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.

Sentinel lymph node mapping of the gastrointestinal tract by using invisible light.

BACKGROUND: Because many gastrointestinal (GI) tumors spread by way of lymphatics, histological assessment of the first draining lymph nodes has both prognostic and therapeutic significance. However, sentinel lymph node mapping of the GI tract by using available techniques is limited by unpredictable drainage patterns, high background signal, and the inability to image lymphatic tracers relative to surgical anatomy in real time. Our goal was to develop a method for patient-specific intraoperative sentinel lymph node mapping of the GI tract by using invisible near-infrared light. METHODS: We developed an intraoperative near-infrared fluorescence imaging system that simultaneously displays surgical anatomy and otherwise invisible near-infrared fluorescence images of the surgical field. Near-infrared fluorescent quantum dots were injected intraparenchymally into the stomach, small bowel, and colon, and draining lymphatic channels and sentinel lymph nodes were visualized. Dissection was performed under real-time image guidance. RESULTS: In 10 adult pigs, we demonstrated that 200 pmol of quantum dots quickly and accurately map lymphatic drainage and sentinel lymph nodes. Injection into the mid jejunum and colon results in fluorescence of a single lymph node at the root of the bowel mesentery. Injection into the stomach resulted in identification of a retrogastric node. Histological analysis in all cases confirmed the presence of nodal tissue. CONCLUSIONS: We report the use of invisible near-infrared light for intraoperative sentinel lymph node mapping of the GI tract. This technology overcomes the limitations of currently available methods, permits patient-specific imaging of lymphatic flow and sentinel nodes, and provides highly sensitive, real-time image-guided dissection.

Sentinel lymph node mapping of the pleural space.

STUDY OBJECTIVES: Although the sentinel lymph node (SLN) concept has traditionally been applied to solid organs, we hypothesized that the pleural space might drain into a specific SLN group. The identification of such a nodal group could assist in the staging and treatment of pleural-based diseases, such as mesothelioma, or other lung cancers with visceral pleural invasion. The purpose of this study was to determine whether the pleural space has an SLN group. DESIGN: Sixteen rats underwent right or left pleural space injection of a novel lymph tracer, quantum dots (QDs), which have a hydrodynamic diameter of 15 nm and fluoresce in the near-infrared (NIR) spectrum. Nodal uptake of the entire thorax was imaged with a custom system that simultaneously acquired color video, NIR fluorescence of the QDs, and a merged picture of the two in real-time. Six pigs underwent right or left pleural space injection of QDs and similar imaging. MEASUREMENTS AND RESULTS: In the rat, the QDs drained solely to the highest superior mediastinal lymph node group, corresponding to lymph node station 1, according the regional lymph node classification for lung of the American Joint Committee on Cancer. In one rat, the injection of QDs in the left pleural space resulted in migration to the contralateral station 1 lymph node group. The injection of QDs in the right or left pleural space of the pig resulted in migration solely to the ipsilateral highest superior mediastinal lymph node group. CONCLUSIONS: NIR fluorescence imaging in two species demonstrated that the highest superior mediastinal lymph nodes of station 1 are the SLNs of the pleural space. This study also provides intraoperative feasibility and proof of the concept for identifying lymph nodes communicating with the pleural space on a patient-specific basis, in real-time, and with high sensitivity.

Intraoperative identification of esophageal sentinel lymph nodes with near-infrared fluorescence imaging.

OBJECTIVE: In esophageal cancer, selective removal of involved lymph nodes could improve survival and limit complications from extended lymphadenectomy. Mapping with vital blue dyes or technetium Tc-99m often fails to identify intrathoracic sentinel lymph nodes. Our purpose was to develop an intraoperative method for identifying sentinel lymph nodes of the esophagus with high-sensitivity near-infrared fluorescence imaging. METHODS: Six Yorkshire pigs underwent thoracotomy and received submucosal, esophageal injection of quantum dots, a novel near-infrared fluorescent lymph tracer designed for retention in sentinel lymph nodes. Six additional pigs underwent thoracotomy and received submucosal esophageal injection of CW800 conjugated to human serum albumin, another novel lymph tracer designed for uptake into distant lymph nodes. Finally, 6 pigs received submucosal injection of the fluorophore-conjugated albumin with an endoscopic needle through an esophagascope. These lymph tracers fluoresce in the near-infrared, permitting visualization of migration to sentinel lymph nodes with a custom intraoperative imaging system. RESULTS: Injection of the near-infrared fluorescent lymph tracers into the esophagus revealed communicating lymph nodes within 5 minutes of injection. In all 6 pigs that received quantum dot injection, only a single sentinel lymph node was identified. Among pigs that received fluorophore-conjugated albumin injection, in 5 of 12 a single sentinel lymph node was revealed, but in 7 of 12 two sentinel lymph nodes were identified. There was no dominant pattern in the appearance of the sentinel lymph nodes either cranial or caudal to the injection site. CONCLUSION: Near-infrared fluorescence imaging of sentinel lymph nodes is a novel and reliable intraoperative technique with the power to assist with identification and resection of esophageal sentinel lymph nodes.

Intraoperative sentinel lymph node mapping of the lung using near-infrared fluorescent quantum dots.

BACKGROUND: The presence of lymph node metastases is an important prognostic marker with regard to non-small-cell lung cancer (NSCLC). Assessment of the sentinel lymph node (SLN) for the presence of tumor may improve staging. Our objective was to develop an optical noninvasive imaging tool that would permit intraoperative SLN mapping and provide real-time visual feedback for image-guided localization and resection. METHODS: Invisible near-infrared (NIR) light penetrates relatively deeply into tissue and background autofluorescence is low. We have developed a NIR fluorescence imaging system that simultaneously displays color video and NIR images of the surgical field. We recently engineered 15 nm nonradioactive NIR fluorescent quantum dots (QDs) as optimal lymphotrophic optical probes. The introduction of these QDs into lung tissue allows real-time visualization of draining lymphatic channels and nodes. RESULTS: In 12 Yorkshire pigs (mean weight 35 kg) we demonstrated that 200 pmol of NIR QDs injected into lobar parenchyma accurately maps lymphatic drainage and the SLN. All SLNs were strongly fluorescent and easily visualized within 5 minutes of injection. In 14 separate injections QDs localized to a mediastinal node, whereas in 2 injections QDs localized to a hilar intraparenchymal node. Histologic analysis in all cases confirmed the presence of nodal tissue. CONCLUSIONS: We report a highly sensitive rapid technique for SLN mapping of the lung. This technique permits precise real-time imaging and therefore overcomes many limitations of currently available techniques.

In vivo optical imaging of pleural space drainage to lymph nodes of prognostic significance.

BACKGROUND: Understanding the spatial and temporal drainage patterns of the pleural space could have profound impact on the treatment of lung cancer and mesothelioma. The purpose of this study was to identify the in vivo pattern of drainage from the pleural space to prognostic lymph node stations. METHODS: Fifty-six rats underwent pleural space injection of a novel lymph tracer composed of recombinant human serum albumin (HSA) covalently conjugated to the near-infrared (NIR) fluorophore IRDye78 via an amide bond (HSA-78). Nodal uptake was imaged at 10, 20, 30, and 60 minutes and 4, 12, and 24 hours after injection with a custom system that simultaneously acquires color video, NIR fluorescence of HSA-78, and a merged picture of the two. Six pigs underwent the same procedure with imaging at 30 minutes, 1 hour, and 24 hours. RESULTS: In both the rat model and the pig model, HSA-78 drained from the pleural space to superior mediastinal lymph nodes first, followed by other intrathoracic and then extrathoracic lymph nodes over the course of 24 hours. CONCLUSION: NIR fluorescence imaging in two species shows that the superior mediastinal lymph nodes are the first to drain the pleural space. Over the course of 24 hours, the pleural space also communicates with other intrathoracic and then extrathoracic lymph nodes. This study also demonstrates an intraoperative method for identifying nodes communicating with the pleural space, with potential utility in the staging and/or resection of lung cancer and mesothelioma.