DISEASES OF BLOOD-VESSELS Arteritis. Inflammation of the Arterial Walls.In the horse we may meet with two forms of arteritis, atheromatous and parasitic.
Arteritis obliterans as met with in the human subject is of rare occurrence in animals.
Atheroma is usually seen in or posterior to the arch of the aorta, but may affect any portion of the arterial system, notably the anterior mesenteric, . coronary, digital, and cerebral vessels. It is more common in aged horses.
The lesions of atheroma are only visible upon opening the artery and examining the inner surface of its walls. They may vary from shallow ulcers arising from the shedding of degenerated endothelial cells to raised calcified masses.
The earliest stage is cellular infiltration of the tunica intima. This takes the appearance of small raised, greyish-white spots of irregular size and shape. The infiltrated areas undergo fatty degeneration and may be shed with the formation of ulcers, but more commonly they become calcareous, owing to the deposition of lime salts. The lining of the vessel then bears small bony processes, usually of about the size of a barley grain but sometimes much larger. There are seldom any considerable number present in any area, though cases have been recorded in which the artery has been converted into a bony tube. This latter condition is more common amongst aged persons than amongst the lower animals.
The existence of these lesions in the arterial walls causes a lack of elasticity.
As a result of fatty degeneration aneurism may occur, owing to loss of elasticity and a tendency to stretch. The walls of the vessel, at first thickened and leathery in appearance, now become quite thin, and the tension within the degenerated walls may be sufficient to cause rupture.
There is also a possibility that death may occur from embolism, resulting from the entrance of cast - off degenerated tissue or fibrinous deposits into the blood stream.
Verminous arteritis denotes inflammation of the walls of an artery arising from invasion by worms. The commonest situation of the lesion is the anterior mesenteric artery, but the aorta itself is not uncommonly affected. The parasite responsible for these changes is Strongylus vulgaris (see"Parasites").
The invaded vessel at first becomes thickened, then degenerated, and assumes the appearance of wet chamois leather. Its elasticity is lost and so aneurism results. Fibrin becomes deposited upon the lining of the dilated vessel, and in this layer the parasites embed them selves. The final result of these changes is that the blood supply to portions of the bowel becomes diminished and the animal suffers from colic, diarrhoea, and emaciation. In colts particularly, similar changes may occur in the aorta and may produce symptoms of paraplegia. In cattle atheromatous arteritis occurring in the region of the aortic valves may accompany Johne's disease or other debilitating conditions. In dogs it is rather more frequently observed, and is particularly common in the large breeds.
Treatment of arteritis is more or less useless. The most that we can do is to attempt to maintain strength and energy by careful dieting and hamatinics when indicated. Digitalis may assist the heart to perform its increased labours.
Iodine has been recommended, and in vermin ous arteritis may be employed with advantage in thirty-grain doses, once daily, combined with nux vomica and digitalis.
Aneurism.Aneurism may be true or false.
A true aneurism is a circumscribed dilatation of the wall of an artery. Occasionally true aneurism of the heart wall is met with also.
A false aneurism arises from wounding of an artery without perforation of the skin. The vessel then bleeds into the areolar tissue, and thus a cavity may be produced the walls of which become smooth and fibrinous. Should the wound in the arterial wall remain per manently open, a false aneurism is produced and can be recognized by its pulsation.
A"dissecting aneurism"is said to exist when blood forces its way between the tunica intima and media.
True aneurism may be cylindrical, fusiform, or sacculated. It is more common in man than in the lower animals, with the exception of worm aneurism, which is very common among equines.
In the dog, aneurism of the posterior aorta occurs, particularly in old animals. When of considerable size, pulsation may be detected by palpation of the sub-lumbar region.
Aneurism is almost invariably the sequel to pre-existing disease of the vessel wall, and in the horse parasitic invasion is usually responsible.
Worm aneurisms are usually found in the anterior mesenteric artery and at its origin from the inferior aspect of the aorta at the first lumbar vertebra. They are frequently multiple, but rarely of any considerable size. Owing to the deposition of fibrin upon the inner surface of its walls and the presence of parasites, the swell ing differs from that seen in aneurism arising from other causes, in that pulsation is seldom discernible and the enlargement upon palpation appears almost solid. Aneurism of the aorta from the same cause is sometimes observed.
The dangers of worm aneurism are not to be disregarded. Rupture sometimes occurs, parti cularly during the early stages of the aneurism, but it is by no means common. Colic, diarrhoea, and emaciation may result from partial block ing of the anterior mesenteric artery, whilst complete obstruction of one of the smaller branches may occur from cast-off portions of the thrombus becoming lodged therein. By this means colic may be produced, lasting for days and terminating in necrosis of a small portion of intestine or by the establishment of collateral circulation. Recovery is, however, the rule, as before necrosis occurs the blood supply is usually partially restored by shrink ing of the thrombus. Particles of thrombus material often containing worms may also be come attached in other vessels, as the aorta, whilst portions detached from an aortic throm bus may beoome lodged in the iliac arteries.
The surgical treatment of aneurism is usually, owing to its situation, futile in equine and exceedingly difficult in canine patients. The administration of iodide of potash or iodine may be of some service in worm aneurism. Treatment must follow the lines laid down in the case of arteries.
Thrombosis.By the term thrombus we mean a blood-clot which has formed within the heart or blood-vessels during life.
A thrombus may therefore be cardiac, arterial, or venous.
The chief difficulty in post-mortem examina tion of an intravascular blood-clot is to deter mine whether coagulation took place after or prior to death. It is quite common to find large parti-coloured clots filling one of the cavities of the heart and extending into the large vessels, but it does not at all follow that coagulation occurred before death. The chief deciding point is the attachment between the coagulum and the endocardium, and it must not be inferred that blood-clots which are only with difficulty removed from the cavity of a ventricle are necessarily adherent and therefore of ante mortem occurrence, as entanglement with the chordm tendinew may lead to error.
Thrombi may be red, white, or parti-coloured. Red thrombi are composed of ordinary blood clot, white are fibrinous, whilst parti-coloured are mixed; sometimes this is due to infiltration of blood into a white fibrinous thrombus.
The causes of thrombosis may be injury to or disease of the endothelium, or the detach ment of particles of other thrombi which be come lodged in another vessel (embolism) and form the nucleus for the formation of a fresh thrombus.
Injury to the lining of a vessel from contusion, stretching, wounding, infection, etc., results in the deposition of blood-platelets and leucocytes at that spot. These apparently develop that elusive body termed"pro-thrombin,"which in the presence of lime salts produces thrombin, the resulting coagulation of blood giving rise to local obstruction of the vessel, which may be partial or complete.
Thrombi are more commonly met with in veins than in arteries, as these vessels possess thin walls which are more liable to injury and the circulation within them is more liable to become stagnant.
Thrombi tend to shrink, and so a vessel totally occluded may again become moderately useful with a small passage for the flow of blood. Indeed, at a later stage the whole thrombus may become absorbed, provided that it has not been of any great size. As a rule, however, calcification occurs with the production of"phlebolites"or vein stones, or the thrombus may become organized and fibrous.
Infected thrombi usually disintegrate and give rise to embolism or pywmia.
Iliac Thrombosis. Thrombosis occurring in the iliac arteries or at their point of origin from the posterior aorta is by no means rare in horses. A similar condition is sometimes met with in the brachial artery and produces symptoms in the fore limb similar to those caused by iliac thrombosis in the hind ones.
The deposition of fibrin may commence in the terminal portion of the aorta or in any one of the four iliac arteries. When the former is the case the clot usually extends into each of the iliacs in addition. The vessel is at first only slightly obstructed, so that the onset of symp toms may be gradual. At first the occlusion of the artery is only partial, but it may become complete. As a rule symptoms appear, gradu ally reach a maximum intensity, and then become rather less severe but permanent as shrinkage occurs in the thrombus. A thrombus once developed is seldom, if ever, absorbed, although portions may become detached and produce embolism lower down in the limb.
The causes of iliac thrombosis are not very clearly understood in all cases. Possibly strongyles are responsible in some cases; in fact they have been found in the thrombi on post-mortem examination in a few cases. Some veterinarians regard the condition as occurring as the result of changes in the endothelium, arising from the presence of the toxins of influenza, strangles, etc., but it is difficult to conceive why such a limited area and so con stant a position should be attacked.
The symptoms are very characteristic. At rest the animal shows nothing unusual, and when the thrombus is of small size lameness may not become evident until the horse has been trotting for several minutes. The lame ness may be more apparent whilst the limb is being advanced or whilst at rest. In the former case the thrombus usually lies in the femoral artery and causes deficiency of blood supply to the extensor muscles; in the latter the thrombus usually lies in the external iliac artery and cuts off the blood supply to the gluteal muscles and to the quadriceps femoris.
The leg is then unable to bear weight, as all the lower articulations become flexed and the symptoms then resemble those of crural paralysis, excepting that there is evidence of severe pain upon exercise and no disability on the part of the animal whilst at rest in the stable.
Sometimes the condition is bilateral, and in a few cases recorded the thrombus has been capable of moving across the aorta from one iliac artery to another.
The lameness is accompanied by severe pain when exercise is forced. The animal sweats profusely, whilst the affected limb remains dry; he looks round anxiously at his hind quarters, and if forced to continue his pace, eventually falls to the ground.
In thrombosis of the aorta or bilateral iliac thrombosis the animal can frequently remain standing for short periods only. Sometimes cardiac disorders occur in conjunction with the condition, owing to increased opposition to the heart's impulse. The veins of the limb are also engorged, as there is less pressure from behind to force the blood upwards on its way to the heart.
Diagnosis can be confirmed by rectal explora tion and by lack of pulsation in the arteries as compared with those of the opposite limb.
Treatment. As the only hope of recovery lies in either the establishment of collateral circulation or absorption of the thrombus, exercise must be continued daily until lameness appears and then ceased until the animal can again proceed without pain. Potassium iodide may be employed internally, and thiosinamine preparations might be given a trial by intra muscular injection.
Treatment is, however, almost invariably futile.
Phlebitis.Inflammation of a vein is much more commonly met with than is arteritis, as veins have thin walls, are more superficially situated, and are therefore more prone to injury.
Since the passing of the days when bleeding from the jugular vein was considered in dispensable to the treatment of animal ills, phlebitis has become much less common.
The cause is usually injury, and in the majority of cases wounding of the vein precedes phlebitis. There are two recognized forms: (i.) simple phlebitis; (ii.) suppurative phlebitis. The result of injury to the wall of the vein is the formation of a thrombus within its lumen. The degree of infection occurring at the time of injury and during the process of healing will decide whether the thrombus will remain sterile or will break down and form pus. When the breach in the wall of the vein does not close immediately after the infliction of the wound, and particularly when a blood-clot forms between the skin wound and the vein, infection is almost sure to follow.
Injuries to the jugular region unassociated with actual wounding may result in peri-phlebitis and possibly in aseptic thrombus formation with a risk of embolism.
Symptoms. The skin wound instead of uniting by first intention discharges a serous or sanguin olent fluid. Local swelling increases until the lips, face, and sternal region appear deformed in severe cases. The jugular vein can be felt hard and cord-like, owing to the presence of a throm bus within it. After a few days, should infection be not very virulent, the swelling will subside, collateral circulation will be established, or the other vein will perform increased work and the thrombus will contract, drawing the vessel with it into a thin cord. Thrombus formation can always be detected by inability to"raise"the jugular by pressure on it near the chest. Some times a small passage may be left in the vein after contraction of the thrombus has occurred.
If infection be severe the swelling will not diminish, but pus formation will develop within the thrombus and at the seat of the wound, whilst by extension to the outer coat of the vein suppuration will occur at various parts of the jugular furrow and thrombus formation may extend up the vessel for a considerable distance. Sometimes broken-down portions of thrombus from the lower end of the vessel become carried into the circulation and cause embolism, or pymmia may result from the dissemination of pus organisms by the circulation.
Treatment. Simple phlebitis requires hot fomentations along the course of the vein and the application of iodine tincture to the skin wound. A dose of physic and a course of mashes must also be provided. The occluded vein should not be probed or otherwise interfered with, and no treatment is likely to render it patent.
Septic phlebitis requires drainage, though in cases where it is possible to locate the ends of the thrombus the vein should be ligatured both above and below it. It may then be opened for an inch in length at several points between the ligatures, or a long probe may be passed through it and may be used to draw through its length a perforated rubber drainage tube through which antiseptics may be injected daily. Some practi tioners prefer to remove the vein. This may usually be accomplished by dividing the vein below the ligature after longitudinal section of the skin of the jugular furrow and exerting moderate traction.
Phlebolites or vein stones are calcareous thrombi composed of phosphates of lime and magnesia, sometimes found in dilated veins.
Varix.Varicose veins are very uncommon in the domesticated animals.
The saphena vein sometimes shows dilatation, the so-called blood spavin. We have observed a mass of varicose veins as large as a cocoa-nut beneath the skin covering the extensor muscles of a mule just above the hock.
Operation was attempted, but it was found impossible to locate the vessel, which filled the varix, and although needles were inserted deeply and tight ligatures applied over them, the vessels filled as before. On post-mortem the limb was found honeycombed in this region with thin walled vessels the diameter of a penny which branched in all directions. Pressure on the saphena and metatarsal veins produced no diminution in the size of the enlargement during life.
Varicocele is met with in many stallions, particularly those of advanced age. Castration is the only remedy, and it will usually be found necessary to ligature the veins separately, as the cautery does not stop the flow of blood backwards past the valves, which are rendered useless by the dilatation of the vessels.
Haemorrhoids. Piles. These are very rarely seen in the larger domesticated animals, though they occasionally occur in old, fat dogs. Ex ternal piles may be removed by ligature. In the horse, and particularly in the mule, folds of mucous membrane of the 'rectum may project through the anus and become congested from becoming trapped in the sphincter and from exposure to the air. This induces straining and aggravates the condition. These are not true piles, but they produce similar symptoms. If ligatured, prolapse of the rectum may occur from straining, and unless they cause serious inconvenience it will be found advisable to leave treatment alone. Sometimes bathing with as tringents may be beneficial, although relief may be only temporary. A severe case in a mule was treated under chloroform by drawing out the first inch of the rectum by traction on the mucous folds and subsequently performing am putation after inserting multiple ligatures. For the first three days defmcation was assisted by clysters. The animal returned to work on the ninth day, healing being complete.
Rupture of Blood-vessels. Rupture of the anterior mesenteric artery may occur as the result of aneurism formation arising from the presence of strongyles. It is not a common happening, but we have observed two cases in colts. Both animals were found dead. Internal haemorrhage may accompany various con gestive conditions. Bleeding from branches of the pulmonary arteries is sometimes met with in horses affected with chronic emphysema of the lung tissue. We have observed two cases in each of which haemorrhage ceased, but was renewed on the following day with fatal con sequences.
Haemorrhage from the nasal cavity (epistaxis) may arise from over-exertion, as in racehorses, with fatal results in rare instances. Haemo rrhage is likely to recur with violent exercise.
Sudden violent haemorrhage is accompanied by rapid blanching of the visible mucous mem branes, depression, sighing respiration, yawning, and finally rambling movements, decubitus, and death. Dogs and cats may die within two minutes from rupture of the aorta following external violence.
The treatment of most service is the hypo dermic administration of a large dose of atropin.
Adrenalin injected hypodermically is also useful as a preventive. Cold water may be thrown over the animal as an emergency measure, some times with good results.
Lymphangitis. This is almost invariably the result of the admission of either bacteria or bacterial products into the lumen of the lymph atic vessels. The diseased condition extends in a centripetal direction, as from the foot when the subject of bacterial invasion, upwards towards the thigh or shoulder. The lymph vessels them selves become both dilated and thickened, so that they are easily visible beneath the skin in an acute attack, but chronic lymphangitis is usually associated with marked thickening of the skin, so that the course of the vessels is masked, even when they are greatly dilated.
In severe or prolonged cases inflammatory changes extend beyond the walls of the lymph vessels, with congestion of the capillaries and extravasation into the subcutaneous tissues.
Lymphangitis is almost invariably a complica tion of septic wounds of the extremity, and is also particularly common in connection with wounds of the trunk caused by friction of the harness. Punctured soles and nail pricks may be attended by lymphangitis extending as far as the thigh or armpit.
The distension of the lymph vessels usually extends as far in a centripetal direction as the nearest group of lymphatic glands. Sometimes suppuration occurs in these and also at various points on the course of the vessels, and occa sionally the resulting changes so diminish the efficiency of the glands that pus-organisms find their way into the general circulation and thereby set up premia.
It is not uncommon to see successive small abscesses develop on the course of a lymphatic vessel as the result of a foot injury or of a tread or wound of the heel or coronet. Each abscess appears at a somewhat higher level than the last, until the axilla or thigh is reached, when the glands usually become involved in the suppurative process.
In cattle, tuberculous deposits sometimes occur in the limbs, appearing as chains of small swellings the size of a hazel nut or sometimes of a walnut. If incised a soft caseous material exudes, and in long-standing cases gritty par ticks are present, or the whole mass of material may be calcareous. Tubercle bacilli are visible in the cheesy matter upon microscopical ex amination. The condition is not attended by local inflammation.
Treatment. Internally iodide of potash and biniodide of mercury may be prescribed with good results, whilst elimination should be accelerated by aperients and diuretics. In chronic cases iodide of iron with arsenic or Donovan's solution may be employed. In suppurative lymphangitis intramuscular injec tion of nuclein solution may be beneficial, and when possible an autogenous vaccine should be made use of.
Locally hot fomentations and massage in a centripetal direction assist the flow of lymph, whilst subsequent light friction with a liniment containing camphor and belladonna diminishes the pain and soreness.
The sheet-anchor of treatment, however, lies in thorough disinfection of the wound. Wounds of the foot should be thoroughly pared out and dressed with 10 per cent solution of perchloride of mercury in spirit. Other wounds may be well curetted and dressed with suitable anti septics or plugged with powdered permanganate of potash, which gives excellent results.
Suppurating centres should be freely opened and treated with antiseptics. R. H. S.