Background: The effects of hematuria on the outcome of IgA nephropathy (IgAN) remain unknown and treatment of IgAN with severe hematuria is controversial.
Methods: Eighty-eight IgAN patients with proteinuria <0.5 g/day and who had not received corticosteroids, immunosuppressive agents, or undergone a tonsillectomy were divided into two groups: (1) patients with low (<20/high-power field [HPF]) urinary red blood cell (U-RBC) counts (L-RBC group, n = 48); and (2) patients with high (≥20/HPF) U-RBC counts (H-RBC group, n = 40). Clinical and histological findings, renal survival rate and risk factors for progression were analyzed.
Results: The male ratio and blood pressure were significantly higher in the L-RBC group. Median proteinuria, mean estimated glomerular filtration rate and histological findings according to Oxford classifications were similar. During the 5 years after renal biopsy, the median amount of proteinuria remained at <0.5 g/day or g/g creatinine in both groups, and the median U-RBC decreased to <10/HPF in both groups without any intensive therapy. The 15-year renal survival rate, estimated using the Kaplan-Meier method, was 100 % in the H-RBC group, but decreased to 83.4 % in the L-RBC group, although it was not significant. The treatment of inhibitors of renin-angiotensin system (RAS inhibitors) decreased the risk for progression by Cox regression analysis (hazard ratio: 0.14, p = 0.027).
Conclusion: Severe hematuria at the time of biopsy naturally improved without any intensive therapy, and there were no negative effects of hematuria on the outcome of IgAN with mild proteinuria. Its prognosis was relatively good, and the treatment of RAS inhibitors might prevent from progression.
Keywords: Hematuria; IgA nephropathy; Mild proteinuria; Renal function; Urinary red blood cells.