Acute Kidney Injury: This is a unexpected episode of kidney failure or kidney damage that happens within a few hours or a few days. AKI causes a build-up of waste products in your blood which then makes is difficult for your kidneys to keep a healthy and balanced amount of fluid within your body. AKI can also affect other organs such as the brain, heart, and lungs. This injury is usually common in patients who are in the hospital, in intensive care units, and especially in older adults.