THE DIFFERENTIAL DIAGNOSTIC-VALUE OF URINARY ENZYME AND AMINO-ACID EXCRETION IN CHILDREN WITH NEPHROTIC SYNDROME

Urinary enzymes N-acetyl-beta-D-glucosaminidase (NAG) and gamma-glutam yl transpeptidase (gamma-GT) are sensitive markers of specific renal c ell damage. Excessive urinary amino acid excretion may also be an indi cator of renal tubular damage. We have evaluated urinary excretion of NAG, gamma-GT and 37 amino acids, phospholipids and dipeptides in 30 c hildren (aged 2.3-18.1 years) with nephrotic syndrome (NS), 23 with mi nimal change nephrotic syndrome (MCNS), 7 with focal segmental glomeru losclerosis (FSGS) and 16 healthy age-matched controls. Nine MCNS pati ents were in relapse and 14 in remission. Enzyme activity is expressed as micromoles per milligram urinary creatinine. In FSGS, NAG excretio n correlated with the following: blood urea nitrogen (BUN) (r = 0.8), serum protein (r = 0.57), serum cholesterol (r = 0.85), serum albumin (r = -0.68) and proteinuria (r = 0.56). In FSGS the gamma-GT excretion was not significantly different from MCNS in remission or in relapse. In FSGS, gamma-GT excretion correlated with the following: BUN (r = 0 .48), serum creatinine (r = -0.66), serum protein (r = -0.54), serum a lbumin (r = -0.68) and serum cholesterol (r = 0.87). Compared with con trols, the urinary excretion of 5 amino acids was increased in FSGS pa tients as a possible indicator of tubular damage. The value for 7 amin o acids was reduced in MCNS patients. Urinary amino acid excretion was not different from controls for the other amino acids in either FSGS or MCNS. These data suggest that urinary enzyme excretion, particularl y NAG excretion, and amino acid excretion may be useful in the diagnos is and degree of disease in these histological forms of NS in children .