The tracheobronchial tree typically divides into eparterial and hyparterial bronchi in the right lung, while the left lung has one principal bronchus.

Anatomical variations in the bronchial tree are frequently observed during routine cadaveric dissections, with some studies finding that a majority of individuals may have at least one variation. These variations, which differ from the standard anatomical pattern, are important for clinicians, radiologists, and surgeons to be aware of for accurate diagnosis and safe intervention. The tracheobronchial tree demonstrates a highly ordered branching pattern that forms the anatomical basis for segmental lung organization and surgical resection. Classical studies by Brock and Boyden established the concept of bronchopulmonary segments and highlighted the close relationship between bronchial and vascular structures [1, 2].

Despite this structured arrangement, anatomical variations in bronchial branching are frequently encountered. Modern radiological evaluations using multidetector computed tomography (CT) have shown that variations such as tracheal bronchi, accessory segmental bronchi, and atypical lobar branching patterns are not uncommon and are clinically significant [3, 4].

Pulmonary venous anatomy also exhibits considerable variability. Although typically two pulmonary veins from each lung drain into the left atrium, studies have reported accessory veins, common trunks, and anomalous drainage patterns that may complicate thoracic surgical and interventional procedures [5, 6]. Similarly, fissural variations, including incomplete or absent fissures, have been documented in both cadaveric and imaging studies, with implications for radiological interpretation and lobar resections [7, 8]. These variations originate from disturbances in branching morphogenesis and mesenchymal remodeling during embryonic lung development.

Therefore, detailed anatomical documentation through cadaveric studies remains essential for enhancing clinical preparedness and minimizing procedural complications. Anatomical variations in bronchial branching may influence surgical approaches, lung resections, bronchoscopy, and interpretation of imaging studies. This article reports a bronchial variation identified during routine dissection of MBBS students’ cadavers.

MATERIALS AND METHODS

During routine dissection of the thoracic cavity for undergraduate teaching, the lungs were removed following standard anatomical procedures. A few old specimens (total 68) from the Department of Anatomy, G. S. Medical College & Hospital, were procured for the study.

Cadaveric dissection remains a cornerstone of anatomical education and continues to provide invaluable insights into rare anatomical variations.

Cadavers Details

• Sex: Adult Males and Females
• Age:50-65yr
• Preservation: Formalin-embalmed cadaver
• Institution: GS MEDICAL COLLEGE &HOSPITAL, HAPUR.

Observation

During routine dissection of the thoracic cavity for undergraduate teaching, the lungs were removed following standard anatomical procedures. On careful examination of the bronchial tree, an anatomical variation in the bronchial branching pattern was observed.

Description of Variation

The right main bronchus showed an additional bronchial branch arising directly from it, supplying part of the upper lobe (tracheal or eparterial bronchus) in11 lungs.

Fig.–1Hilum Structures of Right Lung showing variation in Superior and Inferior Pulmonary veins and three bronchi

Fig.–2 Hilum Structures of Right Lung showing variation in Superior and Inferior Pulmonary veins

The left lung demonstrated an accessory lobar bronchus, resulting in an atypical segmentation in 13 lungs.

Fig.–3 Hilum Structures of Left Lung showing variation in Superior Pulmonary veins and two bronchi

Fig.–4 Hilum Structures of Left Lung showing variation in Superior and Inferior Pulmonary veins and two bronchi

The two right and two left lungs also have variation in superior or inferior pulmonary vein branches and two lungs without fissures.

Fig. --5 Hilum Structures of Left Lung showing variation in Superior and Inferior Pulmonary veins and two bronchi.

Fig. –6 Right Lung showing no fissure

This variation deviated from the classical anatomical description found in standard textbooks. The remaining bronchial branches and lung parenchyma appeared normal.

DISCUSSION

Bronchial variations occur due to altered branching patterns during embryological development of the respiratory diverticulum from the foregut. Abnormal persistence or regression of bronchial bud scan result in accessory bronchi or altered lobar distribution.

Reported bronchial variations include:

• Tracheal bronchus.
• Accessory lobar bronchi.
• Absence or fusion of segmental bronchi.

Such variations are clinically significant because:

• They may cause misinterpretation on CT scans or bronchoscopy.
• They increase the risk of incomplete lung resection during surgery.
• They can complicate endotracheal intubation and anesthesia.

.Table1. Comparison Table of Bronchial and Pulmonary vessels with fissure variation with Previous Studies

Anatomical variations in the tracheobronchial tree are well documented in the literature and have substantial clinical implications in radiological interpretation, bronchoscopy, thoracic surgery, and anaesthetic practice. Anatomical variations of the tracheobronchial tree have been recognized since the classical works of Brock R. C. [1], which provided one of the earliest comprehensive descriptions of bronchial branching patterns. This was further elaborated by Boyden E. A. [2], who detailed the segmental anatomy of the lungs and emphasized the developmental basis of bronchopulmonary segmentation.

Subsequent radiological reassessment by Ghaye B. et al. [3] revisited congenital bronchial abnormalities using imaging correlation, highlighting their clinical importance. Early morphologic analysis by Foster-Carter A. F. [4] described bronchopulmonary abnormalities and accessory bronchi, reinforcing the concept that variations are not uncommon. Radiologic evaluation of pulmonary venous drainage by Marom E. M. et al. [5] demonstrated that venous variations may significantly influence interventional cardiology and thoracic procedures. Similarly, fissural morphology was examined in cadaveric detail by Meenakshi S. et al. [6], who reported frequent incomplete and absent fissures resulting from developmental factors.

More recent cadaveric research by Regina C. et al. [7] documented variations in lung fissures and pulmonary venous drainage, reporting a high frequency of venous pattern variability. Advanced three-dimensional CT reconstruction studies by Zhao B. et al. [8] further refined understanding of bronchial anatomy, particularly in relation to the middle lobe. Expanded radiologic evaluation of pulmonary venous variations by Marom T. et al. [9] reinforced the importance of pre-procedural vascular mapping. CT-based observational work by Singh S. et al. [10] demonstrated that fissural variations are frequently encountered in clinical imaging, often influencing radiologic interpretation.

Comprehensive anatomical documentation of human structural variations by Bergman R. A. et al. [11] provided an extensive reference framework for understanding bronchovascular deviations. Cadaveric studies across various populations have consistently reported morphological variability. George B. M. et al. [12] observed notable fissural and lobar variations in Indian cadavers. Ajeevan G. et al. [13] reported similar findings in Nepalese specimens. Kumari M. T. et al. [14] documented fissural and lobar anomalies in a South Indian population.

A detailed review of pulmonary vascular anatomy by Asha K. et al. [15] emphasized the surgical importance of recognizing vascular variants. Three-dimensional CT-based vascular and bronchial mapping by Deng Y. et al. [16] further illustrated the precision achievable in preoperative planning. Bronchoscopic anatomic correlation by Silvia M. R. et al. [17] highlighted segmentation variability relevant to endobronchial procedures.

Rare bronchial segmentation patterns were described in a case report by Sharma P. et al. [18], demonstrating unusual right upper lobe bronchial division. Similarly, Zhu S. et al. [19] analyzed branching patterns of bronchi and associated vessels in the superior segment of the right lower lobe using CT bronchography and angiography. Variations in lobar bronchi and bronchopulmonary segments were also documented by Sathidevi V. K. [20].

Further cadaveric hilar studies by Jethva N. K. et al. [21] and Neil J. et al. [22] reported considerable diversity in hilar arrangement and lobar anatomy. A South African morphological investigation by Refilwe S. et al. [23] reinforced the influence of demographic and population factors on bronchovascular patterns.

A cadaveric analysis published in the Bratislava Medical Journal further described accessory fissures and variations in fissural completeness. A recent bronchoscopic and cadaveric investigation reported bronchial segmentation variations in approximately 61.9% of lungs, indicating that airway branching diversity may be more frequent than traditionally assumed. Finally, a surgical-oriented cadaveric overview by Arthi G. et al. [24] documented multiple bronchi at the hilum and highlighted the implications for thoracic surgery.

In comparison with these studies, the present investigation observed bronchial variations in 35.3% of lungs, including tracheal/eparterial bronchi (16.2%) and accessory lobar bronchi (19.1%). Pulmonary venous drainage variations were noted in 5.9%, and fissural absence in 2.9% of specimens. These findings fall within the spectrum reported in both classical anatomical literature and contemporary cadaveric and radiologic studies.

The embryological basis of these variations stems from abnormalities in lung bud formation and bronchial branching morphogenesis during early intrauterine development. Disturbances in programmed branching, mesenchymal apoptosis, and vascular differentiation can lead to accessory bronchi, anomalous veins, and atypical fissures.

Awareness of such developmental mechanisms assists clinicians in anticipating associated anatomical deviations.

These collective findings underscore the importance of thorough anatomical knowledge for clinicians. Radiologists must recognize variant bronchial and fissural anatomy to prevent misdiagnosis on imaging studies. Pulmonologists and bronchoscopists should be alert to bronchial segmentation variants that might complicate airway navigation or sampling. Thoracic surgeons require precise anatomic detail for surgical planning, especially in segmental resections and minimally invasive procedures. Preoperative high- resolution imaging with three-dimensional reconstruction plays an increasingly crucial role in identifying these variants and guiding safe clinical decision-making. Cadaveric findings such as this contribute valuable data to anatomical literature and help improve awareness among clinicians and surgeons.

CONCLUSION

The present cadaveric study demonstrates a significant prevalence of variations in the bronchial tree, pulmonary venous drainage, and fissural morphology. Bronchial variations were the most frequently observed, followed by venous and fissural anomalies. These findings are consistent with both foundational anatomical literature and recent imaging and dissection-based research.

Recognition of such anatomical variants is essential for accurate radiological assessment, safe bronchoscopic procedures, effective anesthetic management, and careful surgical planning. A combination of thorough anatomical understanding and detailed preoperative imaging can reduce the risk of diagnostic errors and procedural complications. These insights support continued emphasis on detailed anatomical training and routine evaluation of broncho vascular and fissural variants in clinical practice. Cadaver-based studies continue to play a vital role in identifying and documenting these variations for educational and clinical purposes.

Clinical Significance

• Important for thoracic surgeries and lung resections.
• Helps avoid diagnostic errors in radiology.
• Essential for safe bronchoscopy and airway management.

Acknowledgements

The authors acknowledge the body donor for contributing to medical education and express gratitude to the Department of Anatomy, G S Medical College, Hapur for support during the study.

REFERENCES

1. Brock, R. C. The Anatomy of the Bronchial Tree. Oxford University Press, 1946, pp. 72–74.
2. Boyden, E. A. “Segmental Anatomy of the Lungs: A Study of the Patterns of the Segmental Bronchi and Related Pulmonary Vessels.” Journal of Anatomy, vol. 90, pt. 1, Jan. 1956, pp. 158–159.
3. Ghaye B, Szapiro D, Fanchamps J M et al. “Congenital Bronchial Abnormalities Revisited.” Radiographics, vol. 21, no. 1, 2001, pp. 105–119.
4. Carter, A. F. “Broncho-Pulmonary Abnormalities.” British Journal of Tuberculosis and Diseases of the Chest, vol. 40, 1946, pp. 111–124.
5. Marom, E. M, Herndon J E, Kim Y H et al. “Variations in Pulmonary Venous Drainage to the Left Atrium: Implications for Radiofrequency Ablation.” Radiology, vol. 230, no. 3, 2004, pp. 824–829.
6. S Meenakshi., K. Y. Manjunath, and V. Balasubramanyam. “Morphological Variations of Lung Fissures and Lobes.” Indian Journal of Chest Diseases and Allied Sciences, vol. 46, no. 3, 2004, pp. 179–182.
7. Regina, C., J. Kalaivannan, and K. Santhini Arul Selvi. “A Cadaveric Study of Variations in Lung Fissures and Drainage Patterns of Pulmonary Veins at the Hilum with Its Clinical Implications.” Cureus, vol. 16, no. 10, 2024, e71909.
8. Zhao B., W. Wu, and G. Duan “Observation of Bronchial Anatomy and Variation of the Middle Lobe of the Right Lung Based on Three-Dimensional Reconstruction of Lung CT.” Journal of Cardiothoracic Surgery, vol. 20, no. 1, 2025, p. 172.
9. Marom T J, et al. “Advanced Imaging of Pulmonary Venous Variations and Clinical Relevance.” American Journal of Roentgenology, vol. 213, no. 1, 2019, pp. W10–W18.
10. Singh S and Singh R. “Anatomical Variations in Fissures of Lung on CT Scan: Observational Study.” Indian Journal of Radiology and Imaging, vol. 31, no. 4, 2022, pp. 797–804.
11. Bergman, Ronald A., et al. Compendium of Human Anatomic Variation: Text, Atlas, and World Literature. Urban & Schwarzenberg, 1988, pp. 580–593.
12. George B M, Nayak S B., and Marpalli S. “Morphological Variations of the Lungs: A Study Conducted on Indian Cadavers.” Anatomy & Cell Biology, vol. 47, 2014, pp. 253–258.
13. Gautam A, Chaulagain R., and Dhungel D. “Morphological Variations of the Lungs: A Cadaveric Study.” Nepal Medical College Journal, vol. 23, no. 4, Dec. 2021, pp. 315–318.
14. Kumari, M. T, Rajasree G etal. “Variations in Lung Fissures and Lobes Morphology in Population of Andhra Pradesh of South India (A Cadaveric Study).” Siberian Scientific Medical Journal, vol. 42, no. 4, 2022, pp. 74–78.
15. Kandathil A and Chamarthy M. “Pulmonary Vascular Anatomy and Anatomical Variants.” Cardiovascular Diagnosis and Therapy, vol. 8, no. 3, 2018, pp. 201–220.
16. Deng Y, Cai S, Huang C et al. “Anatomical Variation Analysis of Left Upper Pulmonary Blood Vessels and Bronchi Based on Three-Dimensional Reconstruction of Chest CT.” Frontiers in Oncology, vol. 12, 2022, 1028467.
17. Silvia, M. R., et al. “The Bronchial Segmentation and Its Anatomical Variations: A Clinical-Anatomic and Bronchoscopy Study.” Annals of Anatomy, vol. 235, 2021, article 151677.
18. Sharma P, Rai D K,Kumar M et al. “Five Segments of the Right Upper Lobe Bronchus on Bronchoscopic Anatomy: A Rare Case Report and Review of Literature.” EMJ Respiratory, vol. 11, no. 1, 2023, pp. 115–119.
19. Zhu, Shusheng, et al. “Branching Patterns and Variations of the Bronchus and Blood Vessels in the Superior Segment of the Right Lower Lobe: A Three-Dimensional Computed Tomographic Bronchography and Angiography Study.” Journal of Thoracic Disease, vol. 15, no. 12, 2023, pp. 6879–6888.
20. K .Sathidevi. “Anatomical Arrangement of the Lobar Bronchi, Bronchopulmonary Segments and Their Variations.” International Journal of Research in Medical Sciences, vol. 4, no. 11, Nov. 2016, pp. 4928–4932.
21. Jethva N K. and Chavda H S. “A Cadaveric Study on Morphological Variations of Lobar and Hilar Anatomy of Human Lungs.” International Journal of Anatomy and Research, vol. 7, no. 1.2, 2019, pp. 6250–6253.
22. Neil, J., et al. “Morphological Study of Lobes, Fissures and Pulmonary Hilar Structures.” International Journal of Anatomy and Research, vol. 7, no. 1.3, 2019, pp. 6298–6301.
23. Refilwe, S., Megan P., and Kentse S. M. “Morphological Variations of Fissures, Lobes, and Hilar Pattern of the Lung in a Select South African Sample.” Surgical and Radiologic Anatomy, vol. 46, 2024, pp. 2005–2017.
24. Ganapathy A., Tandon R, Kaler S et al. “Cadaveric Study of Lung Anatomy: A Surgical Overview.” Journal of Medical Research and Innovation, vol. 3, no. 1, 2018, pp. 1–4.
25. Soni V K., Yadav S, Arora L et al. “Morphological Anatomy of Accessory Fissures in Human Cadaveric Lungs.” International Journal of Environmental Sciences, vol. 11, no. 13, 2025, pp. 1648–1653.
26. Vidulatha K and Sundar G. “Incomplete and Accessory Pulmonary Fissures: Gross Anatomical Variations and Their Clinical Implications.” International Journal of Medical and Pharmaceutical Research, vol. 6, no. 6, 2025, pp. 1669–1676.