Lymphatic drainage of the peritoneal space: A pattern dependent on bowel lymphatics

Background: Understanding lymph drainage patterns of the peritoneum could assist in staging and treatment of gastrointestinal and ovarian malignancies. Sentinel lymph nodes (SLNs) have been identified for solid organs and the pleural space. Our purpose was to determine whether the peritoneal space has a predictable lymph node drainage pattern. Methods: Rats received intraperitoneal injections of near-infrared (NIR) fluorescent tracers: namely, quantum dots (designed for retention in SLNs) or human serum albumin conjugated with IRDye800 (HSA800; designed for lymphatic flow beyond the SLN). A custom imaging system detected NIR fluorescence at 10 and 20 minutes and 1, 4, and 24 hours after injection. To determine the contribution of viscera to peritoneal lymphatic flow, additional cohorts received bowel resection before NIR tracer injection. Associations with appropriate controls were assessed with the chi(2) test. Results: Quantum dots drained to the celiac, superior mesenteric, and periportal lymph node groups. HSA800 drained to these same groups at early time points but continued flowing to the mediastinal lymph nodes via the thoracic duct. After bowel resection, both tracers were found in the thoracic, not abdominal, lymph node groups. Additionally, HSA800 was no longer found in the thoracic duct but in the anterior chest wall and diaphragmatic lymphatics. Conclusions: The peritoneal space drains to the celiac, superior mesenteric, and periportal lymph node groups first. Lymph continues via the thoracic duct to the mediastinal lymph nodes. Bowel lymphatics are a key determinant of peritoneal lymph flow, because bowel resection shifts lymph flow directly to the intrathoracic lymph nodes via chest wall lymphatics.