SUPPURATIVE NEPHRITIS

Under this heading will be considered all the processes generally classed under the heads of exudative pyelitis, pyonephrosis, and suppuration of the kidney. Tuberculosis, although coming properly under this head, will, because of its importance, be considered separately. This plan has been adopted for the reason that, clinically, the conditions are practically similar, the various changes that occur being often but different stages of the same general process.

Suppurative inflammation of the kidney may be brought about by four different methods of inoculation: first, by ascending infection from the lower urinary tract; second, by embolic infarction, as in general septicemia; third, by infection taking place in the course of what may be regarded as the normal excretion of bacteria by the urinary tract; and fourth, by the extension of suppurative processes into the kidney from without. Suppuration in the kidney may be localized in any portion of the organ, or it may be diffuse, the former condition being the more common.

In a large series of postmortems the writers found ascending infection to be by far the most frequent cause of suppuration. It may arise in any condition or disease in which infection of the lower portion of the urinary tract has taken place, as, for example, in the exudative urethritis of gonorrhea; in cystitis or suppurative disease of the ureters, and, finally, in pyelitis. As a rule, the infection travels upward from the urethra, prostate, or bladder, infecting the various portions of the excretory canal as it advances.

The mere presence of bacteria, regardless of the variety of organisms, in any of these portions of the urinary tract is not sufficient in itself to set up the process. Another and probably a more important factor, that of predisposition, must also be present. Thus pathogenic bacteria are often found in the urine under physiologic conditions, and, as a matter of fact, bacteria are often excreted by the urine in both pathologic and physiologic states without producing any local disease. This is particularly shown in regard to the colon bacillus, which is not uncommonly found in the urine, especially in constipation and in certain intestinal fermentations. Two such cases recently came under the care of the writers. In each case purgation caused a temporary disappearance of the colon bacillus from the urine, which reappeared

later. It is quite possible, as asserted by Nichols, of Montreal, that organisms so excreted may occasionally set up nephritis.

W. H. Thomson' has recently reported a series of cases in which colon infection of the kidney set up a diffuse nephritis manifested by the urinary findings of an active acute parenchymatous nephritis, but with symptoms of much less degree. Colon bacilli

Fig. 64.-Double pyonephrosis (one-third natural size). Originating from a primary cystitis and showing thickening of bladder wall, dilatation of both ureters, and extensive necrosis of renal tissue. Left kidney not opened. From a specimen in the museum of Carnegie Laboratory.

are found in abundance in the urine of these cases, which, not. withstanding their very serious appearance, Thomson finds recovery quite promptly under medication with urinary disinfectants, notably urotropin. A case under the observation of one of us seems to bear out Thomson's statements.

The most frequent factor predisposing in the development 1 "New York Medical Record," March 21, 1908.

of suppurative nephritis is hydronephrosis. This may be induced by any cause whatever, as when abnormal retention occurs, as in alcoholic stupor or other comatose conditions, in obstruction to the urinary passages, as from impaction of a calculus, in enlarged prostate, urethral stricture, and the like. In all these conditions, when the urine is retained until abnormal distention of the bladder, ureters, and renal pelvis takes place, the integrity of the epithelial

Fig. 65-Diffuse type of exudative or suppurative nephritis occurring in a pneumococcus septicemia. Complete necrosis and replacement of tubules is shown in the field: a, Malpighian body; b, infiltrating leukocytes.

lining of these cavities becomes so much impaired that, if bacteria are present in the urine, the hydronephrosis is very prone to be converted into a pyonephrosis. Pyonephrosis may, however, be excited by a mechanic irritant; thus the excretion of highly irritating urine, the presence of renal calculi, or other similar conditions may act as factors in its production. From this it must not, however, be concluded that every case of pyelitis or

b

even of pyonephrosis leads to suppurative nephritis. Recent observations made with the aid of the cystoscope have demonstrated that these conditions frequently exist and undergo spontaneous cure, or are relieved by catheterization and flushing of the ureters and pelvis.

When extension into the body of the kidney takes place from these ascending infections, it occurs through the secretory tubes of the medulla. In these cases the pyramids may be soon transformed into abscess cavities that retain the pyramidal shape and are continuous with the distended pelvis of the kidney. This process may continue until the entire medulla of the kidney is involved or until the cortex itself has become gradually necrosed and the entire kidney transformed into an abscess cavity inclosed in the thickened capsule, which, in most cases, acts as a limiting membrane to the suppurative process. If drainage is good and if but one organ is involved, as is frequently the case, the process may gradually be checked and very slight constitutional disturbance may result. The condition may often be unsuspected until a urinary examination is made, which will reveal the constant presence of pus in abundant quantities. It is remarkable, however, to what a limited degree urinary excretion is hampered, even when both kidneys are involved; in these cases uremia is very rare, and a double pyonephrosis has been known to exist for years without interfering with the business activity and often with but little inconvenience to the patient. Apparently, such a result is dependent on the amount of drainage and, to a certain extent, on the bacterial character of the inflammation.

Embolic infarction of the kidney is rather frequent, owing to the numerous terminal arterioles that are given off to the cortical portions of the kidney, and which are particularly prone to be the seat of emboli. Embolic infarctions occur most frequently in pyemia or in septicemia. In most cases the infarct precedes suppuration, the latter process being, however, greatly favored by the necrotic material present in the obstructed area. In a considerable number of cases, particularly in malignant endocarditis and puerperal sepsis, suppuration seems to occur independently of the existence of an infarct.

Suppurative nephritis due to the presence of emboli often runs a very mild course. Not infrequently these localized abscesses of the

kidney become encapsulated and give rise to but slight if any clinical manifestation; ordinarily, unless the abscess is very large, or if, as is unlikely, suppuration spreads, pyuria is absent. In short, abscess formation in the kidney does not display so marked a tendency toward extension or destruction of tissue as is the case with similar processes elsewhere. In a few cases these cavities may drain through one of the large tubules; when this occurs, pus may be found in small quantities in the urine. As a rule, however, in the writers' experience, the condition commonly goes unsuspected, except in a small number of cases in which the abscess is sufficiently large to present a palpable tumor or severe pain is

present.

Infection due to the presence of pathogenic organisms in the urine is not commonly mentioned as a cause of suppuration, but it is, nevertheless, one of the possible factors in its production. In constipation, in general septic conditions, in infective icterus, and in many other pathologic states bacteria are expelled from the body with the urine. Ordinarily, this takes place without serious consequences to the kidney, but instances undoubtedly occur in which bacteria are brought to the organ, and probably because of some mechanic state or a lowered resistance of the renal tissue, an inflammatory process is set up. Thus areas of suppuration are occasionally found in the kidney when no general sepsis has existed and when ascending infection may, with reasonable certainty, be excluded. Such cases usually follow the same course as embolic infarction, although occasionally, as in Weil's disease, diffuse suppurative nephritis may arise.

Suppurative nephritis originating from extension of the process into the kidney from outside sources is somewhat uncommon, except as a sequel to traumatism of the kidney; it is quite rare even in cases of perinephritic suppuration. Occurring under these conditions it resembles perinephritic abscess, and is perhaps best described under that head.

Perinephritic suppuration may arise as the result of rupture of a renal abscess into the perinephritic tissues, or as an extension of a diffuse suppuration of the kidney into this tissue. These are among the more infrequent causes, although rupture of a pelvic abscess, particularly when pelvic calculi are present, is relatively frequent. Most commonly it follows injuries received in this