Adaptive processes in a single kidney after nephrectomy are manifested in the early stages of compensatory hypertrophy of the remaining kidney. Changes in kidney size (length, width, thickness) were determined. The results of studies have shown that the width of the kidney, not length, is a predictor of renal failure. Renal volume has been shown to be the optimal parameter for predicting renal function. Microscopic and submicroscopic changes of structural components of nephrons at different times after nephrectomy are described.