1. In acute experimental hydronephrosis chloride retention occurs as well as retention of water, urea, and phenolsulfonephthalein.
2. If both water and chlorides are retained there may be no appreciable rise in the plasma chloride content.
3. When chlorides are retained, but not water, the chloride content of the plasma rises strikingly.
4. After the removal of the ureteral obstruction in acute hydronephrosis all renal functions, water, urea, and chloride excretion, may be rapidly restored in equal degree, or the chlorides may be retained temporarily while there is free excretion of water and urea.
5. In chronic hydronephrosis adequate daily excretion of urea and chlorides may be maintained by a compensatory polyuria.
6. Chloride retention or an abnormal chloride excretion may occur in certain renal lesions when there is no change in the urea, phenolsulfonephthalein, or water excretion.