416 DISEASES OF THE URINARY ORGANS. 



dilatation of the pelvis and calices of the kidney, hydroneph- 

 rosis is the descriptive term (Fig. 192). 



Calculi not infrequently occur in the pelvis of the kidney, 

 sometimes attaining quite large dimensions; the term renal 

 gravel is applied to the smallest gritty particles. During 

 their formation the calculi often become more or less accu- 

 rately moulded to the shape of the pelvis and the calices. 

 They may be composed of uric acid, oxalate of lime, and 

 phosphates, and rarely of cystin and xanthin. The results 

 of their presence may be very serious. The smallest particles 

 may pass through the ureter from time to time and give rise 

 to attacks of excruciating pain renal colic; larger ones, by 

 obstructing the ureter and the outflow of urine, may cause 

 hydronephrosis. The continued irritation produced by a 

 large calculus results generally in a pyelitis, and in some cases 

 seems to be the exciting cause of cancer. 



URINARY BLADDER. 



Fissure of the bladder a congenital malformation is 

 rather common, occurring as the result of a failure of the 

 visceral arches to coalesce in front. The absence of the 

 anterior wall of the abdomen and bladder exposes to view, 

 protruding and filling the cleft, the inflamed mucous mem- 

 brane of the posterior wall of the bladder which has been 

 pushed forward by the abdominal viscera exstrophy. The 

 extent of such a fissure varies greatly. It may involve the 

 pubic bones, and in the female, the vagina, clitoris, and urethra; 

 or the bladder may be perfectly formed and the cleft confined, 

 in the male, to the urethra, constituting an epispadms. 



Hypertrophy of the muscle- walls of the bladder results 

 from some obstruction either of the neck of the bladder or of 

 the urethra as by enlargement of the middle lobe of the 

 prostate or a urethral stricture. 



The mucous membrane of the bladder is raised into trabec- 

 ulse by the bundles of hypertrophied, interlacing muscle- 

 fibres, giving rise to an appearance somewhat similar to the 

 inner surface of the ventricle of the heart. 



Inflammation of the bladder cystitis may be acute or 



