We present a rare case of a trilobed left lung, where the left lung possesses three distinct lobes separated by both

horizontal and oblique fissures, mirroring the typical structure of the right lung. This anatomical variation was

discovered during a routine cadaveric dissection at Nnamdi Azikiwe University. The study aims to document

and describe this variation, compare it with classical lung anatomy, explore potential embryological causes, and

Human anatomy has long been established as a foundational pillar of medical science, yet it is also a field

enriched by continual discoveries of anatomical variations. Traditionally, the human lungs are asymmetrical: the

right lung comprises three lobes (superior, middle, and inferior), separated by the horizontal and oblique fissures,

whereas the left lung typically has only two lobes (superior and inferior) separated by a single oblique fissure,

accommodating the space taken by the heart (Drake et al, 2020).

However, during a routine cadaveric dissection in a medical anatomy lab, a rare and unusual finding was

encountered: the left lung of the subject cadaver possessed three distinct lobes, clearly demarcated by both a

horizontal and an oblique fissure, mirroring the typical structure of the right lung. This anomaly challenges the

Failure to recognize such variants can lead to diagnostic errors, surgical complications, or misinterpretation in

imaging.

1. To document and describe an anatomical variation in the left lung having three lobes.

2. To compare the observed anatomical variant with classical lung anatomy.

3. To explore potential embryological causes for the lobation difference.

4. To highlight the clinical relevance of anatomical variations in pulmonary anatomy.

This study contributes to the growing body of literature on anatomical variability, particularly in thoracic

anatomy. It serves as a teaching tool for medical educators and students and provides a reference point for

The study is limited to a single cadaveric case observed in a dissection lab. While it may not provide a statistically

significant sample size, it raises important questions for future anatomical and embryological research.

A formalin-embalmed adult male cadaver was dissected at the Gross Laboratory Department of Anatomy,

Nnamdi Azikiwe University, following standard protocols (Carmine & Smith, 2019). The thoracic cavity was

opened, and the lobar and fissural anatomy of both lungs was examined. The anomalous left lung structure was

photographed and compared with standard anatomical references.

Materials Used

7. Notebook and pen for in-situ notes and diagrams

8. Anatomy textbooks and atlases for real-time comparison and referencing

The thoracic cavity was carefully opened, and observations were made regarding the number of lobes and

fissures in both lungs. The left lung was found to have three clearly demarcated lobes, separated by a horizontal

and an oblique fissure. Observations were compared with classical texts and documented photographically. The

bronchial tree of the left lung was examined to assess corresponding bronchial division.

During routine anatomical dissection of a male adult cadaver in the Gross Anatomy Laboratory at Nnamdi

Azikiwe University, an anatomical variation in the lobation of the left lung was observed.

External Features of the: The left lung exhibited three well-defined lobes, separated by two fissures:

 Located at the apex of the lung and anteriorly.

 Separated from the middle lobe by a clearly demarcated horizontal fissure.

 Situated between the superior and inferior lobes.

 Horizontal Fissure: Extended horizontally from the anterior border of the lung, creating a separation

between the superior and middle lobes.

 Oblique Fissure: Extended from the posterior surface obliquely downward and forward to separate the

middle from the inferior lobe.

The right lung of the same cadaver was also examined and found to have the normal three-lobed structure

separated by a horizontal and an oblique fissure.

High-resolution images were taken from multiple angles showing:

 The complete left lung with three distinct lobes.

This observation represents a rare anatomical variation not commonly documented in literature and raises

considerations for clinical imaging, thoracic surgery, and pulmonary diagnostics.

Fig. 2. The left lung presented with three lobes:

A horizontal fissure separating the superior and middle lobes.An oblique fissure separating the middle and

inferior lobes.

Fig 3: Anatomical illustration of a trilobed left lung,

Demonstrating a rare variation in lung morphology. This description provides a clear and concise overview of

the diagram, highlighting the key features of the trilobed left lung © Promise N. Opkechi

Fig.6: The right lung of the same cadaver with the normal three-lobed structure separated by a horizontal and an

oblique fissure.

Fig 7: Anatomical illustration of a trilobed left lung,Demonstrating a rare variation in lung morphology.

This description provides a clear and concise overview of the diagram,Highlighting the key features of the

trilobed left lung © Promise N. Opkechi

Fig. 8. The left lung presented with three lobes:

A horizontal fissure separating the superior and middle lobes.An oblique fissure separating the middle and