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Kidney Week

Abstract: FR-PO1001

Total Nephron Number and Renal Histopathological Lesions in IgA Nephropathy

Session Information

Category: CKD (Non-Dialysis)

  • 2102 CKD (Non-Dialysis): Clinical, Outcomes, and Trials

Authors

  • Marumoto, Hirokazu, The Jikei University School of Medicine, Tokyo, Japan
  • Tsuboi, Nobuo, The Jikei University School of Medicine, Tokyo, Japan
  • Sasaki, Takaya, The Jikei University School of Medicine, Tokyo, Japan
  • Okabayashi, Yusuke, The Jikei University School of Medicine, Tokyo, Japan
  • Haruhara, Kotaro, The Jikei University School of Medicine, Tokyo, Japan
  • Kanzaki, Go, The Jikei University School of Medicine, Tokyo, Japan
  • Koike, Kentaro, The Jikei University School of Medicine, Tokyo, Japan
  • Kawamura, Tetsuya, The Jikei University School of Medicine, Tokyo, Japan
  • Yokoo, Takashi, The Jikei University School of Medicine, Tokyo, Japan
Background

IgA nephropathy (IgAN) is the most frequently occurring primary glomerulonephritis. It is histopathologically characterized by various degrees of glomerulosclerosis together with a series of active proliferative lesions, which represent a process of progressive loss of functional nephrons. To date, total nephron number has not been evaluated in relation to the histopathological findings of IgAN due to the technical difficulties in counting nephrons in a clinical setting.

Methods

The histopathological findings in diagnostic biopsies of IgAN patients were evaluated based on the Oxford international classification and the Japanese histological grade. The latter is a lamped scoring system of glomerular lesions exhibiting cellular or fibrocellular crescents, segmental sclerosis, and global sclerosis. Total nephron number was calculated using a simplified method based on the combined use of unenhanced computed tomography and stereology-based estimation of non-sclerotic glomerular density on renal biopsy (Sasaki T et al. 2018, ASN).

Results

A total of 107 cases (age 43, male 54%, estimated glomerular filtration rate 61.5 ± 24.2 ml/min/1.73 m2, urinary protein excretion 1.4 ± 1.6 g/day) were included. The frequencies of the Oxford classifications were as follows: M (0, 51%; 1, 49%), E (0, 88%; 1, 12%), S (0, 10%; 1, 90%), T (0, 74%; 1, 20%; 2, 6%) and C (0, 64%; 1, 36%), respectively. The frequencies of the Japanese histological grades were as follows: H-I, 56.1%; H-II, 28.0%; H-III, 13.1%; and H-IV, 2.8%. Among all patients, the total nephron number ranged from 78,000 to 1,989,000. Total nephron number was significantly associated with the S score (p < 0.042) and the T score (p < 0.001), but was not associated with the M, E and C scores of the Oxford classification. Moreover, total nephron number significantly decreased in parallel with increasing Japanese histological grade (p < 0.001). Multivariate analyses showed that the associations between total nephron number and the T score or H-grade were independent of age, amount of urinary protein excretion, and renal function at the time of biopsy.

Conclusion

These results suggest that the total nephron number may be associated with certain histopathological lesions and thus may be involved in the progression of renal injuries in IgAN.