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Is it really fibrosis? Or is it thixotropic tissue change?

Updated: Feb 25, 2022

I had an email recently from a therapist who described her client as having deep #pitting_oedema and heavy #fibrosis. Technically this is not possible. If the tissue is truly fibrotic then it really doesn't pit much any more. But in many ways they look and feel the same. So what is the difference and how can you tell which is which?

The #loose_connective_tissue is a complex and fascinating part of our bodies. Since every cell in your body relies on it for nutrient supply and waste removal, it is often referred to as the #connective_tissue_bath, and you can think of it like a bathtub. Imagine that every cell in your body is living in this nice warm watery bath. The blood vessels are like the tap - constantly supplying fresh, nutrient rich fluid to bathe the cells - and the #lymphatic vessels are like the drain, always removing the 'grey water', the waste products of cellular metabolism and anything that could be harmful to your cells such as invading micro-organisms.

Normally, what comes into the bath from the tap equals what goes out via the drain and all is hunky dory for your body cells, they get a nice clean environment to live in. But what happens when the lymph vessels can't do their job properly? The #extracellular_fluid begins to accumulate in the 'bath' and a lymph-oedema forms. And it is not just water, it's everything else that would normally be carried away by the lymph vessels. This includes those invading microorganisms and the immune cells that are protecting you from them, but more importantly for our discussion on fibrosis, it is the accumulation of #circulating_proteins that cause the problems.

There are hundreds of different types of proteins circulating through the loose connective tissue, hence the collective name, circulating proteins. Many of them are carrying hormones and other #macromolecules that your cells need to function. After delivering their 'load' to the cells, they leave the tissue via the lymphatic system and re-circulate back to the veins. It is important to realise that this is a one way street for these circulating proteins. They are too big to pass across the capillary wall so the #endothelial_cells that line the capillaries deliberately pass them out of the blood and into the tissue by a process called transcytosis.

Image downloaded from Google Images

And they can't go back the other way, they are a part of the #lymph_obligatory_load that is, everything in the extracellular compartment that must be removed by the #lymphatic_system. So if the drain is not working properly these circulating protein begin to accumulate in the tissue spaces of the extracellular compartment where they affect the structure and function of this important 'bathtub' that your cells are living in.

The extracellular matrix is composed of many elements. The actual composition will depend on what particular piece of tissue we are talking about. If we're talking about the thin layer of loose connective tissue that surrounds every single muscle fibre then we won't see any fat cells and few immune elements in there. In contrast, if we are looking at the loose connective tissue that forms the fatty insulating layer under skin, then we will see lots of fat cells and immune elements.

This image gives us an idea of all the things that we might see in the loose connective tissue

but does not represent any particular tissue location.

Regardless of where the loose connective tissue is located there will be some features that are always there. Fibres - collagen elastin and reticular fibres, immune cells such as macrophages, and the ground substance - big glycosaminoglycan molecules, in particular #hyaluronic_acid. These big molecules have the property of taking up and releasing water and hyaluronic acid in particular imparts the property if #thixotropy. Thixotropy is the ability to shift between a sol and a gel - that is the connective tissue environment can be more watery - the sol state, or more like a jelly - the gel state. This property of #thixotropic enables the ground substance to take up or release water, it's an important function and ensures that there is just the right amount of fluid in the bathtub to protect your cells against dehydration.

Excess proteins in the extracellular compartment affect this thixotropic state, driving it toward the gel end of the spectrum. In our bathtub analogy, the bathwater begins to become more like a jelly than a nice watery environment, and that's not healthy for your cells. Respiratory gasses, oxygen and carbon dioxide, take longer to exchange through the gel and the supply of other nutrients and removal of waste products also slows down. Now the cells are living in a gluggy, congested environment.

Image of pitting oedema from Pinterest

Its happening imperceptibly in latent lymphoedema - the tissues haven't visibly swelled yet - and it's what makes the early stages of overt lymphoedema feel firm. It has a different feeling to an acute swelling like in an ankle sprain which is a lot of tight painful fluid and usually looks shiny and a bit red. A high protein oedema is more like the kind of swelling in your ankles after a long flight, its heavy and if you press on it the dents stay there for awhile.

So what is fibrosis then? As you can imagine the body doesn't like all these proteins sitting in the bathtub turning the water to jelly. So it sends in the immune system - #macrophages in particular. They try to remove the proteins but here's the catch - movement through the connective tissue for immune cells is also a one way street, they can get out of the blood vessels and into the tissue spaces. They are also obligatory load - they have to get out via the lymph system. So now we have too many proteins and too many macrophages and a low level inflammatory environment. Inflammation makes fibrocytes - the cells that are making all the connective tissue fibres - produce more collagen. Double whammy, a high protein environment also stimulates the fiobocytes to make more collagen fibres. So if the high protein, inflammatory environment persists the jelly is turned to fibrous material. By now there is not so much free fluid, its all new connective tissue, including accumulating fatty tissue. So pressing on the oedema doesn't make the same pit, or only a shallow looking pit rather than a deep pit. The tissue is more like a sponge now and bounces back after the pressure is removed. Another clue is how long has the oedema been present? Fibrosis takes months and years to accumulate, a protein rich edema can occur very quickly.

It is important to recognise these differences as they make a big difference in how you develop your treatment plan and the results that you can expect to achieve. Pitting oedema is relatively easy to remove with MLD and standard #multilayer_compression. Fibrosis takes more effort to break down and requires the use of fibrosis techniques and 'chocolate' style pads or fibrosis mits under the bandages. Low-level laser or vibration devices can also help. You also have to give the tissue a longer time under compression to establish any kind of change in the connective tissue, the tissue needs time for tissue turn-over, so the course of bandaging will generally need to be longer.

This all adds up to what we already know - the earlier we treat lymphoedema the better! If we can get it under control in the early 'pitting' stages, we can prevent fibrosis form forming.

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