Stocking up is a familiar term to many horse owners and often is used to refer to a horse that exhibits leg swelling. The exact cause of the swelling can be variable and with this, so can the prescribed treatment course. The more we understand, often the better we can assist these patients, but it is a complicated problem in the equine industry.
One of the most common scenarios amongst horse owners is to have a horse that stocks up or swells up in one or more legs, especially after stall rest or even one night of confinement. Terms including lymphedema, lymphangitis, cellulitus are commonly used, having similar clinical findiings but different origins. We have many remedies for these situaitons, but often the problem persists despite, coming and going with moderate variability. In order to understand the problem, we must have a deeper look at anatomy and physiology.
Blood travels to the horse's limbs via arteries, delivering oxygen and nutrients to the tissues, then returns back to the heart via veins. The blood in the arteries is under pressure, which is determined by the heart rate, vascular resistance of the blood vessel and blood fluid volume. This pressure drops once the blood begins to return to the heart in the veins. Given the lack of significant pressure to assist the flow back to the heart, it is generally accepted that movement and pressure within the equine foot, actually serves as a heart, helping to pump the blood back up the leg. Horses are often referred to as having 5 hearts, implying a true heart in the chest and one heart per foot.
Fluid tends to shift out of the blood vessels, nourishing the tissues as part of normal physiologic processes. In some cases, due to poor return of blood via the veins to the heart, fluid can back up in the blood vessels, and begin to actually 'weap' out into the surrounding tissue, adding more fluid to the equation. In either case, most of this fluid outside of the blood vessels is generally taken up by the lymphatics, which are similar to blood vessels, and then returned back to the heart to be rejoined with normal blood circulation.
When we have a horse with a swollen leg, in most cases this implies that fluid has accumulated in the tissue outside of the blood vessels. Often, we will use the term 'edema' to refer to this fluid accumulation. If we put pressure to the swollen tissue or leg with our thumb, it will often leave an indendation, almost like mashing dough. The leg or swollen area will also be tight, but in regards to overt pain, it can be variable. So, we know that when we have a swollen leg, it is fluid accumulation, technically stocking up, but the cause is not always the same.
The term "Lymphangitis" refers to overt inflammation within the lymphatic system, leading to non-functional or compromised lymphatics, often blocked or damaged. This inflammatory process then impairs normal fluid circulation by the lymphatics and in the end, fluid pressure builds within the lymphatics and then weaps out into the surrounding tissue. Lymphangitis is not only an inflammatory process but usually connected with a bacterial infection. Advanced cases of Strangles in the horse can lead to lymphangitis as can other bacterial infections.
The term "cellulitis" refers to inflammation within the soft tissue of the leg, including muscle tissue. This condition is often secondary to a wound or spread of a bacterial infection from another location within the body. Again, here we have inflammation and infection in most cases, but involving soft tissue structures. The swelling within the soft tissue actually can impair blood and lymphatic circulation, just from shear constriction, leading to increased pressures and poor blood and fluid flow. The category of cellulitis to me also includes general wounds to the leg, which can be lacerations or even soft tissue injuries. Dependent on the extent of these injuries, blood vessels and/or lymphatics can be involved with resultant damage. Inevitably, this leads to fluid accumulation outside of the lymphatics and blood vessels, leading to the swollen leg.
The term "lymphedema' is a general term to imply fluid accumulation or retention, without an inflammatory or infectious cause, leading to a stocked up appearance or swollen leg. These patients are usually chronic, stocking up after a night's stay in the stall, no pain or lameness but resolving after turnout or increased work.
There are other causes of fluid accumulation or edema in the legs. Again, we have to remember that we are dealing with the cardiovascular system and fluid which abides by certain physiological laws of nature. First, if the heart is not functioning correctly or there is overall poor circulation within that horse, fluid will likely accumulate as a result. Second, fluid is retained within blood vessels based on oncotic pressure, which is dicated by certain proteins including one in particular called albumin. Albumin generally holds fluid within the blood vessels and when albumin levels drop, for whatever reason, fluid generally will leak out of the vessels into the surrounding tissue. Albumin is a protein made by the liver from protein taken in from the diet. In cases of liver problems, severe infection, endotoxemia, low protein diets and starvation, it is not uncommon to find swollen legs. However, in cases of low albumin, we will also generally see fluid accumulation on the underside of the belly and sheath region in geldings.
All cases of fluid retention in the legs often improve with movement and pressure wraps. Movement helps to increase heart rate and increases the rate of return of blood and fluid back to the heart. The more efficient the cardiovascular system, the more fluid that is absorbed and removed from the tissue space. Through movement, we are also moving the feet at a more rapid pace, which in turn helps to force blood and fluid back up the leg and towards the heart.
Pressure wraps also assist the problem in two ways. First, they help to force fluid in the soft tissue space back into the lymphatics and general circulation. Second, through their pressure, they also help to minimize fluid loss from the lymphatics and blood vessels. Caution should be noted in cases of impaired circulation however, as with too tight of a wrap or too prolonged use, one could actually impair or cut off circulation to the lower leg and digit. In most cases, pressure wraps are applied for 10-12 hours at a time, then off for 10-12 hours.
Water therapy is also helpful in many of these cases. In cases of infection and/or inflammation, cold hose water therapy is general very helpful at reducing some of the heat from the leg and pushing fluid back into the circulation. In cases of plain lymphedema, warm water therapy is more effective in my experience as often these cases are due to poor overall circulation and the added warmth appears to help improve or enhance circulation. This is analagous to cold hands in the winter time, which are often then pale in color. The cold temperatures actually make a weak circulation even weaker, disrupting and impairing blood flow, but if we add heat through gloves or otherwise, circulation is then enhanced, tissues warm up and color gets better.
Topical therapies are also helpful, often including DMSO alone or combined with a steroid. DMSO is a great anti-inflammatory and antioxidant with tremendous healing potential. It many cases, it is combined with a steroid to help boost anti-inflammatory properties and used as 'sweat' under a breathable wrap. Usually, the sweat is applied for 10-12 hours, then removed for the next 10-12 hours along with cold or warm hose therapy.
In cases of inflammation and infection, often oral or injectable anti-inflammatory medications are also used along with appropriate antibiotics.
Outcomes and Options:
In most cases of infectious lymphangitis and cellulitis, the horses respond nicely and are not impacted negatively in the future. However, in some cases, long term damage is done to the blood vessels, overall circulation and lymphatics due to the infection and uncontrolled inflammatory response. This can then lead to a long term tendency for fluid retention in that leg which can be difficult to manage.
I believe that cases of uncomplicated lymphedema are usually the result of overall poor circulation. It is important in these cases to rule out liver problems via blood work and to evaluate the heart and blood pressure if possible. It is not uncommon to have older patients develop lymphedema as often with age, circulation and heart function becomes impaired on certain levels, impacting fluid circulation. I do think that in these cases, if there are no other health problems, they benefit from nightly standing wraps if stalled but ideally respond best to constant turnout where movement is encouraged.
Are there other options and means of controlling the problem? I think there is.
In our cases of lymphangitis and cellulitus, we will often combine our Cur-OST EQ Plus or EQ Total Support with the EQ Immune & Repair formula, running the combination for 90 days. Through this combined approach, we are able to help balance the inflammatory response and enhance the immune response, aiding potentially with clearing of the infection. It is not uncommon in these cases to have an unresolved infection persist for months to years with a likewise swollen leg and impaired fluid circulation. Even in these chronic cases, I have found the combined regimen of Cur-OST formulas has made a huge difference, especially when combined with topical sweat therapies.
Chronic lymphedema cases can prove more difficult. There are several thoughts on these cases, as again, they are usually associated with overall poor circulation. Assuming that liver and cardiovascular function is normal, we have found a few regimens have been helpful. Many cardiovascular and circulation problems in humans have been noted to be strongly associated with inflammation on many levels. Persistent inflammation in the body can impair circulation by altering the function of nitric oxide, which is a gas produced by the body which dilates and opens blood vessels. I have found that the use of our Cur-OST EQ Total or EQ Plus can benefit these cases, helping again to balance the inflammatory response. Considering that we are looking to improve nitric oxide levels to enhance circulation, the EQ Immune or EQ Nourish formula have also proven beneficial due to the amino acids present, especially L-arginine, which is used by the body to produce nitric oxide. The other amino acids present in those formulas also help to maintain overall cellular health and may help to reduce leakiness within blood vessels. I will use the EQ Immune formula if I believe there is an immune component to the problem, but otherwise, I will use the EQ Nourish blend. The other added benefit to the EQ Nourish is the added pea protein which can support production of albumin by the body, but also the Co-Enzyme Q10 and alpha lipoic acid, which may also benefit overall cellular function and support the cardiovascular system.
We are working on a research formula at this time and using in a couple of cases of chronic lymphedema. This trial formula takes a different approach but is combined currently with our EQ Total or EQ Plus formula. The new approach is one which 'warms' the circulation and provides an alternative method for nitric oxide production in the body, which in turn helps to enhance circulation. In some cases, the amino acid L-arginine is not well utilized by the body for production of nitric oxide, so an alternative pathway is preferred. At this point, our data is premature but so far, the patients are responding nicely in more ways than one.
In the end, stocking up in the horse is a frustrating condition but a result of many possible origins or causes. Given the numerous causes and considering long term lingering damage from prior conditions, the options for therapy are really endless. Sometimes, though, as much as we wish for the first therapy to be the winning ticket, it doesn't work out that way and more investigative work is needed to explore other options.
I hope this information helps.
Tom Schell, D.V.M.
Nouvelle Research, Inc.