Some Vessels in the Body Are Meant to Leak

When an ankle swells after a sprain, or a wound weeps clear fluid, most people assume a vessel has burst or grown weak.

That does happen. But what happens far more often is different. The body has opened the wall in that place for a while.

Vessel walls differ from place to place

The inside of a vessel is covered by a single layer of endothelial cells. How tightly those cells interlock differs from place to place.

• Vessels in the brain are unusually tight. The seams are locked so firmly that little gets through. This wall is called the blood-brain barrier.
• Vessels in hormone-secreting glands, the gut lining and the kidney have outright windows in them. These are places that must release quickly and filter quickly.
• Vessels in the liver are looser still. Even large molecules pass.

The tightness of a wall is matched to the work of that place. Somewhere that must be protected, like the brain, stays locked; somewhere that must exchange stays open. Neither is the better vessel.

Even a tight vessel opens when it must

This is the more important part. Tight vessels widen their gaps as the occasion demands.

With injury or inflammation, signals such as histamine appear in that place. Endothelial cells that receive the signal loosen the seams by which they had been holding each other. Gaps open between cell and cell, and fluid and protein pass through. White blood cells enter the tissue by the same gaps.

Swelling means this door has opened. Not that the wall gave way, but that the body gave the order to open. (The Swelling Is Gone but It Still Feels Stiff)

Without opening, nothing can be repaired

Why open at all? Because what the repair needs is inside the vessel.

The cells that fight, and the material to rebuild the wall, are in the blood. For them to reach the tissue, the wall has to open. Keep the door shut and the repair crew never arrives.

So swelling is not simply a bad thing. Early swelling is closer to a sign that work has begun.

Staying open for a long time is another matter. Protein that has left stays in the tissue, and water stays with it. The swelling does not settle, and the environment of that place itself changes. The problem is not the opening but the failure to close on time.

Closing is also something the body regulates

There is machinery on the closing side too.

One part of it is flow. The force of blood brushing past the wall is itself a signal to the endothelial cells. Where flow is steady, the wall holds in its settled state. The fuzzy layer coating the inner surface is where that flow is felt. (The Inner Surface of a Vessel Feels the Flow)

This is why moving is often better than keeping still when something is swollen. Flow has to return for the wall to tighten again and for what has left to be gathered into the lymph. Strenuous movement right after an injury is a separate matter and needs distinguishing.

So in practice

Looking at swelling, I separate whether it is opening now, or failing to close when it should.

If it is opening, I do not rush it. If it has not settled after several days, or is worse in the morning, or holds the mark of a finger for a long time, then I look at both closing and clearing. The same swelling can call for work in different places.

When to be seen first

If one leg alone swells suddenly and hurts, or the face and lips swell quickly along with difficulty breathing, examination comes first. If swelling on both sides persists, it is worth checking the heart, kidneys and liver once.

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There are this many branches to the single fact of swelling.

Korean medicine never treated swelling as something simply to be driven out. It asked when it began, how it feels under pressure, whether morning or evening is worse, and decided what came next from that. The same swelling was handled differently according to its timing.

Looking at it now, that makes sense. Opening and closing are different machinery, and swelling that is opening and swelling that has failed to close call for work in different places.

Knowing the mechanism makes the old examination's fine questions clearer, not quainter. I ask them as they are.

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Sources

• A review of how the tightness of vessel walls differs between organs, and how permeability is a regulated process rather than passive leakage — Upsala Journal of Medical Sciences, 2015
• A review of how signals such as histamine loosen the junctions between endothelial cells to open gaps, and how that opening is reversible and controlled — Pulmonary Circulation, 2014

Written by Dr. Heo Ji-young (Ph.D. in Korean Medicine Pathology, Kyung Hee University · former Research Professor of Herbology, Kyung Hee University)