GOUT. PODAGRA. ARTHRITIS URICA.
Definition. Affects birds, dogs, perhaps pigs. Causes: excess of nitrogenous food, imperfect oxidation, impaired metabolism and elimination. Susceptibility of birds in confinement. Xanthin bases. Nuclein. Hepatic torpor. Contracted kidney. Affects tissues of little vascularity. Lesions: chalky deposits around joints, and in internal organs. Solubility of biurate of soda in synovia, serum, etc. Symptoms: arthritis, joint tenderness, resting on breast, hard or fluctuating swellings, desquamation, ulceration, chalky urates. Diagnosis: test for biurate. Treatment: less albuminoid diet, eliminating salts, colchicum, piperazin, surgical and antiseptic dressing.
Definition. An arthritis characterized by periodical exacerbations, by the deposit of sodium biurate in and around the joints and at times in other parts of the body, and by more or less constitutional febrile disturbance during the paroxysms.
Animals susceptible. Among the lower animals the disease has been noticed almost exclusively in birds, which even normally excrete so much uric acid that the liquid may be semi-solid as found in the cloaca or in the droppings. While this is a constitutional peculiarity in the bird yet it is enhanced in connection with an abundant diet of rich nitrogenous materials, as in forced feeding, and in old animals in which the eliminating action of the kidneys is more or less impaired. Ebstein has shown that gout can be produced in birds by tying the ureters. All domesticated birds, chickens, turkeys, pigeons, ostriches, geese, ducks, Guinea fowl, have been found to suffer. A case of gout has been reported in a dog, and Pradal has described it as existing in swine, but the symptoms given are more in accord with articular rheumatism.
Causes. The causes of gout are overfeeding especially on highly concentrated nitrogenous food, acid sweets, and in turn sweet and acid alcoholic drinks, an excess of uric acid in the blood and tissues, imperfect oxidation of albuminoids, impaired metabolism, imperfect elimination of uric acid, and impaired innervation. Probably no single morbid condition is in itself sufficient to induce the disease but a combination of several, unquestionably operate in many cases.
The uric acid theory is favored by the constant presence of this acid in considerable amount in the blood of birds, and by Ebstein’s experiment in tying the ureters, but it has to face the fact that young and active birds living in the open air, and hunting for their food do not suffer, that it is usually scanty in the blood of man just before an attack, that Gilman Thompson failed to produce any symptoms of gout by injecting into the blood of animals more uric acid than the amount which they normally excrete in twenty-four hours, that the familiar symptoms of uric acid poisoning are not at all those of gout, and that the excess of uric acid in leucæmia, anæmia and pneumonia produces no such symptoms. In addition to excess of uric acid some other factor is required.
Xanthin bases (Xanthin, hypoxanthin, etc.) found in the blood by various observers, are derived from albuminoids, especially nuclein and nuclein bases, including in man caffein and theine, and being closely allied to uric acid are believed to have a nearly similar action.
Various forms of abnormal metabolism are invoked as the cause of uric acid and gout, and Haig and Vaughan hazard the theory that the breaking down of the nuclein is an important factor. This and other metabolisms are attributed to the local action of the uric acid and urates, and again to a fault in innervation. The imperfect action of the liver where the uric acid should be largely resolved into the more soluble urea, and of the kidneys through which it should be promptly excreted must be attributed to a nervous source. Levison incriminates the granular, contracted, inactive kidneys.
Ebstein attaches great importance to impaired nutrition in the affected tissues which undergo necrotic changes that pave the way for the deposition of urates in their substance. This is somewhat sustained by the occurrence of the local deposits in tissues in which circulation and nutritive changes are slow, and in older animals in which not only are the osseous tissues more calcic and less vascular, but the articular lamella has been formed by cretefaction of the bone and cartilage. Haig suggests that in the old, the joints are less vascular and less alkaline, and more sensitive to cold. On the other hand those in the greatest vigor of life are more ravenous, digest more actively and are in this sense more subject to injury from excess of uric acid and allied products. Birds at this age, confined and in process of fattening are thereby exposed. Overfed, obese, lazy, old house dogs are under similar causative conditions.
Lesions. The most prominent lesions in birds are chalky concretions of urates on the articular ends of the bones and in the structures around the joints including even the tendons, with more or less inflammatory exudate and even necrosis, invading the bony tissue and articular cartilage. Abscesses may be present usually outside the bursa. Birds suffer especially in the tarsal, metatarsal and phlangeal joints, but often also in the corresponding joints of the wing, and less frequently in the joints of the trunk, and in the internal organs,—kidneys, liver, lungs, serosæ,—and skin. In these last, miliary chalky concretions and encrustations are found. In Brückmüller’s case in the dog the chalky deposits of urates were found mainly on the epiphyses of the ribs, but also on the joints of the limbs.
Uric acid is always abundant in the blood of birds, and Roberts has shown that biurate of soda (the usual form of precipitate) is insoluble in blood serum, synovia and other body fluids when in excess of 1:10,000.
Symptoms. In birds the febrile and constitutional symptoms have not been carefully observed so that the objective symptoms in the affected joints have been mainly relied on. There is extreme tenderness marked by standing on one limb, or resting on the breast, and hence moping apart from the flock. When made to rise, the affected limb may be used to steady the body, or even to walk, with a limp, though in bad cases the sound limb only may be used. The affected joints are swollen, soft, hot, extremely tender, pitting on pressure, and later the seat of nodular yellow masses, usually hard, but sometimes fluctuating and in size from a pea to a hazel nut. The superimposed epidermis is thick, dry and scaly, falling off in flakes. At a more advanced stage the concretions may burst through the skin, discharging a buffy, granular, debris containing crystals of urates of ammonium or calcium, or of uric acid. Later still are ulcerous sores, involving the disintegrating urate nodules and the necrotic bones and cartilages. The deposits deflect the bones from their normal direction, causing not only nodular swellings on the toes but much crookedness and distortion. As in man the disease is essentially chronic and advances slowly, with anæmia, emaciation, debility and at times diarrhœa.
Diagnosis depends largely on the recognition of the excess of urates in the deposits. These appear under the microscope as fine acicular crystals, which in the harder portions have a concentric arrangement. A portion of the concretion may be moistened with a few drops of nitric acid and evaporated to dryness. To one part of the residue is added, by means of a pipette, a drop of aqua ammonia, and to another caustic soda. The ammonia develops a beautiful purple red color, and the soda a blue or purplish blue ring (Murexide test). In tubercular joints, which are common in birds, the caseated nodule is made up of cells and granular debris, with tubercle bacilli, and though cretaceous particles may be present they fail to give the microscopic and color appearances of uric acid.
Treatment. This must be largely preventive. The rich albuminoid feeding and close confinement must be modified especially in the older birds, and eliminating agents must be given in the drinking water. The Carlsbad combination (sodium sulphate 22; potassium sulphate 1; sodium chloride 9; sodium bicarbonate 18) may be used. Powdered colchicum ¼ gr. once or twice daily during an attack, or piperazin ½ gr. twice a day. Locally, abscesses should be opened, and like any sores or ulcers, treated with antiseptics (Salicylate of sodium 75 grs., glycerine 2 ozs.; or piperazin solution 2:100).