Nephritis, nih FRY tihs, formerly called Bright's disease, is a general term for several inflammatory diseases of the kidneys. Glomerulonephritis is the disease most often called nephritis. It involves an inflammation of the glomeruli (filtering units) of the kidneys. The inflammation often reduces the amount of urine produced by the kidneys, causing waste products normally eliminated in the urine to accumulate in the body. Severe or persistent glomerulonephritis can cause serious, permanent damage to the kidneys.