What tests are used to diagnose nephrotic syndrome?
Your doctor can diagnose the problem by examination and by ordering blood and urine tests. The blood test can show how low the protein level is, and even more importantly show that the kidney function is otherwise normal, which it often is.
Protein can be found in the urine by putting a special dipstick into a urine sample. Your child’s pediatrician can administer this quick test of the urine in their office. If the test is positive for protein, it’s still possible that it may be a “false positive,” so the doctor will send your child’s urine to a laboratory for a more specific measurement.
If the second test reveals that there really is proteinuria present, the doctor will order some routine blood work to ensure the kidneys are otherwise working well. The doctor may include another testing of the urine and possibly an ultrasound of the kidneys, just to make sure there are no other related problems. All this can be done routinely as an outpatient, unless your child is sick (very commonly, the child will not be sick at all).
In mild cases, where the amount of protein is higher than normal but not considered very high, one of the next steps is to measure the amount of protein in urine that is collected in the bladder when lying down. That specimen will likely be collected first thing after getting out of bed and taken to the laboratory for protein measurement. If this sample has a normal amount of protein, it means “extra” protein only leaks into the urine during upright posture. This type of protein leak is not considered a problem, and requires no further attention. If the proteinuria is not related to posture, it may still not be a problem, but your child’s doctor will continue measuring it every 4-6 months to see if clears up on its own. If there is a steady increase in proteinuria, your doctor will refer you to a nephrologist.