Persistent or chronic pain is complex, and to understand how it occurs you need to understand something about the different systems of the body and how they are involved. In this post I’ll examine the lymphatic-venous drainage system, explain what it is and set the scene for a more detailed look in an upcoming post about how it forms a key piece in the chronic pain puzzle.
The body is often considered to consist of several different systems which each have some unique functions. For example, the nervous system, integumentary system (the skin), the endocrine system (the glands which secrete hormones) and so on. The circulatory system most of us will be familiar with. It consists of:
The lungs which oxygenate our blood,
The heart which pumps our blood,
The arteries which take blood to the tissues,
and the veins which drain the tissues returning the de-oxygenated blood back to the lungs to start the process over again.
Hopefully I haven’t lost anyone yet.
Let’s look at bit closer at how each cell receives its nutrition and oxygen from the blood. As the arteries carry blood from the heart to the tissues, the initial artery starts out being a large diameter vessel, and progressively reduces in size as it gives off many branches along its course. This is rather like a tree starting with a trunk then branches, then twigs and so on. By the time the artery reaches the level of the cell, it has shrunken in size so much that it only allows a single red blood cell to pass through at a time – this vessel is now known as a capillary. To get oxygen or nutrients to the cell (or for that matter carbon dioxide and other waste products back into the capillary) these must all exit the capillary vessel and diffuse across the gelatinous space (“Interstitial fluid” or “interstitium”) between the vessel and the cells. Any fluids, cells or waste products making it back into the capillary keep on flowing back towards the heart, at which time the de-oxygenated blood enters progressively larger vessels known as veins. All pretty basic high school anatomy.
But what happens to any fluid or waste products that don’t automatically diffuse down their concentration gradients back into the capillary / venous system? This fluid and waste will sit around the outside of your cells leading to swelling and pain (chemical waste products tend to be inflammatory and about 3 litres of fluid per day fail to make it back to the venous drainage system). We normally don’t get swollen or inflamed and sore, simply because the body has another set of vessels called the lymphatic system which drains the extra-cellular space (ie drains the excess fluid and waste products around the outside of the cells that didn’t make it back into the venous circulation).
Lymphatic vessels are a little larger than a capillary and begin between cells as a blind tube only a single cell thick. The vessels gradually become larger, gain some valves much like veins to prevent backflow, and gradually develop a thicker vessel wall containing contractile smooth muscle (again like the veins and arteries).The vessels drain into a series of inter-connected lymph nodes which “filter and process” unwanted cells, bacteria, and viruses (hence the lymphatic system is an important part of your immune system). Eventually the lymphatic fluid is transported all the way to the base of your neck where they empty back into the great veins returning fluid to the pulmonary circulation ready to receive more oxygen. That’s right – even the fluid from the tips of your toes must make it up as high as your neck to prevent swelling.
Now you might be starting to see why the venous-lymphatic drainage system can be important in persistent pain.
Imagine that the system isn’t working quite right and some of the waste products are becoming trapped around your cells. I think of this as “an inflammatory swamp” around your cells, and inflammation causes pain! You don’t have to be swollen in a major way for inflammatory chemicals to be trapped – the lymph vessels are thin, delicate, and connected by microfilaments to the surrounding tissue, so any abnormal tissue tensions can reduce their drainage capacity leading to build up of inflammatory mediators in the extra-cellular space. This occurrence has been well documented in the literature on chronic pain. Treatment in situations where this occurs is analogous to “draining the swamp and replacing it with clear spring water”. Imagine how much better those painful cells begin to feel. I realise this is an analogy that might not sound scientific but read the upcoming posts and see how trapped inflammatory cytokines (for the scientifically minded) can perpetuate pain, and how this may be diagnosed and treated using a technique known as Fascial Counterstrain.
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