Nephritis (previously called Bright's disease) is an acute or chronic inflammation of the filtering units of the kidneys, caused by an abnormal reaction of the immune system. The reaction often occurs several weeks after a streptococcal infection (usually a sore throat). The immune system produces antibodies which overcome the bacterial infection but which later accumulate in the kidney, causing damage which results in leakage of blood into the urine and inadequate output of urine. In one type of nephritis, the damage is caused by autoimmune antibodies. Acute nephritis is rare, but occurs most often in children. About one in 3000 school-age children develop nephritis. Symptoms include red-brown or smoky coloured urine of reduced amount, puffiness of the eyes and face, sometimes generalised oedema, tiredness and backache. If your child develops these symptoms after a recent sore throat, see your doctor without delay. The diagnosis is made if there are typical abnormalities in the urine and blood together with raised blood pressure and oedema.
Treatment consists of bedrest, diet low in salt and protein, antibiotics to get rid of any remaining infection and in some cases drugs such as diuretics to reduce oedema, drugs to reduce blood pressure if it is dangerously high and corticosteroids to reduce the inflammatory reaction. Usually recovery is complete within two or three weeks. In a few severe cases acute nephritis may become chronic, and may lead to renal failure and uraemia.