It is an acute inflammation of the kidney which follows a few weeks after an infection with Streptococcus. The infection is usually of the skin (i.e. impetigo) but may follow a throat infection (therefore often called acute post-streptococcal glomerulonephritis). The inflammation of the kidney is the result of an unusual response to the infection by the body’s immune system. Antibodies produced against the Streptococcus damage the kidney. This is similar to the immune response which results in acute rheumatic fever. Again, the reason for this unusual response is not fully understood.
Damage to the glomeruli of both kidneys results in blood and protein leaking into the urine and a decrease in urine production. Retained fluid causes oedema and fluid overload. Although there are many causes of glomerulonephritis, acute glomerulonephritis is usually post-streptococcal. Proteins from specific strains of Group A Streptococcus combine with antibodies and complement to form immune complexes which are deposited in, and damage, the glomeruli.