Acute kidney injury is the abrupt loss of renal function. It is an import health issue in both human and veterinary medicine, with high mortality rate. The currently used diagnostic techniques are imperfect and do not allow timely diagnosis. The aim of this project is to use contrast-enhanced ultrasound, using both commercially available microbubbles and custom made targeted microbubbles, and elastography in the evaluation of dogs with acute kidney injury. The project is divided into 4 parts. Firstly, renal ultrasound parameters in 3 closely related disease entities: acute kidney injury, chronic kidney disease and critically illness, will be established and compared with healthy dogs. In the second study, highly at-risk, critically ill dogs will be studied to establish predictive values in the development of acute kidney injury. Next, follow-up of dogs with acute kidney injury will be performed in the search for predictive parameters for development of chronic kidney disease. Finally, the effect of anti-hypentensive treatment will be evaluated in dogs with acute kidney injury. This project will deliver import novel insights in the diagnostics, monitoring and treatment of acute kidney injury in dogs, improving management of dogs suffering from this disease. Moreover, the dog can serve as a model for human medicine making the results of this research extremely valuable in human medicine.