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[Enzymuria and kidney diseases in childhood]
Insights
Urinary enzyme tests, including N-acetyl-beta-D-glucosaminidase (NAG) and alanine aminopeptidase (AAP), are sensitive indicators of kidney damage in children. However, these tests lack specificity for pinpointing the exact cause of renal dysfunction.
Area of Science:
- Pediatric Nephrology
- Clinical Biochemistry
- Toxicology
Background:
- Urinary enzyme excretion is a potential biomarker for renal health.
- Assessing kidney function in children requires sensitive and non-invasive methods.
Purpose of the Study:
- To evaluate urinary enzyme excretion (NAG and AAP) in children with various diseases.
- To determine the utility of enzymuria in diagnosing renal disorders and monitoring treatment.
Main Methods:
- Measured urinary N-acetyl-beta-D-glucosaminidase (NAG) and alanine aminopeptidase (AAP) activities in 316 children.
- Compared enzyme levels across healthy children, those with renal diseases, post-transplant patients, and those on specific medications.
- Correlated enzymuria with proteinuria and clinical parameters.
Main Results:
- Urinary NAG and AAP decreased with age in healthy children.
- Enzyme excretion significantly increased in children with nephrotic syndrome, tubulopathies, and chronic renal failure.
- Elevated NAG and AAP were observed during cyclosporine A treatment and tobramycin exposure.
- Enzymuria was not consistently elevated in children with diabetes mellitus or those on NSAIDs.
Conclusions:
- Urinary NAG and AAP are sensitive indicators of renal damage in children.
- Enzymuria assays are valuable but lack specificity for differentiating glomerular vs. tubular dysfunction.
- Combined use of enzymuria and proteinuria analysis offers a more comprehensive assessment of renal integrity.
Abstract:
Urinary enzyme excretion and proteinuria were studied in 316 children with different underlying diseases. Activities on N-acetyl-beta-D-glucosaminidase and alanine aminopeptidase decreased progressively with age in the urine of 66 healthy prematures, newborns, infants or children. In 51 children with nephrotic syndrome, tubulopathies or chronic renal failure, excretion of NAG and AAP rose 3 to 30 fold. Contrary to molecular weight dependent protein analysis, determination of enzymuria did not allow to differentiate between glomerular and tubular disorders. After renal transplantation, 31 out of 52 children had a pathological enzymuria. NAG and AAP were more frequently elevated during treatment with cyclosporine A (21/29), than with azathioprine (10/23). The influence of nephrotoxic drugs upon enzymuria was documented in 14 children with cystic fibrosis or septicaemia treated with tobramycin. Activities of NAG and AAP rose transiently, whereas proteinuria remained almost unchanged. Only three out of 45 children receiving nonsteroidal antiinflammatory drug therapy for juvenile rheumatoid arthritis or spondylarthritis showed a pathological increase in enzymuria. Mean urinary NAG and AAP excretion in 154 children with insulin dependent diabetes mellitus were not different from controls and were unrelated to either duration of disease or HbA1 concentration. The determinations of urinary enzymes as non-invasive tests of renal integrity in medicine and toxicology provide a very sensitive indicator of renal damage. The assays of NAG and AAP have proven to be most valuable; however, due to a lack of specificity for the type and origin of renal dysfunction, these urinary enzyme assays are most useful when carried out in conjunction with electrophoretic analyses of proteinuria.