It has been known for well over a half century that radiological contrast agents are able to cause nephropathy. Patients who already have renal insufficiency are particularly at risk of this. The practice of offering MRI investigations for this population has been called into question since specifically in patients with renal disease nephrogenic systemic fibrosis can be caused by gadolinium-based contrast agents. Contrast agents and the kidney - as a target but also the starting point of injury - are therefore closely related to each other. In this book, renowned experts summarise the various aspects of this relationship with the aim of creating a rational basis for the use of contrast agents.