Glomerulonephritis refers to inflammation and damage affecting the glomeruli—the tiny filtering units inside the kidneys. When these filters are damaged, blood or protein can leak into the urine. Depending on the type and severity, glomerulonephritis may be associated with blood or protein in the urine, swelling, high blood pressure, or changes in kidney function. There are several possible causes, including infections, immune-related conditions, inherited disorders, and other diseases. Evaluation may involve blood and urine tests, while additional investigations, including a kidney biopsy, may be required in some cases to identify the specific type of disease. Treatment depends on the underlying cause and severity. This article explains the condition, its possible signs, diagnosis, and treatment approach.