Research that impacts anastomosis surgery

Binney4

Hi, all you research buffs!

The new year starts off with the study below that looked at how our lymph systems return lymph fluid safely to the venous system. Since it's a subject that has potential implications for lymphovenous anastomosis surgeries, I thought some of you might be interested:

Title: Platelets mediate lymphovenous hemostasis to maintain blood-lymphatic separation throughout life

Author(s): Paul R. Hess, David R. Rawnsley, Zoltán Jakus, Yiqing Yang, Daniel T. Sweet, Jianxin Fu, Brett Herzog, MinMin Lu, Bernhard Nieswandt, Guillermo Oliver, Taija Makinen, Lijun Xia, Mark L. Kahn

Abstract:

Mammals transport blood through a high-pressure, closed vascular network and lymph through a low-pressure, open vascular network. These vascular networks connect at the lymphovenous (LV) junction, where lymph drains into blood and an LV valve (LVV) prevents backflow of blood into lymphatic vessels. Here we describe an essential role for platelets in preventing blood from entering the lymphatic system at the LV junction. Loss of CLEC2, a receptor that activates platelets in response to lymphatic endothelial cells, resulted in backfilling of the lymphatic network with blood from the thoracic duct (TD) in both neonatal and mature mice. Fibrin-containing platelet thrombi were observed at the LVV and in the terminal TD in wild-type mice, but not Clec2-deficient mice. Analysis of mice lacking LVVs or lymphatic valves revealed that platelet-mediated thrombus formation limits LV backflow under conditions of impaired valve function. Examination of mice lacking integrin-mediated platelet aggregation indicated that platelet aggregation stabilizes thrombi that form in the lymphatic vascular environment to prevent retrograde blood flow. Collectively, these studies unveil a newly recognized form of hemostasis that functions with the LVV to safeguard the lymphatic vascular network throughout life.

The full article can be seen online at http://www.jci.org/articles/view/70422#share

After I read the full article I emailed one of the researches and asked him if they had any theories about how this information might relate to short- or long-term side effects of anastomosis surgery. Here's his reply: [Note: the word "thrombose" means to obstruct with a blood clot.] 

You raise one of many points that have come to our minds after this discovery. We are actively collaborating with pediatric and adult clinicians at Penn to address this point. Empirically, these anastomoses seem to help, but there is a lack of controlled trials. The obvious concern is that any connection, esp one that lacks a natural valve, will allow blood to encounter lymphatic endothelium and activate platelets as we have described. It is possible that this mechanism operates in a good, protective way for anastomoses just as we assume it does at the natural lymph-venous junction. It is also possible that these anastomoses thrombose soon after they are made and do not provide lymphatic drainage. I think high quality ultrasound and MRI imaging of these anastomoses would be indicated to address this question.

Hope some of that helps those of you weighing surgery options. I wish we had better research and this wasn't all guesswork! Be well,
Binney