Increased porosity of the kidney filter system to protein, permitting heavy protein loss in the urine, and thus blood protein deficiency. This in turn leads to a decline in the blood’s capacity to retain moisture, causing oedema in body tissue, principally in the face and legs. Fluid can also accumulate in the abdominal cavity (ascites). Blood fat content usually rises at the same time. A form of nephrotic syndrome occurs in children in which typical globules of fat are excreted in the urine (lipid nephrosis). The cause of this condition is unknown. In 75 per cent of adults with nephrotic syndrome the cause is a kidney disorder such as glomerulonephritis. The other 20 per cent are caused by general diseases such as diabetes mellitus, pre-eclampsia, amyloidosis in rheumatic conditions, and malaria. Diagnosis is by removal of a piece of kidney tissue with a hollow needle for tests (biopsy). Treatment is with a high-protein diet to compensate for protein loss, and salt limitation and diuretics to reduce fluid accumulation. Further treatment depends on the cause of the syndrome.