As far as the frequency of renal disease is concerned, influenza does not occupy any particularly prominent position in comparison to other acute infectious diseases. The influenza bacteria and toxins are by no means so dangerous to the kidneys as, for instance, the toxins of scarlet fever, diphtheria, pneumonia, erysipelas, and smallpox.
All the statistics reveal an infrequency of acute nephritis, and this accords also with the reports of numerous experienced observers.
Von Leyden mentions in detail but one case which, on postmortem examination, was found to be a typical glomerulonephritis. Mosler, Strumpell, Drasche, and Pribram each report but one or two cases of acute hemorrhagic nephritis. Senator observed it "a few times."
In the German collective investigation only 4.5 per cent, of the observers mention the complication of "nephritis and albuminuria." The German army report mentions, among 55,263 patients, but 10 with "severe inflammation of the kidneys."
Anton (Wiirzburg) found nephritis in 2 per cent, and Gmeiner in 1 per cent, of the cases; Gutmann (Nuremberg) saw but four cases of "genuine acute nephritis" (1.5 per cent.) among 262 patients.
Among the 439 influenza patients in the pandemic, we saw "acute hemorrhagic nephritis" but twice. But even at that time we called attention in our influenza lectures to the fact that during the months after the termination of the epidemic remarkably many cases of nephritis were admitted, without any etiologic history other than an antecedent attack of influenza. Perhaps these were cases of a post influenzal nephritis analogous to those following scarlet fever, tonsillitis, and diphtheria.
Pathologic reports are naturally scanty (Wallis, Weichselbaum, Ribbert); they assign the nephritis partly to parenchymatous degeneration and partly to glomerular inflammation. Extensive necrotic processes were observed by Beneke and Kuskow; the latter also found numerous small purulent foci in the kidney, doubtlessly due to a secondary infection.
A transient, slight albuminuria, the so called "febrile" or congestive albuminuria, is observed when there are diffuse capillary bronchitis and cyanosis, with pneumonia as a complication, or large pleural effusions, and in cardiac weakness. Many believe that this transient albuminuria is also due to the influence of the toxins.
Manassein, Zdekauer, Hermann and Socoloff, Engel-Bey* emphasize the great frequency of albuminuria in influenza. Teissier claims to have seen it in one half of the cases, Grandes 23 times among 29 cases, and Senator 18 times among 52 cases-that is, in about one third of the cases. On the other hand, Anton could find a slight albuminuria in but 5 per cent, of the cases, and Krehl in 3.5 per cent. According to the Swedish physicians (collective investigation), albuminuria "but rarely and transiently" occurred. As the result of our own observations, we agree with the last mentioned authorities, who believe albuminuria in influenza to be of rare occurrence.
* Loc. ext., p. 47.
These diametrically opposed views regarding the frequency of albuminuria in influenza no doubt depend partly on the different methods employed for the detection of albumin.
Only serum albumin and serum globulin are of clinical significance -that is, in indicating renal mischief; albumose and nucleo albumin, on the other hand, are not interesting, as these bodies in themselves may be. Fallacies may easily occur, as, for instance, in applying the boiling test with the addition of acetic acid (formation of soluble acid albumin) or by applying the cold nitric acid test (precipitation of nucleo albumin, which is mistaken for serum albumin). The ideal method for the clinical demonstration of albumin is not that which demonstrates the presence of any proteid body (serum albumin, serum globulin, albumose, nucleo albumin), but that which only shows serum albumin and serum globulin.
This is also the place to consider glycosuria and diabetes mellitus. The latter is frequently mentioned as a sequel of influenza (Rob. Saundby, Broadbent, Bouchard, Eichhorst, Rosenstein). Bossers quotes several cases from Dutch literature. A. Hennig claims to have observed diabetes frequently as a sequel of influenza. Fischl found transitory glycosuria often after the termination of the fever, and Frankhauser even states that he found sugar in the urine of all cases. Influenza may very likely have often caused the outbreak of a latent diabetes, and yet more frequently may a latent diabetes have become evident only from the fact that the attack of influenza led to an examination of the urine. [Schwarz saw glycosuria occur with post influenzal neuritis. Both symptoms improved together. Glycosuria may recur with a second attack of influenza and then persist.-Ed.]
The unfavorable influence of influenza upon an existing diabetes is emphasized by Kahler, Drasche and Fereol, and others. Especially dangerous to diabetics was diffuse capillary bronchitis or pneumonia.
Cystitis was observed occasionally after influenza, as after other acute infectious diseases. Cases of "retention of urine for several days" (Ehrenhaus, Bilhaut), of "vesical paralysis" (Swiss reports), of vesical spasm, cystodynia, enuresis nocturna, following influenza belong to the extensive domain of influenza neuroses.
Goldberg observed " complete and sudden recovery, after influenza, from a post gonorrheal cystitis that had existed for one and one half years." He thinks it possible that the influenza toxins eliminated in the urine may have exerted an inhibitory action upon the microbes of chronic cystitis. On the other hand, three patients of Trossat, with chronic catarrh of the bladder, had an acute attack as a consequence of the influenza.
As far as the chemic condition of the urine, apart from albuminuria, is concerned, there are but scanty and unimportant reports. No exact metabolic experiments were made during the influenza period. The rapid and important losses in weight mentioned above (p. 667), even in uncomplicated cases of influenza, point to deep seated metabolic disturbances.
The reports about the quantity of urine, its specific gravity, uric acid and urea ehmination, acidity, and the increase in phosphates, emphasized by many authors (Huchard, on the contrary, found them decreased), contain nothing worthy of detailed mention here. There is nothing unusual in the fact that, in a disease like influenza, which is frequently accompanied by high fever and profuse sweating, the quantity of urine may be so decreased that anuria lasting from twelve to sixteen hours may occasionally occur (Alison). Baumler found uro bilinuria in many cases, Alison frequently, and Hayem in all cases; Hayem considers this symptom characteristic of influenza. The tests for the detection of urobilin are now so delicate that urobilin can often be demonstrated in the urine of healthy individuals.