To explore the correlation of microscopic hematuria with pathological parameters in IgA nephropathy (IgAN) patients with mild proteinuria.

A retrospective study was performed in primary IgAN patients with urinary protein <0.5 g/24 hours but no gross hematuria, who were first diagnosed by renal biopsy at the Chinese PLA General Hospital from January 1, 2007 to December 31, 2012. Clinical indicators were collected within 1 week before renal biopsy, including blood pressure, urinary protein quantitation, urinary red blood cell morphology and count, and renal function, etc. Pathological lesions were evaluated according to the updated Oxford classification method. The correlation of microscopic hematuria with pathological indicators was analyzed with the Poisson regression model.

A total of 88 IgAN patients with urinary protein <0.5 g/24 hours were included in the study, among whom there were 22 cases without microscopic hematuria, 58 cases with non-full-field microscopic hematuria, and 8 cases with full-field microscopic hematuria. Poisson regression model analysis showed that the levels of microscopic hematuria were correlated with both the mesangial hypercellularity lesion (OR 4.92, 95%CI 1.75-13.83) and the crescents formation lesion (OR 6.55, 95%CI 2.68- 15.98), after adjustment of the patient′s urinary protein and renal function (eGFR) levels. And there is an interaction between the mesangial hypercellularity lesion and the segmental glomerulosclerosis lesion (OR 3.82, 95%CI 1.30- 11.25).

Proliferative lesions, including mesangial hypercellularity lesion and crescents formation lesion, were the main pathological factors associated with the microscopic hematuria in the IgAN patients with mild proteinuria (<0.5 g/24 hours). The mesangial cell proliferative lesion coexisting with the segmental sclerosis lesion had an significantly-increased correlation with the microscopic hematuria.