876 JOHN R. WILLIAMS 



Differential Diagnosis 



Diabetes insipidus is to be distinguished from a number of other dis- 

 eases which are characterized by polyuria. Chief among these may be 

 mentioned diabetes mellitus, functional neuroses as epilepsy and hysteria, 

 cardiovascular disease in which there may be cardiac hypertrophy, arterial 

 hypertension, and arteriosclerosis. Chronic kidney disease, including 

 pyelitis and amyloid kidney, may also simulate diabetes insipidus. Some 

 individuals from force of habit and those accustomed to drinking large 

 quantities of fluids as milk, beer, cider, and fruit juices, may void urine in 

 large amounts. 



As compared with cases of diabetes insipidus, the polyuria of hysteri- 

 cal and epileptic individuals develops more gradually and is much less 

 severe. The functional neurotic individual will have much less thirst and 

 the volume and specific gravity of the urine will be much more variable. 

 Only in borderline cases is one likely to confuse polyuria of the neuroses 

 with the syndrome of diabetes insipidus. 



In cardiovascular disease, thirst is a minor and usually absent symp- 

 tom. Frequent and increased night urination characterizes chronic 

 nephritis; in diabetes insipidus, the polyuria is constant both day and 

 night. Furthermore, the urine of the nephritic shows definite and char- 

 acteristic changes which are not observed in uncomplicated cases of dia- 

 betes insipidus; as for example, pus, renal cells, casts, and marked varia- 

 tions in specific gravity. The blood of the nephritic usually shows evidence 

 of nitrogen retention as increased urea, creatinin, and uric acid. Edema 

 due to chlorid retention may be present. In pure diabetes insipidus, 

 nitrogen retention and edema are not factors. The body of the cardio- 

 nephritic does not show the dystrophic changes which are so evident in 

 diabetes insipidus, as very dry skin with absence of perspiration, anhidro- 

 sis, and genital maldevelopment. Arterial hypertension and cardiac hy- 

 pertrophy are not a part of the symptom complex of diabetes insipidus. 



Diabetes mellitus is easily distinguished from the insipidus type by the 

 high specific gravity of the urine, glycosuria, increased blood sugar, and 

 frequently complicating acidosis. The distressing symptoms of diabetes 

 mellitus are promptly relieved by proper restriction of diet, but are 

 unaffected by pituitrin administration. Diabetes insipidus cannot be 

 alleviated by diet but is benefited by pituitrin. 



Cases of combined diabetes mellitus and insipidus and reports in which 

 the former type has changed to the latter or conversely have from time to 

 time been published. It cannot be assumed that true diabetes mellitus is 

 present unless there is a definite hyperglycemia which bears a more or 

 less direct relation to food intake. Cases of diabetes insipidus which from 

 time to time show traces of urine sugar are more likely to be of the renal 



