1026 Hydroneplirosis. 



kidneys atrophies, until finally even the cortex becomes 

 atrophic; with this the process is arrested because no more 

 urine is secreted. If the impediment is proximal to the bladder, 

 only one kidney is usually affected; other impediments to the 

 outflow of urine necessarily lead to bilateral hydronephrosis. 



It is evideot that only chronic or periodical abnormal conditions of the 

 organs which discharge the urine are capable of producing hydronephrosis, since 

 its development requires a period of several months. Total occlusion of both 

 ureters or of the urine-carrying organs from the openings of the ureters down 

 is not followed by hydronephrosis because the animal perishes of uremia or of 

 rupture of the bladder in a comparatively short time. But even a unilateral total 

 occlusion of the ureter does not produce hydronephrosis if it is permanent, becaufe 

 then the pressure in the urinary passages rapidly increases, and therefore the 

 secretion of urine in the corresponding kidney diminishes just as rapidly and to 

 complete cessation (Senator). 



As to the individual causes, this much is certain that the 

 following atfections are, although comparatively rarely, of 

 fairly equal importance in all animal species; inflammation of 

 the bladder or of the ureters, obstruction of the ureters by 

 stones, secretions, coagulated blood (for instance in bacterial 

 pyelonephritis), the obliteration of the ureter-opening into the 

 bladder (evidently congenital [Kitt]), congenital valvular for- 

 mations, constriction of the ureter l3y muscular fibers of the 

 wall of the bladder (Lucks), stenosis of the urethra in enlarge- 

 ment of the prostate, compression through tumors, etc. 



The most frequent causes are, however, of different 

 character. In hogs. Lucks proved by the results of careful 

 examinations in 30 cases that the cause of hydronephrosis 

 usually lies in the fact that the openings of the ureters are 

 congenitally placed too low in the neck of the bladder (on one 

 or both sides) and that in the hog the attachment of the bladder 

 is very loose. This makes it possible that the partially filled 

 bladder, which then falls lower down, presses its neck, together 

 with the caudal portion of the ureter against the anterior border 

 of the pubis and thus periodically prevents the voiding of the 

 urine. In cattle other causes are probably active, for instance, 

 the occasional bending of the left ureter by the filled rumen, 

 in w^hich case the left kidney is pushed out of place (Breuer), 

 also the compression of the ureter by the filled stomach. 



In chronic inflammatory processes in the kidneys some urinary tubuli are 

 at times constricted in portions by the contraction of the connective tissue which 

 is undergoing atrophy, or are filled with small stones or cell masses, so that the 

 canals which are attached to the Malpighian bodies are dilated, the urine con- 

 tinuing to be secreted, and are thus transformed into retention cysts. Such small 

 cysts are sometimes found in large numbers, the contiguous ones become confluent 

 and the entire kidney is transformed into a collection of cysts of variable si^es 

 (cystic kidney, hydrops cysticus). In this form the trouble is found especially 

 in cattle, and occasionally as a congenital condition. 



Anatomical Changes. The dropsical alteration of the 

 kidney may be met with in various stages. If the process is 

 far advanced, the kidney is changed into a large undulating 



