URINARY CONCRETIONS 463 



not infrequently. Occasionally these arc soft and chalky, hut if well crystallized, 

 they are the liartlost of concretions. 



Cystine calculi'- are rare but very interesting formations. Cystine 

 S-CH(N1I...)-C()()1I 



I is important as the sulphur-containing portion of the protein 



S-CII(NH2)-C()0II 



molecule. Under normal conditions all the cystine taken in food is completely oxi- 

 dized and none (or uncertain traces) appears in the urine. In certain individuals 

 the urine contains considerable quantities of cystine constantly {cyslinuria, see 

 Chap xxi), and occasionally in these cases soft concretions of nearly pure cystine 

 are formed in the urinary passages. Cystine calculi may reach the size of a hen's 

 egg, are crystalhne in structure, and in the urine of such patients the characteristic 

 hexagonal crystals may usually be found. The cystine of calculi is identical with 

 that from proteins and may be associated with tyrosine.'^ 



Xanthine Calculi — Xanthine is the most abundant of the purine bases normally 

 present in urine, but the total amount is extremely small. Like uric acid, it fluc- 

 tuates in amount according to the amount of destruction of nucleoproteins, either 

 of the food or of the tissues. Concretions consisting chiefly of xanthine, which is 

 often mixed with uric acid, are extremely rare, but a few isolated specimens having 

 been described. Rosenbloom could collect but six cases in the literature, adding 

 one himself.'* 



Indigo calculi, derived from the indican of the urine through oxidation, have 

 also been described a few times. 



Urostealith calculi, composed of fatty matter, have been occasionally observed. 

 Although some of the concretions described under this head have really repre- 

 sented foreign bodies introduced through the urethra (e. g., Kruckenberg's concre- 

 tion of paraffin from a bougie), yet true fat concretions do occur. The origin of the 

 fat in these stealiths is unknown; possibly it comes from degenerated epithelium. 

 Horbaczewski'5 analyzed such a specimen which had the following percentage 

 composition: 



Water 2.5 



Inorganic matter 0.8 



Organic matter (chiefly protein) 11.7 



Fatty acids 51.5 



Neutral fat 33 . 5 



Cholesterol traces 



The fatty acids consisted of stearic, palmitic, and probably myristic acid. 



Cholesterol calculi have been found in the urinary bladder in a few instances, 

 the cause being unknown. Horbaczewski^* describes one weighing 25.4 grams, 

 found in a patient who had previously had cystine calculi; it contained 95.87 per 

 cent, of cholesterol and but 0.55 per cent, of inorganic material. Gall-stones have 

 been known to enter the urinary bladder through a fistula between the gall-bladder 

 and urinary bladder. ^^ 



Fibrin "calculi," formed from blood-clots, often more or less impregnated with 

 urinary salts, have occasionally been observed. Other proteins may also form simi- 

 lar calculi.'" 



General Properties of Urinary Concretions.'^ — The hardness 

 depends partly upon the chemical composition of the calculus, but 

 more upon the rate and condition of formation (Rowlands, Kahn). 



1- Literature concerning cystine, see Friedmann, Ergeb. der Physiol., 1902 (i), 

 15; Marriott and Wolf, Am. Jour. Med. Sci., 1906 (131), 197. 



13 Abderhalden, Zeit. physiol. Chem., 1907 (51), 391; 1919 (10-1), 129. 



» N. Y. Med. Jour., Jan. 16, 1915. 



's Zeit. physiol. Chem., 1894 (18), 335. 



16 See Finsterer, Deut. Zeit. klin. Chir., 1906 (80), 426. 



1^ See Morawitz and Adrian, Mitt. Grenz. Med. u. Chir., 1907 (17), 579. 



1* Systems for procedure in determining the nature of urinary calculi are given 

 by Hammarsten (Text-book of Phj'siol. Chem.) and by Smith (Reference Hand-book 

 of Med. Sci.). 



