Oedema is a state of disease in which the tissues of a part become infiltrated or saturated with the watery constituents of the blood, causing more or less swelling of a soft, doughy character. It frequently occurs in the legs of horses, when they are said to "fill". This form of swelling, although sometimes considerable, is rarely attended with pain, and for the most part is soon dispersed, although liable to recur so long as the cause continues in existence.
Filling of the legs is brought about by many and various influences, but of these general weakness and want of condition are by far the most common. Hence it is noticed in animals after an attack of sickness, and especially if attended with long standing and want of rest, as in pneumonia, pleurisy, and some other disorders and accidents.
Heart-disease, by enfeebling the circulation, invariably gives rise to more or less swelling of the limbs, as do also occasionally functional derangements of the liver, the results of over-feeding and idleness. And the same may be said of functional and structural impairment of the kidneys, tending to the suppression of urine. Horses when first stabled after a run at grass are peculiarly liable to oedema, and it is very commonly associated with certain forms of influenza and fever. Horses which inherit a disposition to inflammatory oedema, or, as it is called, " Monday morning disease", are commonly the subjects of these less serious attacks of "filling of the legs ". Severe work over hard ground also provokes it in hunters and racers.
Ordinary filling of the legs presents itself as an enlargement between the pasterns and the knees in front, and the hocks behind. To the feeling, the swelling is doughy and "pits on pressure", i.e. a pit is left wherever the pressure of the fingers is applied. There is no considerable rise of temperature or pain in the part, and beyond slight stiffness the action is not interfered with.
The hind-legs, being farthest from the centre of circulation, are more subject to oedema than the fore ones, but it commonly occurs that all the extremities are more or less affected.
In a disease having its origin in so many and such diverse causes, it would be impossible to lay down any single course of treatment capable of meeting all its requirements. In those cases resulting from debility the aim and object should be to build up the system by a liberal diet, and impart tone to the body by the administration of vegetable and mineral tonics, of which nux vomica and sulphate of iron are the most appropriate. Gentle exercise daily will tend to disperse the swelling, and the liberty of a loose-box will greatly assist in preventing its return.
When oedema is the result of heart-disease there is little to be done calculated to effect any permanent good: regular and careful dieting, light work, an occasional aperient dose of aloes, and such measures as will improve the general health are best calculated to disperse and, as far as can be, control the swelling. Sudden and severe exertion and fatigue aggravate the mischief, and should therefore be carefully guarded against.
When the fault is traceable to derangement of the liver or digestive organs, a dose of physic, followed by a restricted diet and a course of alterative medicine, will suffice to restore the balance again. All cases of oedema are benefited by small repeated doses of nitrate of potash, and more especially so when the disorder arises out of the faulty action of the kidneys. Massage and vigorous rubbing, with the application of dry linen bandages to the legs, will prove serviceable. In some cases wet bandages and cold-water irrigation with exercise will have the desired effect when aided by a short course of diuretic medicine. This treatment is specially applicable to animals whose legs are weakened by hard wear.