DIABETES INSIPIDUS 875 



chlorids should be attended by a corresponding increase in vater and a 

 relative diminution in other solids. Leschke(c) (d) points out the well 

 known fact that normal kidneys, when water is withdrawn, can concentrate 

 urine to a very high degree, whereas in diabetes insipidus the specific 

 gravity rarely reaches 1.010. When insufficient water is given, symptoms 

 of uremia result, the freezing point of the blood serum falls and the con- 

 centration of urea and sodium chlorid in the blood may reach a very high 

 level. He ascribes thirst to a local stimulation of the cortex of the brain 

 by the increased amount of salt in the blood. 



Prognosis 



The outcome of any case of diabetes insipidus depends entirely upon 

 the nature of the causal lesion. Cases due to tumor are always serious. 

 Whether the course is long or short depends upon the malignity of the 

 growth. Where the syndrome is due to syphilis, the prognosis is relatively 

 not so serious. Much depends upon early and thorough antiluetic treat- 

 ment. Cases associated with brain injury are often very severe in char- 

 acter and of short duration. In those instances where the symptoms are 

 apparently due to a disturbed function of the hypophysis, the course is 

 light and transitory. This is usually the case in the polyurias of meno- 

 pause and pregnancy. In many cases, chiefly those of obscure origin, the 

 syndrome may persist for ten to twenty years or even longer. Age seems 

 to make no difference; children may live for years and adults may die 

 quickly, or the converse may be true. In some cases the polyuria dis- 

 appears to reappear again while other symptoms may persist and become 

 more aggravated. Death usually results for reasons which have nothing 

 to do with diabetes insipidus, being caused by some associated disease. 

 Where the illness has persisted for a long time, cachexia may be very pro- 

 nounced. As in many brain lesions, coma often precedes death. 



Diagnosis 



The recognition of the syndrome is comparatively easy. The cardinal 

 signs are severe polyuria, a sugar-free urine of low specific gravity, insati- 

 able thirst, dry skin, 'and weakness. The diagnosis is confirmed if these 

 are promptly relieved by the subcutaneous administration of pituitrin. 

 Disturbances of vision, sex gland development and function -may or may 

 not be present. With this evidence at hand, it may be assumed that there 

 is some lesion or functional disturbance in the brain area between the 

 optic chiasm and the inter peduncular fossa. The nature of this lesion 

 should be carefully investigated. In the absence of history of injury, 

 evidence of gumma, tuberculosis, or brain tumor should be sought. 



