ABSTRACT
Objective: Nephrolithiasis and urolithiasis are recurrent conditions associated with significant morbidity and economilc impact. Previous studies have suggested that cell- crystal interactions lead to tubular damage and/or dysfunction. To find further proof for these observations, a metabolic evaluation [including serum and urine biochemistry and urinary enzyme excretion] was done in children with nephrolithiasis and urolithiasis with hydronephrosis
Patients and Methods: This study included two groups: 10 normal children [controls] and 32 children with calcium oxalate urinary tract stones. The latter group was further subdivided into those with nephrolithiasis [n=12] and urolithiasis with hydronephrosis [n=20]. Levels of uric acid, oxalate, calcium, magnesium and inorganic phosphorus in 24-hour urine and serum were determined. Urinary N-acetyl-beta-D-glucosaminidase [NAG], beta-galactosidase [beta-GAL], beta-hexosaminidase [beta-Hex], angiotensin converting enzyme [ACE] and gamma glutamyl transferase [y-GT] levels were also determined colorimetrically
Results: Increases in urinary excretion of oxalate, calcium, magnesium and inorganic phosphorus were the major abnormalities found in stone forming patients. Elevated urinary NAG, beta-GAL, beta-Hex and ACE levels were also noted in patients compared with controls. Urinary excretion of oxalate, NAG, beta-GAL and ACE was significantly elevated in children with nephrolithiasis compared to those with urolithiasis and hydronephrosis
Conclusion: Abnormal urine biochemistry seems to have a role in the risk for urinary-tract stone formation in children. Hyperoxaluria can induce tubular cell injury mainly in proximal tubules, which is more pronounced in children with nephrolithiasis. The tubular injury manifested by enzymuria occurs before alteration of renal functions and blood biochemistry. Urinary tubular enzymes should be screened in children with urinary tract stones