472 PHYSIOLOGICAL CHEMISTRY 



Collect the urine punctually at the end of every two-hour period until 8 

 P.M. and place in separate bottles. Collect the night urine from 8 P.M. to 

 8 A.M. of the following day in another bottle. Measure the volume of each 

 specimen of urine and determine in each case the specific gravity, total nitrogen, 

 and total chlorides. 



Interpretation. 1 The test is of particular value apparently as 

 giving earlier indications of diminished kidney efficiency than is true 

 of other tests used. It is sometimes difficult to interpret the results 

 obtained in terms of renal involvement because of the influence of 

 possible extrarenal factors. 2 In general, however, the normal response 

 is one in which the specific gravity figures vary 10 points or more from 

 the highest to the lowest and the volume of the night urine is 750 c.c. 

 or less. If the percentage of nitrogen and sodium chloride in the night 

 urine or in the highest of any of the day specimens is i per cent a 

 normal condition is indicated. Values under i per cent, however, 

 may or may not be abnormal. 



When kidney function becomes involved the first signs are usually 

 demonstrated in the night urine. The quantity becomes increased and 

 the specific gravity and the nitrogen concentration are lowered. One or 

 all of these changes from the normal may occur. In severe cases of 

 chronic nephritis an advanced degree of functional inadequacy of the 

 kidney is indicated by a markedly fixed and low specific gravity ; a 

 diminished output of both salt and nitrogen, a tendency to total poly- 

 uria and a night urine showing an increased volume, low specific gravity, 

 and low concentration of nitrogen. Such functional pictures are, 

 however, not confined to nephritis. They are found frequently in 

 many other conditions: pyelitis, cystitis, hypertrophied prostate, 

 marked anemia, pyelonephritis, polycystic kidney, and diabetes in- 

 sipidus. The following table taken from Mosenthal shows the response 

 of a normal individual: 



1 Kahn: loc. cit.\ Mosenthal: Arch. Int. Med., 22, 770, 1918. 

 2 Lyle and Sharlit: Arch. Int. Med., 21, 366, 1918. 

 Mosenthal and Lewis: Jour. Am. Med. Ass'n., 67, 933, 1916. 



