Anatomical Variations of the Lung Lobes and Fissures: A Systematic Review and Meta-Analysis

The lungs' fissural and lobar variations are clinically and anatomically important, with direct implications for anatomists, radiologists, and thoracic surgeons. Although standard anatomical textbooks commonly describe fissures as complete, numerous studies have reported substantial variability, including incomplete, absent, and accessory fissures. These variations may complicate surgical procedures, affect disease spread, and lead to misinterpretation of imaging findings. Therefore, quantifying the prevalence of fissural and lobar variations is essential for accurate clinical planning, reliable radiologic interpretation, and effective anatomical education. A systematic search was conducted across PubMed, Hinari, Crossref, and Google Scholar, as well as relevant anatomical journals, in accordance with Evidence-Based Anatomy Workgroup recommendations and reported following PRISMA 2020 guidelines. Eligible anatomical studies were included, and study quality was assessed using a standardized appraisal tool. Meta-analysis was performed using MetaXL with a random-effects model to estimate the pooled prevalence and distribution of lung variations. Among all evaluated lungs, anatomical variations were observed in 42%, with 63% occurring on the right side. When assessed independently, variations were present in 55% of right lungs and 33% of left lungs. The right horizontal fissure was complete in 54%, incomplete in 35%, and absent in 11%, while the right oblique fissure was complete in 77%. The left oblique fissure was complete in 72%, incomplete in 26%, and absent in 2%. Accessory fissures were present in 14% of both right and left lungs, most commonly the inferior accessory fissure on the right (6%) and the left minor fissure on the left (8%). Lung fissural and lobar variations occur in nearly half of individuals, with distinct right- and left-sided patterns and variable completeness. Awareness of these variations is essential for accurate anatomical understanding, surgical planning, radiological interpretation, and minimizing complications in thoracic procedures.