Nephrotic Syndrome

Nephrotic syndrome is a clinical syndrome caused by increased glomerular permeability to plasma proteins. Injury to the glomerular filtration barrier lets albumin and other plasma proteins escape into the urine in large quantities. The result is heavy proteinuria, hypoalbuminaemia and oedema, frequently with hyperlipidaemia and lipiduria. It describes a pattern, not a cause, so finding the pattern is the start of the work-up rather than the end of it. The thresholds differ by age. For adults, KDIGO 2021 uses urine protein excretion of at least 3.5 g/24 hours or a urine protein-to-creatinine ratio (PCR) of at least 300 mg/mmol, with hypoalbuminaemia; oedema and hyperlipidaemia are variable. For children aged 1 to 18 years, KDIGO uses a first-morning urine PCR of at least 200 mg/mmol or a dipstick protein of 3+ or higher, with serum albumin below 30 g/L, or oedema when no albumin result is available. An adult figure is never applied to a child, and a paediatric figure is never applied to an adult. The visible problem is swelling. The less visible problems are reduced effective circulating volume, thrombosis,...