CHAPTER IX. 



THE URINARY ORGANS. 

 The Kidneys. 



Malformations. 



BOTH kidneys may be absent in connection with extensive malformation in foetuses 

 which are not viable. 



Absence of one kidney is not uncommon, the left kidney being more frequently 

 absent than the right. The absence of the kidney may be complete, the ureter being 

 also absent; there may be an irregular mass of much-atrophied kidney tissue with con- 

 nective tissue and fat, or there may be only a little mass of connective tissue and fat 

 representing the kidney, and a ureter running down to the bladder. The single kidney 

 Avhich is present is usually much enlarged. It may be in its natural position or dis- 

 placed downward. When both kidneys are present one of them may be much larger 

 than the other. One kidney may have two pelves or two ureters. 



FIG. 376. HORSESHOE KIDNEY. 



A frequent malformation is the so-called horseshoe kidney (Fig. 376). The lower 

 ends of the kidneys are joined together by a commissure. The commissure is usually 

 composed of kidney tissue, but sometimes of connective tissue. The two kidneys may 

 be normal, except for the commissure; or their shape, the arrangement of the vessels 

 and ureters, and the position may be unnatural. The two kidneys may be united 

 throughout so as to look like a single misshapen kidney with two or more pelves and 



