Association of urinary sediments with renal pathological patterns in IgA nephropathy

Abstract

Objective To investigate the relationship between urinary sediments and renal pathological patterns in IgA nephropathy. Methods A total of 516 specimens of fresh fasting morning urine were collected. Urinary specimens were processed routinely and examined with phase-contrast microscopy. Urinary sediments were classified into three types according to the components: type Ⅰ: hematuria containing dysmorphic red blood cells(RBCs); type Ⅱ: active urinary sediments containing hematuria and casts of RBCs, and/or a few casts containing white blood cells or epithelial cells; type Ⅲ: advanced urinary sediments containing hematuria, and various casts consisted of red and white blood cells, renal tubular epithelial cells, and waxy casts. Pathological patterns of IgA nephropathy were classified according to the descriptive diagnosis of pathological lesions. Statistical analysis were performed using kappa test, Χ2 test, and significance was accepted at P<0.05. Results The pathological patterns of 516 cases of IgA nephropathy included focal proliferative pattern in 75.2%, mesangial proliferative pattern in 7%, proliferative and sclerosing pattern in 6.8%, endocapillary proliferative pattern in 2.9%, crescentic pattern in 2.3% respectively. Hematuria was present in 74.8% (386/516 cases) of patients before renal biopsy, 15.7% of them had gross hematuria. Urinary sediments of 386 cases consisted of 54% of type Ⅰ, 35% of type Ⅱ, and 11% of type Ⅲ respectively. Type Ⅰ urinary sediment was present in focal proliferative pattern without active lesions, its concordance was 79.4%; while type Ⅱ were mainly seen in cases with glomerular and/or tubulointerstitial active lesions; type Ⅲ were seen in crescentic or endocapillary proliferative patterns and/or cases with active tubulointerstitial lesions. The concordance of type Ⅱ and type Ⅲ urinary sediments with active glomerular and tubulointerstitial lesions in IgA nephropathy was 79.2%. There was a significant difference in urinary sediment types between active and non-active pathological lesions (P<0.01). Multivariate analysis indicated urinary sediment types independently predicted the active and non-active lesions in IgA nephropathy (P<0.01, OR=7.268). Conclusions Urinary sediment analysis is an easy and valuable method to predict the active and non-active lesions of renal pathology in IgA nephropathy, can be used as a non- invasive indicator of clinical course. Key words: IgA nephropathy; Urinary sediment spectrum; Renal biopsy, Phase-contrast microscopy