Surface)

The inferior lung margins follow these landmarks 1:

  • Midclavicular line: 6th rib
  • Midaxillary line: 8th rib
  • Posteriorly (scapular line): 10th rib
  • Paravertebral: T10 vertebra

Clinical Pearl: The pleural reflection extends approximately 2 ribs lower than the lung border, creating the costophrenic recess.

Interlobar Fissures

Oblique Fissures (Both Sides)

Based on high-resolution CT data from 250 patients 1:

Left oblique fissure (most common positions):

  • Posteriorly: 4th rib at the medial border of scapula (45% of cases)
  • Laterally (midaxillary line): 6th rib (52% of cases)
  • Anteriorly: Reaches 6th rib at midclavicular line, terminating in anterior third of hemidiaphragm (60% of cases)

Right oblique fissure (most common positions):

  • Posteriorly: 5th rib at medial scapular border (50% of cases)
  • Laterally: 6th rib (50% of cases)
  • Anteriorly: Anterior third of hemidiaphragm (71% of cases)

Memory aid: The oblique fissure follows a line from T3 spinous process (when arm is raised overhead) → wraps around chest wall → ends at 6th rib/costochondral junction anteriorly.

Horizontal Fissure (Right Lung Only)

1 demonstrates:

  • Origin: Intersects the oblique fissure at its middle third (61% of cases)
  • Anterior termination: 4th rib or 4th costal cartilage at sternal border (51% of cases)
  • Runs horizontally from midaxillary line at 5th rib → 4th rib anteriorly

Important Clinical Considerations

Individual Variation

Significant anatomical variability exists 1. The fissure positions vary considerably between individuals:

  • Left oblique fissure: Most commonly linear (78%)
  • Right oblique fissure: S-shaped or linear configurations (28% each)
  • Fissure positions remain stable between inspiration and expiration in 90% of cases

Practical Application

When performing procedures (thoracentesis, chest tube placement, physical examination):

  • Safe zone for thoracentesis: Above the 9th rib posteriorly to avoid subdiaphragmatic organs
  • Chest tube placement: Typically 4th-5th intercostal space, midaxillary line (triangle of safety)
  • The diaphragm can rise to the 5th intercostal space on expiration

Pediatric Differences

In children 2, key variations include:

  • Cardiac apex at 5th intercostal space (birth to age 4), then 4th intercostal space (ages 4-12)
  • Diaphragm domes are flatter and only one rib level higher than anterior border
  • Lower diaphragm border at 6th-7th rib (midclavicular), 8th rib (midaxillary), T11 posteriorly

Clinical Pitfall to Avoid

The most common error is underestimating how high the diaphragm rises during expiration and how much abdominal contents extend into the thoracic cavity. Always count ribs carefully and enter above the rib (not below) to avoid neurovascular bundles that run along the inferior rib margin.

References

2
Research

A reappraisal of pediatric thoracic surface anatomy.

Clinical anatomy (New York, N.Y.), 2017

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