Nephrotic syndrome

Nephrotic syndrome is a disorder where the kidneys have been damaged, causing them to leak protein from the blood into the urine. It is a fairly benign disease when it occurs in childhood, but may lead on to chronic renal failure, especially in adults, or be a sign of an underlying serious disease such as systemic lupus erythematosus or a malignancy. more...

Signs and symptoms

• The most common sign is excess fluid in the body. This may take several forms:
  • Puffiness around the eyes, characteristically in the morning.
  • Edema over the legs which is pitting (i.e. leaves a little pit when the fluid is pressed out, which resolves over a few seconds).
  • Fluid in the pleural cavity causing pleural effusion.
  • Fluid in the peritoneal cavity causing ascites.
• Thrombosis
• High levels of cholesterol (hypercholesterolemia)
• Renal failure
• Hypertension (rarely)
• Some patients may notice foamy urine, due to a lowering of the specific gravity by the high amount of proteinuria. (Actual urinary complaints such as hematuria, or oliguria are uncommon, and seen often in nephritic syndrome.)
• Hypoalbuminemia

Diagnosis

Other causes of edema are congestive heart failure and cirrhosis. High urine levels of protein can readily be detected with a dipstick. The best way to make a diagnosis is to quantify the amount of protein in a 24-hour urine sample or a random albumin to creatinine ratio (ACR). A diagnosis of nephrotic syndrome requires more than 3.5 grams of proteinuria per 1.73 square metre surface area in adults. Additional components of the nephrotic syndrome include hypercholesterolemia and low serum albumin levels.

Pathogenesis

The glomeruli of the kidneys are the parts that normally filter the blood. They consist of capillaries that are fenestrated (leaky, due to little holes called fenestrae or windows) and that allow fluid, salts, and other small solutes to flow through, but normally not proteins.

In nephrotic syndrome, the glomeruli become damaged due to diabetes, glomerulonephritis, or even prolonged hypertension (high blood pressure) so that small proteins, such as albumin can pass through the kidneys into urine.

Nephrotic syndrome is characterised by proteinuria (detectable protein in the urine), and low albumin levels in blood plasma. As a compensation, the liver begins to make more of all its proteins, and levels of large proteins (such as alpha 2-macroglobulin) increase.

Edema usually occurs due to salt and water retention by the diseased kidneys as well as sometimes due to the reduced colloid oncotic pressure (because of reduced albumin in the plasma). Cholesterol levels are also increased, and though the mechanism isn't fully understood, it is thought to be due to the increased synthesis of lipoproteins in the liver. There is an increased tendency for thrombosis (up to 25%), perhaps due to urinary loss of inhibitors of clotting such as antithrombin III.

Similar loss of immunoglobulins increases the risks of infections and relevant immunisation is recommended against pneumococcus, Haemophilus influenzae, and meningococcus.

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