The kidneys are essential in the maintenance of homeostasis. Renal dysfunction causes multiple, complex effects throughout the body. Kidney function can be impaired acutely, following infection or trauma, or it may develop slowly as a complication of chronic diseases such as diabetes or hypertension. The number of people in New Zealand requiring treatment for renal disease is increasing and incidence is disproportionately high in Mâori and Pacifi c populations, but this is not solely due to their higher incidence of diabetes and hypertension. An appreciation of the roles of the kidney promotes better understanding of the consequences of renal dysfunction. Recognising, and being vigilant for, the complex pathophysiological processes in acute and chronic renal impairment enhances best care for patients.