Introduction: history and problems of compensatory adaptation of renal functions and of compensatory hypertrophy of the kidney.

The history of observations and experimental work on compensatory changes following the loss of renal mass, and the historical reasons for the distinction between the concepts of compensatory adaptation (of renal functions) and of compensatory hypertrophy (of nephrons) are outlined. While the effector mechanisms of both types of compensatory changes are being elucidated at a rapid pace, many questions concerning the primary changes initiating these events, the control mechanisms implied and the interrelationship between functional adaptation and hypertrophy remain unanswered.