ABSTRACT
The kidney is a complex organ that is responsive to the changes in the whole organism. As such, kidney function is affected by various hormones, food intake and diet, shifts in acid–base status, and changes in blood pressure and fluid volume. Aldosterone is the major mineralocorticoid hormone secreted by the adrenal cortex. In the kidney, aldosterone promotes retention of sodium and bicarbonate, excretion of potassium and hydrogen ions, and secondary retention of water. Routine urinalysis is an essential part of the laboratory evaluation, and the results should be interpreted along with the results of a chemistry panel. Ideally, urine should be collected at the same time, or as close as possible to the time of blood collection for hematology and clinical chemistry. The ability of the kidney to concentrate urine above that of the glomerular filtrate is primarily a function of the loop of Henle and the distal tubule.
