Is it not clear, then, that in the early stages of nephritis, viz., prior to retention of urea and other waste nitrogen, we have precisely that isolated functional renal disability, i.e., inability to excrete uric acid, that we postulate to be in operation in the initial stages of gout?
Yet, notwithstanding this similitude in the blood content of the two disorders, cases of nephritis do not necessarily develop gout. Indeed, as a matter of fact, examples of nephritis, of all grades and intensities, may run to their full end without manifesting any symptoms even remotely reminiscent of gout. Even Magnus Levy, ardent advocate as he is of the primary renal origin of gout, could not but admit that this salient clinical obstacle barred the way to acceptance of his otherwise plausible view. However, he fails to proffer any other solution of the problem.
To our mind, albeit, the disparity carries with it the inevitable postulate that in gout some other factor intrudes, some tertium quid, something vital, something biological, haply an infection. For even if we grant, for the sake of argument, that renal retention, if it were proved, might explain such anomalies in the excretion of uric acid and other nitrogenous metabolites as occur in gout, yet, nevertheless, no one could possibly contend that this factor alone could explain the nature of gout, could adequately account for its dramatic and protean phenomena.
To what may be Ascribed the Deficient Eliminating Capacity of the Kidney for Uric Acid?
Naturally the advocates of the renal theory had to account in some way for the alleged functional disability of the kidney. Thus, Sir Dyce Duckworth, recalling the occasional occurrence in hysteria of anuria, held that, judging from the general phenomena of acute gout, “the influence of the nervous system ... must not be left out of account as a possible determining factor for renal inadequacy.”
Others, with whom Duckworth disagreed, propounded the view that the deposition of urates in the renal tissues was essential for the initiation of a nephritis in the gouty. Duckworth, on the other hand, held that nephritis could develop in their absence.
Croftan considers the renal changes in gout identical with those of chronic plumbism. From experiments with hypodermic injections of xanthine and hypoxanthine over a prolonged period, he concludes that the presence of minute quantities of purin bases in the circulation is capable of producing marked renal changes. On the other hand, uric acid, injected into the circulation of healthy animals for a period of over three months, produced no renal change whatever.
As to this possibility, viz., that the circulating uric acid might lead to nephritis in the gouty, some reflections of Folin and Denis are instructive. Normal blood, according to these observers, contains not less than from 1-2 or 2-5 mg. per 100 grams, while that of gouty blood does not, in their experience, exceed 6 mg. Continuing, they observe, “There is, however, no reason to suppose that a uric acid concentration of 4-6 mg. per 100 grams of blood is very much more irritating or stimulating to the kidney than the somewhat more dilute solution represented by normal blood. Disregarding the insolubility of uric acid, the elevation of its threshold of elimination from 2-4 or 6 mg. (per 100 grams of blood) is certainly a small one. Kidneys in which the threshold of elimination for urea has risen by 10-20 mg. (per 100 grams), or even more, are extraordinarily common.”
While they consider that such urea and total nitrogen retention may possibly bespeak latent or incipient nephritis, they recognise that no appreciable effects on health have as yet been determined in connection therewith. But more pertinently to our point, they make the further pregnant observation, “In the case of uric acid it seems to be purely a matter of insolubility that corresponding or even smaller degrees of kidney insufficiency with slight uric acid accumulation should result in all the serious consequences involved in the development of gout”!
Again, some have attempted to account for the assumed renal incapacity as being part of the tissue peculiarity of the gouty subject. “Without doubt,” says Duckworth, “there are peculiarities of tissue in the gouty, and with this may very possibly be associated peculiarities of tissue function and metabolism.”