CHAPTER XXI. 



URINE: CALCULI. 



URINARY calculi, also called concretions, or concrements are solid 

 masses of urinary sediment formed in some part of the urinary 

 tract. They vary in shape and size according to their location, the 

 smaller calculi termed sand or gravel in general arising from the 

 kidney or the pelvic portion of the kidney, whereas the large calculi 

 are ordinarily formed in the bladder. There are two general 

 classes of calculi as regards composition, i. e. } simple and compound. 

 The simple form is made up of but a single constituent whereas the 

 compound type contains two or more individual constituents. The 

 structural plan of most calculi consists of an arrangement of con- 

 centric rings about a central nucleus, the number of rings frequently 

 being dependent upon the number of individual constituents which 

 enter into the structure of the calculus. In case two or more cal- 

 culi unite to form a single calculus the resultant body will obviously 

 contain as many nuclei as there were individual calculi concerned 

 in its construction. Under certain conditions the growth of a cal- 

 culus will be principally in only one direction, thus preventing the 

 nucleus from maintaining a central location. The qualitative com- 

 position of urinary calculi is dependent, in great part, upon the re- 

 action of the urine e. g., if the reaction of the urine is acid the 

 calculi present will be composed, in great part at least, of substances 

 that are capable of depositing in acid urine. 



According to Ultzmann, out of 545 cases of urinary calculus, 

 uric acid and urates formed the nucleus in about 81 per cent of the 

 cases; earthy phosphates in about 9 per cent; calcium oxalate in 

 about 6 per cent ; cystine in something over i per cent, while in about 

 3 per cent of the cases some foreign body comprised the nucleus. 



In the chemical examination of urinary calculi the most valuable 

 data are obtained by subjecting each of the concentric layers of the 

 calculus to a separate analysis. Material for examination may be 

 conveniently obtained by sawing the calculus carefully through the 

 nucleus, then separating the various layers or by scraping off from 

 each layer (without separating the layers) enough powder to con- 

 duct the examination as outlined in the scheme (see page 364). 



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