456 CALCIFICATION, COXCKETIO\>S, AXD IXCRU^TATIONS 



as furnishing the primary nucleus of calculi of preponderatingly cal- 

 careous or mixed composition. Apparently there are marked differ- 

 ences in the prevailing composition of calculi in different countries ; in 

 China, for example, Pfister "'^ found eleven of twelve calculi composed 

 of uric acid. 



Uric acid is eliminated combined chiefly with sodium, potassium^ 

 and ammonium ; according to some authors, as a biurate, according to 

 others, as a quadriurate. If the urine is excessively acid, it con- 

 tains much acid phosphates, which withdraw part of the bases from 

 the uric acid, and this, when free, crystallizes out if in excess. Hence 

 tlie foruuition of uric-acid concretions is favored by high acidity of 

 the urine, by concentration of the urine, or by an increased elimina- 

 tion of the uric acid. The last may result from excessive nuclein- 

 rich food, or from excessive catabolism of the tissue nucleoproteins 

 (e. g., leucocytosis from inflammatory diseases or leukemia), which 

 conditions are also usually associated with an increased urinary acid- 

 ity. (The chemistry of uric acid is discussed more fully in the chap- 

 ter on ''Gout," Chap, xxi.) 



Uric-acid calculi are formed chiefly in the pelvis of the kidney, but 

 many pass into the bladder. They are quite hard, and yellow or 

 reddish-yellow in color, because of the presence of vrochrome and 

 K'rohilin, the former of which seems to be chemically combined and 

 the latter but physically, since it can be washed out with v/ater. 

 Uraerythrin or uromelanin (a decomposition product of urochrome) 

 may also be present. Not infrequently calcium oxalate is present, 

 sometimes in considerable quantities. Other urinary constituents may 

 be present in small amounts. In case the calculus enters the urinary 

 bladder it may set up irritation leading to infection; the urine then 

 becoming alkaline, calcium and ammonio-magnesium phosphate will 

 be deposited upon the surface, and the uric acid will be more or 

 less dissolved out and replaced by the phosphates (metamorpho- 

 sis). 



Urate calculi occur chiefly in new-born or young infants, and rarely 

 in adults. In the young thoy are related to, and may originate in, 

 the deposits of urates in the pyramids of the kidney (tlie so-called 

 urate or uric-acid "infarcts"), which have been supposed to result 

 from the decomposition of the nucleoproteins of the nucleated fetal 

 red corpuscles. (See "Uric Acid," Chap, xxi.) The concretions are 

 composed chiefly of either ammonium or sodium urate, but potassium 

 and even calcium and magnesium urate may be admixed. Their 

 genesis in the young probably depends upon injury to epithelium by 

 the excessive urates of tlie "infarcts," whicli affords a suitable 

 nucleus for their start; their growth depends chiefly upon the con- 

 centration of the infant's urine. In adults they may arise secondary 

 to an ammoniacal decomposition of the urine. Urate concretions are 



73aZeit. Urol., 1M13 (7), 945. 



