Anatomic variations of cervical part of thoracic duct: a systematic review

The thoracic duct is the largest lymphatic channel of the human body, and presents with great anatomical variation at its cervical segment. Injury of the thoracic duct can result in local or systemic severe complications. In order to identify the prevalence of the anatomical variations of the terminal portion of the thoracic duct, this study was performed according to PRISMA guidelines. The l-square was used to assess heterogeneity. A wide search was conducted in PubMed/ Embase/ Medline until September 2019. Out of 28 potentially relevant studies identified by literature search, 14 studies comprising 751 patients were included in the final analysis. The prevalence of thoracic duct ending with a single terminal duct was found at 63% (37%-85%) of the patients. Left internal jugular vein, left subclavian vein, left jugulosubclavian angle, or another vein, was found to receive at least one terminal branch of the thoracic duct in 32% (18%-47%), 27% (13%43%), 32% (16%-51%) and 7% (0%-19%) of the cases, respectively. Each time the thoracic duct drained into the left internal jugular vein, the left subclavian vein and the left jugulosubclavian angle, a single terminal branch pattern was observed in 58% (21%-92%), 49% (6%- 93%) and 76% (49-96%) of the cases respectively. The thoracic duct emptied into the left internal jugular vein, the left subclavian vein and the left jugulosubclavian angle in the majority of cases. Patients with a terminal branch at the left jugulosubclavian angle showed higher prevalence of single terminal branch pattern, whereas patients with a terminal branch at the left internal jugular vein or the left subclavian vein presented with similar prevalence of single- and multiple-branch patterns. This information should prove useful in order to reduce iatrogenic thoracic duct lacerations.