Pathogenesis. 1015 



large, or by the full rumen or through some disease of the 

 urinary organs. The influence of predisposing factors may 

 indeed be so important, that without it the pyelonephritis 

 would not have developed in spite of the bacterial invasion 

 of the kidneys. 



Pathogenesis. In the ordinary hematogenic origin of 

 pyelonephritis the l)acteria are arrested in the capillaries of 

 some glomeruli in one, more frequently in both kidneys, and 

 not rarely already in the small arteries; they then produce 

 a local inflammation of the related portions of the cortex, or 

 a thrombosis. A considerable portion of the bacteria is 

 eliminated and is compressed into cap-shaped bunches in the 

 capsules of Bowman, and partly transported with the urine. 

 The experiments of Orth and J. Koch, and also the micro- 

 scopical examinations of Ernst have shown that the eliminated 

 bacteria accumulate and multiply in the collecting tubules in 

 the lower portions of the medullary portion, whereupon an 

 inflammatory process commences in the immediate vicinity, also 

 in the mucous membrane of the papilla, of the renal pelvis 

 and in the ductus papillaris. In certain cases the deleterious 

 action of the microorganisms which are wedged in the renal 

 capillaries appears to liecome manifest only after their elimina- 

 tion in the collective tul)ules. 



The further sequels of the inflanmiation differ to a certain 

 degree with the nature of tlie virus and according to the 

 presence or absence of a mixed infection. After the entrance 

 of the corynel)acillus renalis the more or less localized inflam- 

 mation results in necrosis which leads to the formation of small 

 softened foci in the kidney, while in the center of the papilla 

 a sequestrum is formed, surrounded by healthy or at least by 

 not degenerated tissue in which the collective tubules break 

 up into fibres. Eventually caseation and perhaps calcareous 

 incrustation of the necrotic tissue takes place and at the 

 periphery the inflammatory process either progresses or the 

 inflanunatory focus is circumscribed by a zone of demarcation. 

 If pyelonephritis has been produced by other microorganisms 

 the process differs only in so far as the inflamed tissue under- 

 goes softening and suppuration. The same is to be observed 

 in mixed infection which occurs frequentl}^ In the surround- 

 ings of the necrotic foci the connective tissue proliferates and 

 then atrophies while the unaffected portions of the kidneys 

 hypertrophy. 



Sooner or later an inflammation of the descending urinary 

 passages is added to the process in the kidney. Owing to 

 the constant contact of the mucous membrane of the renal 

 pelvis with the bacteria and inflammatory products which ac- 

 cumulate in the corners of the pelvis, the tips of the originally 

 affected papilla and of other papillae, as well as the mucous 



