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

Abstract

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.

Figure 1. Imaging and Quantification of Peritoneal Lymph Flow Using Large Hydrodynamic Diameter QDs

A) The top row shows an in vivo, in situ superior mesenteric lymph node with QD uptake (arrow). The bottom row shows this QD-positive lymph node and adjacent QD-negative lymph after resection. Shown are the color video (left column), NIR fluorescence (middle column), and merged images of the two (right column). B) Distribution of QDs injected into the peritoneal space and imaged at 10 minutes, 20 minutes, 1, 4, and 24 hours after injection. Uptake into intraabdominal lymph nodes can predictably be seen 20 minutes after injection, and up to 24 hours after injection.

Figure 2. Imaging and Quantification of Peritoneal Lymph Flow Using Small Hydrodynamic Diameter HSA800

A) Examples of HSA800-positive lymph nodes (arrows) in each anatomic location. From top to bottom: Superior mesenteric, periportal, celiac, superior mediastinal and anterior mediastinal. Shown are the color video (left column), NIR fluorescence (middle column), and merged images of the two (right column). B) Distribution of HSA800 injected into the peritoneal space and imaged at 10 minutes, 20 minutes, 1, 4, and 24 hours later. Uptake into intraabdominal lymph nodes is seen reliably 20 minutes after injection and up to 24 hours after injection. Uptake of HSA800 into intrathoracic lymph nodes can be seen reliably 1 hour after injection and up to 24 hours after injection.

Figure 2. Imaging and Quantification of Peritoneal Lymph Flow Using Small Hydrodynamic Diameter HSA800

A) Examples of HSA800-positive lymph nodes (arrows) in each anatomic location. From top to bottom: Superior mesenteric, periportal, celiac, superior mediastinal and anterior mediastinal. Shown are the color video (left column), NIR fluorescence (middle column), and merged images of the two (right column). B) Distribution of HSA800 injected into the peritoneal space and imaged at 10 minutes, 20 minutes, 1, 4, and 24 hours later. Uptake into intraabdominal lymph nodes is seen reliably 20 minutes after injection and up to 24 hours after injection. Uptake of HSA800 into intrathoracic lymph nodes can be seen reliably 1 hour after injection and up to 24 hours after injection.

Figure 3. Location of Injection Does not Significantly Alter the Lymph Node Groups Identified

NIR fluorescent lymphatic tracers were injected into the right upper, left upper, right lower, or left lower quadrant and imaged 1 hour after injection A) There is no significant difference in the location of uptake of QDs, regardless of the intraperitoneal injection site. QDs, marking the sentinel lymph nodes, are seen within intraabdominal lymph nodes. B) There is no significant difference in the location of uptake of HSA800, regardless of injection site. HSA800, which identifies lymph flow beyond the sentinel lymph node, was seen within intraabdominal and intrathoracic lymph nodes one hour after injection into the peritoneal space.

Figure 4. Bowel Resection Alters Peritoneal Lymph Flow

A) Six rats receiving bowel resection, intraperitoneal QD injection, and imaging 1 hour later showed decreased QD uptake into intraabdominal lymph node groups and increased uptake into superior and anterior mediastinal lymph node groups compared to six sham surgery control rats. B) Six rats receiving bowel resection, HSA800 injection, and imaging 1 hour later showed increased uptake into superior and anterior mediastinal lymph node groups, elimination of uptake into periportal lymph node groups, and decreased celiac and superior mesenteric lymph node uptake compared to six control rats.

Figure 5. HSA800 Distribution Pre- and Post-Bowel Resection

A) HSA800 injected into the peritoneal space and imaged 1 hour later shows uptake into lymphatics of the diaphragm, the thoracic duct, and superior mediastinal lymph nodes in a sham control rat. B) After bowel resection from the ligament of Treitz to the descending colon and anastomosis, HSA800 was injected into the peritoneal space and imaged 1 hour later. HSA800 flow through the thoracic duct is eliminated, but enhanced parasternal lymphatic flow and superior mediastinal lymph node uptake is seen. Shown are the color video (left column), NIR fluorescence (middle column), and merged images of the two (right).

Figure 6. Flow of Lymph from the Peritoneal Space and Changes in Flow Post-Bowel Resection

Peritoneal lymph is directed to: 1) Intraabdominal SLN groups (superior mesenteric, periportal and celiac), 2) the thoracic duct, and 3) eventually mediastinal lymph nodes. Post-bowel resection, peritoneal lymph is directed to: 1) anterior chest wall lymphatics and 2) intrathoracic SLNs.