The investigators hypothesize that using Losartan would help decrease proteinuria in pediatric chronic kidney disease with tubular proteinuria.

Children with tubular proteinuria (urine protein to creatinine ratio > 0.3 mg/mg) were randomly assigned in 1:1 ratio to losartan or placebo treatment for 12 weeks, then crossed over to the opposite intervention for another three months after a washout period of 2 weeks. The primary outcome is the change in urinary protein-creatinine ratio from baseline to the end of 12 weeks. Efficacy of losartan in children with CKD with tubular proteinuria was also investigated with additional retrospective review of medical record.

Inclusion Criteria:

• Age: 2years or older and younger than 18 years
• estimated GFR ≥ 30mL/min/m^2
• Mean urinary protein-creatinine ratio > 0.3 g/g from three first-morning spot urine collections
• Renal hypoplasia/dysplasia, Reflux nephropathy, Polycystic kidney disease, Lowe syndrome, Dent disease, Tubulointerstitial nephritis, Nephronophthisis/Medullary cystic disease, Obstructive uropathy(including PUV, UPJ obstruction, UVJ obstruction)

Exclusion Criteria:

• hypertension
• under dialysis or organ transplanted
• bilateral renal artery stenosis or primary hyperaldosteronism
• pregnant or nursing