What Is Nephrotic Syndrome in Children?

Nephrotic syndrome in children is often a sign that the filtering ability of the kidneys may be hindered. It is not a disease in itself but serves as a warning sign that the kidneys will be affected by a disease that prevents glomeruli from properly filtering the blood. The most common symptoms include weight gain and swelling resulting from fluid retention, as well as a decrease in urination. Children ages 1¹/₂ to 5 years old — especially boys — are most likely to have this condition, but adults can also have nephrotic syndrome. Fortunately, few patients suffer permanent kidney damage as a result of nephrotic syndrome in children.

The job of the kidneys is to filter food products, taking out salt, extra water and other unnecessary products. The glomeruli are capillaries in the kidney, and they are responsible for starting the filtering process so the blood can be changed into urine. Proper kidney function results in the blood staying packed with protein, but damaged kidneys allow the protein to stream into the urine. This means the blood does not contain enough protein to properly absorb fluids, which means those fluids enter the body's tissue, leading to swelling.

These problems lead to various symptoms. For example, nephrotic syndrome in children results in a low amount of protein in the blood and a high amount of protein in the urine. While these issues may not be obvious to many patients, a doctor can observe them after taking samples of the blood and urine. The symptoms that patients tend to notice on their own include swelling in the body and resultant weight gain. In addition, children with this condition usually reduce their frequency of urination, which is typically the symptom that leads to a parent scheduling a doctor's appointment for the child.

One of the main causes of nephrotic syndrome in children tends to be minimal change disease, in which patients have kidney biopsies that look almost normal. Doctors typically prescribe prednisone to keep the protein from flowing into the urine, as well as diuretics to increase urination. In some children, this condition is caused by either membranoproliferative glomerulonephritis or focal segmental glomerulosclerosis, both of which are diseases that damage the glomeruli and cause kidney scarring. Prednisone does not work very well to treat such diseases, so many doctors use ACE inhibitors to reduce kidney damage and cytotoxic substances to destroy certain cells. Finally, nephrotic syndrome in children is sometimes caused by congenital nephropathy, resulting in the need for dialysis and an eventual kidney transplant, because this disease does not respond to medication.