Topic overview

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Acute kidney injury is an abrupt fall in glomerular filtration that can produce azotemia, with or without reduced urine output. It is classified as prerenal, intrinsic, or postrenal; clues such as sodium excretion and urine concentration help distinguish reduced perfusion from parenchymal injury. Acute tubular necrosis is a common intrinsic pattern, with characteristic casts and epithelial changes. Chronic kidney disease is persistent kidney damage or reduced filtration over at least three months. Nephron loss can drive further injury, while laboratory findings may include azotemia, mineral-bone abnormalities, anemia, and acidosis. The full topic connects these diagnostic patterns with complications and management principles, including treatment of the underlying cause and attention to medication safety.