Inferior Phrenic Artery Variations and a Novel Classification of Aortic and Non-aortic Origins: An Observational CT Angiographic Study

Background and aim The inferior phrenic arteries (IPAs) usually originate from the abdominal aorta as collateral branches and are small arteries that supply the diaphragm. Related pathologies include hemoptysis, bleeding during surgery or trauma, Mallory-Weiss tear, gastroesophageal cancer, and collateral blood supply to hepatocellular carcinoma. Knowledge about variations involving these arteries is important for clinicians, radiologists, and surgeons. This study aims to observe variations in the origin of IPAs and propose a novel classification of aortic and non-aortic origin arteries based on CT angiographic findings. Materials and methods The study was conducted in the Department of Anatomy in collaboration with the Department of Radiodiagnosis. Computerized tomographic angiograms of 100 subjects aged 15-70 years were retrospectively collected and reviewed after applying inclusion and exclusion criteria. The site and pattern of origin of the IPAs were observed on reconstructed CT images. The arteries were grouped according to the type of variation observed, and the prevalence of specific variations was estimated and compared on the basis of gender. A novel classification of arterial variants was also proposed. Results IPA anatomy was studied in 100 subjects. Instead of the expected 200 IPAs, 203 arteries were observed due to the presence of three accessory arteries. Out of these 203 arteries, 131 (64.53%) were of aortic origin - 113 (86.26%) with normal origin and 18 (13.74%) with variant (displaced) origin. The remaining 72 arteries (35.47%) were of non-aortic origin (misplaced arteries). Thus, two types of arterial variations were identified: displaced arteries (variant aortic origin) and misplaced arteries (non-aortic origin). Conclusions The total prevalence of variations in IPAs was found to be 44.34%. Precise knowledge of these variations is crucial for medical management and before surgical or interventional treatments. The study uniquely reports the displaced variants of IPAs and proposes a classification into different types based on the pattern of origin.