PRACTICAL CONSIDERATIONS : THE KIDNEYS. 1887 



tissue of their walls. In continuation the nerve-fibres pass between the uriniferous 

 tubules and form plexuses surrounding the membrana propria. Smirnow traced 

 the ultimate fibrillae within the tubules, their free endings lying between the epithelial 

 cells. The vessels and tubules of the medulla are provided with similar but less 

 closely disposed nervous filaments which are destined chiefly for the muscular tissue. 

 According to the last-named investigator, the nerves of the kidney include some 

 sensory and both medullated and non-medullated fibres. The fibrous capsule also 

 possesses a rich nervous supply. 



Variations. — More or less conspicuous furrows are frequently seen on the surface of the 

 adult kidney ; these represent a persistence of the lobulation normally present in the foetus and 

 the young child. 



In addition to variations in size, a marked deficiency on one side being usually compensated 

 by a large organ on the other, the kidneys often present different degrees of union depending 

 upon abnormal approximation or fusion of the primary renal anlages. The connection may 

 consist of a band, chieffy of fibrous tissue, that unites otherwise normal organs ; or it may be 

 formed by an isthmus of renal tissue that extends between the approximated lower poles ; or 

 the two organs may form one continuous U "Shaped mass across the spine, then constituting a 

 "horseshoe" kidney. E.xtreme displacement and fusion may produce a single irregular organ 

 whose primary double anlage is indicated by the presence of two renal ducts that descend on 

 different sides of the pelvis to terminate normally in the bladder. Absence of one kidney 

 occasionally occurs, the organ present usually being correspondingly enlarged. Complete absence 

 of both kidneys has been observed as a rare congenital malformation. 



PRACTICAL CONSIDERATIONS : THE KIDNEYS. 



Congenital abnormalities of the kidneys may affect (a) their shape, size, and 

 number ; (d) their position ; and kidneys that are abnormal in one of these respects 

 are apt to be so in others. The matter is of practical importance in relation to the 

 diagnosis of intra-abdominal swellings and to the many operations now undertaken 

 for the relief of various renal conditions. 



(a) Anomalies as to Shape, Size, or Number. — One kidney may be congenitally 

 absent or greatly atrophied ; may be constricted so as to assume an hour-glass 

 shape ; or lobulated, as in the foetal condition ; or the two kidneys may be fused so 

 that ( I ) their inferior portions are united by a band of tissue — glandular or fibrous — 

 that crosses the vertebral column, usually in the lumbar region ( ' ' horseshoe 

 kidney") ; or (2) they may form an irregularly bilobed mass, one side of which is 

 much larger than the other, or become one single " disk-like" kidney lying in the 

 mid-line on the lumbar spine, on the sacral promontory, or in the hollow of the sacrum 

 (Rokitansky, Morris). 



Of these conditions the rarest is the true congenital absence, or extreme atrophy 

 of a kidney ( i in 2650) ; horseshoe kidneys are more than twice as common ( i in 

 1000) ; while one-sided renal atrophy associated with post-natal disease is relatively 

 frequent (i in 138) (Morris). 



Both kidneys have been absent in many still-born children and acephalous 

 monsters. In a very few cases a supernumerary kidney has been found. 



Anomalies affecting the blood-supply to the kidney occur in nearly 50 per cent, 

 of cases. The renal arteries are usually increased in number, or divide at once — 

 before reaching the hilum — into several branches, foetal conditions in the human 

 species that are permanent in many birds and reptiles. Accessory or supernumerary 

 veins are much more rarely found. 



{b) Anomalies of Position. — Congenital displacement — apart from the horseshoe 

 kidney — usually affects one kidney, which is apt to be found in the vicinity of the 

 sacral promontory or the sacro-iliac joint, but may be either higher or lower, and 

 may, by its malposition, give rise to serious or even fatal error in'diagnosis or treat- 

 ment. 



It would seem proper to include here those rare temporary displacements that 

 are due to the congenital presence of a mesonephron, which — as the usual support 

 given by the peritoneum is lacking, and as the contained blood-vessels are in such 

 cases of abnormal length — permits mobility of the kidney beyond the physiological 

 limits (floating kidney). 



