How is pediatric nephrotic syndrome diagnosed?

Updated: Mar 04, 2020
  • Author: Jerome C Lane, MD; Chief Editor: Craig B Langman, MD  more...
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The first step in evaluating the child with edema is to establish whether nephrotic syndrome is present, because hypoalbuminemia can occur in the absence of proteinuria (such as from protein-losing enteropathy), and edema can occur in the absence of hypoalbuminemia (for example, in angioedema, capillary leak, venous insufficiency, or congestive heart failure).

In order to establish the presence of nephrotic syndrome, laboratory tests should confirm (1) nephrotic-range proteinuria, (2) hypoalbuminemia, and (3) hyperlipidemia. Therefore, initial laboratory testing should include the following [56] :

  • Urinalysis

  • Urine protein quantification (by first-morning urine protein/creatinine ratio or 24-hour urine protein measurement)

  • Serum albumin

  • Lipid panel

Once the presence of nephrotic syndrome has been established, the next task is to determine whether the nephrotic syndrome is primary (idiopathic) or secondary to a systemic disorder and, if idiopathic nephrotic syndrome (INS) has been determined, whether signs of chronic kidney disease, kidney insufficiency, or other renal disorders exclude the possibility of minimal change nephrotic syndrome (MCNS). Therefore, in addition to the above tests, the following should be included in the workup [56] :

  • Complete blood cell (CBC) count

  • Metabolic panel (serum electrolytes, blood urea nitrogen [BUN] and creatinine, calcium, phosphorus, and ionized calcium levels)

  • Testing for human immunodeficiency virus (HIV), hepatitis B and C viruses

  • Complement studies (C3, C4)

  • Antinuclear antibody (ANA), anti–double-stranded DNA antibody, anti-neutrophil cytoplasmic antibodies (in selected patients)

Patients with INS lose vitamin D–binding protein, which can result in low vitamin D levels, and thyroid-binding globulin, which can result in low thyroid hormone levels. Consideration should be given, especially in the child with frequently relapsing or steroid-resistant nephrotic syndrome, to testing for 25-OH-vitamin D; 1,25-di(OH)-vitamin D; free T4; and thyroid-stimulating hormone (TSH).

Other tests and procedures in selected patients may include the following:

  • Genetic studies

  • Kidney ultrasonography

  • Chest radiography

  • Mantoux test

  • Kidney biopsy (age < 1 year or >12 years, or other circumstances)

Age plays an important role in the diagnostic evaluation of nephrotic syndrome. Children younger than 1 year who present with nephrotic syndrome should be evaluated for congenital/infantile nephrotic syndrome. In addition to the tests listed above, infants should have the following tests:

  • Congenital infection (syphilis, rubella, toxoplasmosis, cytomegalovirus infection, HIV infection)

  • Kidney biopsy

  • Genetic tests for NPHS1, NPHS2, WT1, and PLCE1 as guided by biopsy findings and clinical presentation; presence of extrarenal syndromic findings might indicate other genetic testing, such as LAMB2 (Pierson syndrome), LMX1B (nail-patella syndrome), and SMARCAL1 ( Schimke immuno-osseous dysplasia)

Occasionally, a patient with nephrotic syndrome either presents with or develops clinical signs of an acute abdomen, which is frequently due to peritonitis. The diagnosis can usually be made clinically and confirmed by bacteriologic examination of the peritoneal fluid aspirate. The organism most often responsible for the peritonitis is Streptococcus pneumoniae; however, enteric bacteria may also cause peritonitis. Treatment is medical rather than surgical.

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