Again, a grave obstacle to the acceptance of Folin and Denis’ inference is that uricæmia, though incidental to nephritis, is not peculiar thereto.
Thus Roy Upham and Higley noted its presence in 85·6 per cent. of their cases of nephritis; but, on the other hand, they found that no less than 40 per cent. of another series of clinical cases, not suffering from nephritis, also showed uricæmia.
This would appear to indicate that, while uricæmia is an exceedingly common symptom of early chronic interstitial nephritis, it is by no means specific for that disorder; in other words, its diagnostic valency as a symptom of nephritis is distinctly limited.
Reverting now to gout, what evidence is there that the uricæmia therein is due to defective eliminatory capacity on the part of the kidney for uric acid? Certainly there is no proof that the kidney, at any rate in the initial stages of gout, suffers from this particular functional disability. Indeed, the fact that, at the very acme of an acute attack, the output of uric acid is not only not diminished, but actually increased, constitutes strong proof of the reverse.
Again, as modern investigations show, the variations in the uric acid content of the blood, re the incidence or intensity of attacks, are most erratic. Far from its being essential that uricæmia be present, acute attacks may occur with even a sub-normal uric acid blood content; in short, the variations are so erratic as to seem quite out of keeping with the assumption that the uricæmia in gout is primarily of renal origin.
If it were so, one would expect no such vagaries in the uric acid content of the blood. One would rather, given the existence ab initio of a renal functional defect, look for not only a permanent uricæmia, but further, from time to time, augmentations and diminutions thereof, synchronising with the rise and wane of gouty paroxysms; in other words, that in gout the clinical course and crises of the disorder would be linked up with harmonious variations in the degrees of uricæmia.
Uricæmia does not Necessarily Portend Gout
If it were so, why does not every case of nephritis develop gout? The researches of Myers and Fine have shown that uric acid is the nitrogenous metabolite that first accumulates in the blood in early interstitial nephritis. Only in its later stages do urea and other waste nitrogenous products undergo like retention therein.
Now let us review these findings, re nephritis, in light of another statement by Folin and Denis, which runs as follows:—
“In pure gout, unaccompanied by any abnormal urea retention in the blood, the kidney is damaged (so far as we yet know) only with its function of removing down to the normal level the uric acid of the blood.”