DIAGNOSIS 121 



due to syphilis. Whether we are to assume in these eases a gumma of the 

 brain (the simultaneous existence of destructive gummata of the skin in one 

 of these patients appears to favor this view), or whether we are to assume 

 a disturbance in the function of the kidney due to syphilis, is very difficult to 

 determine at present. The practically important point is this, that in the 

 course of syphilis, with or without cerebral symptoms, simple polyuria may 

 occur, and that antiluetic treatment in both instances may bring about a cure 

 of the diabetes insipidus. 



DIAGNOSIS 



The diagnosis of diabetes insipidus is usually easy; the important symp- 

 tom, polyuria, can be readily determined, care being taken not to confound 

 the disease with other conditions in which polyuria also occurs. Diabetes 

 mellitus may easily be excluded by an examination for sugar. The question 

 whether or not contracted kidney is present is not always so promptly solved. 

 Cases of chronic nephritis in which the urine is at times free from albumin 

 are not very rare; but the examination of the heart, and particularly the 

 hardness of the pulse, will generally lead to a correct diagnosis. It is note- 

 worthy that in diabetes insipidus, in spite of the fact that plethora serosa 

 occurs frequently, hypertrophy of the heart and changes in the tension of the 

 pulse never result. 



Difficulties in the exclusion of nephritis may, however, arise in an oppo- 

 site direction, namely, from the presence of slight quantities of alhumin in the 

 urine in diabetes insipidus. A number of clinical histories which describe 

 otherwise typical cases of diabetes insipidus, some of the hysterical type, con- 

 tain the statement that periodially small quantities of albumin could be 

 detected in the urine. It is difficult to exclude nephritis in these cases as they 

 have not come to autopsy; nevertheless the fact remains, that cases which in 

 their course and especially in their uniform benignity do not differ from the 

 ordinary picture of simple polyuria may from time to time show traces of 

 albumin in the urine. 



Amyloid kidney, less often than contracted kidney, may lead to confu- 

 sion; although occasionally albuminuria is absent here, the general condition, 

 the enlargement of the liver and spleen, make the diagnosis clear. 



Arteriosclerosis more often leads to diagnostic difficulties, as it tends 

 decidedly to increase the amount of the urine ; but here also the action of the 

 heart and pulse is conclusive. 



Chronic pyelitis must also be considered in the differential diaghosis ; in 

 some few cases of diabetes insipidus described in literature, one cannot help 

 suspecting that the writers were really portraying cases of pyelitis. The 

 reports that the urine always contained slight traces of albumin 'and a puru- 

 lent sediment are signiiicant. 



Finally, the possibility that diabetes insipidus may be mistaken for the 

 results of a simple increase of the intake of fluid must be considered. 



As a matter of fact this differentiation, at least for a time, may be simply 

 impossible; the limits vary and are partially arbitrary. If after simply dimin- 



