What Relation, if any, Exists between the Uric Acid Content of the Blood and Attacks of Gout?
If uric acid be causally related to gout, it would seem reasonable to expect that the blood content thereof would stand in some clear relation to the incidence or intensity of attacks.
But, according to Pratt and others, no variations indicative of such a relationship obtain. For, independently of acute attacks, and, moreover, in the absence of any pronounced renal inadequacy, the blood of gouty subjects, even on a purin-free diet, contains, as a rule, 4-9 mg. of uric acid.
More pertinently to our point, in the experience of Daniels and McCrudden, it transpires that, contrary to the usually accepted teaching, typical acute attacks might occur without any variation in the uric acid content of the blood or its excretion.
Nor did their iconoclastic findings cease here, for, mirabile dictu! attacks ensued even when the uric acid blood content was at a sub-normal level; this latter, owing to the victims being at the time on atophan, which increases uric acid elimination. In this connection it is worthy of note that, according to Pratt, the uric acid content of the blood may at times be low, even when atophan has not been taken. In one of his cases, on a purin-free diet, only 1·7 mg. was present, and in another case, on a mixed diet, 1·9 mg.
Daniels and McCrudden, too, note that the uric acid content of the blood in gouty subjects may be persistently lowered, even under the normal average. His, again, has recorded an instance of a gouty subject, with multiple tophi, whose blood did not contain an excess of uric acid. Bloch, also, took 200 c.c. of blood from a man, aged twenty-five, suffering at the time from a typical attack of gout in the big toe; but uricæmia was not present.
Bass and Herzberg injected uric acid into the blood of gouty subjects until its content thereof reached 10 mg. per 100 c.c., this without any joint symptoms supervening. The same observers, aspirating joint fluids in non-gouty subjects, noted that the uric acid content was approximately the same as that of the blood. But, in contradistinction thereto, in two gouty subjects, victims of uræmia, they found in the joint fluids 18·5 and 20·8 mg. of uric acid, while the blood content was only 10 mg. and 8·2 mg.
Furthermore, intravenous injection of uric acid engendered a lesser degree of uricæmia in the gouty—this despite impaired renal excretion. To their mind, therefore, the inference was that the bodily tissues in gout display an enhanced capacity for taking up uric acid.
Lastly, Walker Hall, discussing the question as to whether any relation obtains between the degree of uricæmia and the onset of acute attacks, observes that, “the evidence is more general than specific.” Thus he reminds us that excessive intake of purin food has sometimes been followed by, or associated with, an acute outbreak. Also, that the leucocytic destruction which occurs during acute lobar pneumonia and after the use of X-rays has occasionally coincided with an acute paroxysm. To this, again, must be added the fact that atophan curtails the duration of acute attacks, apparently by exciting an increased uric acid output. Superficially regarded, these facts might appear to be conclusive; but, as Walker Hall states, it must be recalled that overeating, overdrinking, trauma, mental disturbances, atmospheric vicissitudes, and bacterial infections have also preceded acute outbreaks.
To sum up, the main conclusions deducible from the foregoing clinical and experimental findings would appear to be that:—