Novel Arrangement of the Thoracic Duct at the Diaphragm

Introduction and Objective: Thoracic duct variations have been reported in 40-60% of the population. The thoracic duct has been typically described as originating from the superior aspect of the cisterna chyli, passing through the aortic hiatus of the diaphragm to enter the posterior mediastinum, and traveling superiorly between the aorta and azygos vein. Research has indicated variations in the course of the thoracic duct in the thoracic cavity. However, the current finding has not been reported in the literature. The objective of this research was to describe the observed variation of the thoracic duct and determine its clinical implications. Materials and Methods: Routine and fine dissection techniques were used to reveal the pathway of the thoracic duct at the diaphragm in a 55-year-old female embalmed donor. Results: The thoracic duct was shown to pass lateral to the aortic hiatus and was positioned directly under the diaphragm muscle attachment at the lumbar spine. Conclusions: To the authors' knowledge, this is the first time this variation has been described. The current variation is distinct in its course traveling under the diaphragm rather than through the aortic hiatus. This novel arrangement may have clinical implications. Significance: The clinical significance of the current finding may include altering lymphatic flow and drainage, may present as a complication in thoracic surgical procedures, alter imaging results and diagnostic procedures, and may potentially contribute to chronic conditions. Disruption or obstruction to the flow of lymphatic drainage can lead to chylothorax. Physical therapy treatment should avoid increasing pressure on the thoracic duct or disrupting the lymphatic system's flow. Complications from the current condition may result from heavy weight lifting, deep breathing, or any activity that intensifies pressure on the diaphragm. The lymphatic build-up can cause other contraindications such as swelling, skin changes, reduced ROM and mobility, and increased pain and discomfort for patients. For medical professionals, understanding the anatomy of the thoracic duct and lymphatic system is essential to prevent complications.