Nephrotic Syndrome

Nephrotic syndrome arises when the glomeruli become damaged and leaky, often through loss of the podocytes that form part of the filtration barrier. Large amounts of protein are lost into the urine (proteinuria), which makes the urine frothy and lowers blood protein levels. In response, the liver senses the protein deficit and increases production of lipids, contributing to dyslipidemia. The fall in blood protein reduces oncotic pressure, allowing fluid to shift into the tissues as peripheral edema; the resulting drop in effective blood volume activates the renin–angiotensin–aldosterone system, increasing water and sodium retention and driving even more fluid into the interstitium.

The dominant feature is swelling — typically around the eyes, then in the legs, ankles, and abdomen — accompanied by frothy urine, weight gain from fluid retention, fatigue, and loss of appetite. The loss of proteins also raises the risk of infection and abnormal clotting.

Diagnosis rests on demonstrating heavy proteinuria together with low serum albumin and raised blood lipids. Urinalysis, serum protein and lipid panels, and renal function tests are used, with a kidney biopsy where the underlying cause needs to be established. The key distinction is from nephritic syndrome, which features blood in the urine and inflammation rather than the heavy protein loss seen here.