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Hou JH, Zhu HX, Zhou ML, Le WB, Zeng CH, Liang SS, Xu F, Liang DD, Shao SJ, Liu Y, Liu ZH: Changes in the Spectrum of Kidney Diseases: An Analysis of 40,759 Biopsy-Proven Cases from 2003 to 2014 in China. Kidney Dis 2018;4:10–19
In a very remarkable retrospective “registry-based” study, Hou and colleagues examined the changes in the spectrum of kidney disease derived from careful study of 40,759 native kidney biopsies performed in the Jinling Hospital in Nanjing located in the Jiangsu Province of the People’s Republic of China (population about 12 million, in 2017) between the years 2003-2014. This translates into an approximate renal biopsy rate of about 280 per million persons per year (pmppy) (if the population denominator is a reasonable approximation of the catchment area). If this approximation is valid, then this may be one of the highest renal biopsy rates in the world. By comparison, the estimated (native) renal biopsy rate in the USA (in 2017, including both adults and children) was about 200 pmppy. Only subjects >14 years of age and biopsies with >10 glomeruli were included in the Chinese analysis.
Between 2003 and 2014 the frequency of a biopsy diagnosis of membranous nephropathy (MN) about doubled, diabetic nephropathy (DN) nearly doubled, and monoclonal immunoglobulin deposition disease tripled. In part, these findings might be attributed to a gradual increase in the average age (by about 5 years) of biopsied patients over the periods of 2003-2014. The proportion of subjects biopsied who were over 60 years of age about doubled over this period of time. IgA nephropathy (IgAN) remained as the commonest primary form of glomerulonephritis (GN) but showed a slow decrease in relative frequency over time. The frequency of IgAN peaked at about age 35 years. Focal and segmental glomerulosclerosis (FSGS) was an uncommon diagnosis (only 7.3% of primary glomerular disease). Lupus nephritis (33%) and DN (21%) accounted for 54% of all secondary glomerular diseases. As expected, the finding of DN steadily increased with age of the patients (see figure 1).
Figure 1: Temporal trends of the renal biopsy frequencies of kidney diseases subtypes, 2003-2014. a Frequencies of primary glomerulonephritis subtypes. Percent of all primary glomerulonephritis categories. b Frequencies of secondary glomerulonephritis subtypes. Percent of all secondary glomerulonephritis categories. c Frequencies of tubulointerstitial disease subtypes. Percent of all tubulointerstitial disease categories. d Frequencies of hereditary renal disease subtypes. Percent of all hereditary renal disease categories. From Kidney Dis 2018;4:10–19
These data are likely influenced to some degree by changes in the indications for renal biopsy, a variable that is very difficult to examine in a registry-based data base. Common diseases, like IgAN, increase in frequency in direct proportion to the biopsy rate in the community as a whole. So one cannot assume that the secular changes in biopsy diagnoses reflect a true change in the prevalence of disease. The marked changes in the frequency of MN observed in China are unexplained but might have some connection to environmental factors such as air pollution [1, 2]. The paucity of FSGS as a diagnosis of primary glomerular disease is of great interest, but the lack of differentiation into primary (idiopathic) and genetic forms of this lesion, limit any interpretation.
Nevertheless, large scale epidemiological studies by renal biopsy registries continue to generate some interesting hypotheses concerning etiology of these diseases and have great potential from a public health perspective. Linkage of renal biopsy registries to gene banking programs will likely be of immense value going forward.
References
1. Tang L, Yao J, Kong X, Sun Q, Wang Z, Zhang Y, Wang P, Liu Y, Li W, Cui M, Zhen J, Xu D: Increasing prevalence of membranous nephropathy in patients with primary glomerular diseases: A cross-sectional study in China. Nephrology (Carlton). 2017; 22:168-173
2. Xu X, Wang G, Chen N, Lu T, Nie S, Xu G, Zhang P, Luo Y, Wang Y, Wang X, Schwartz J, Geng J, Hou FF: Long-Term Exposure to Air Pollution and Increased Risk of Membranous Nephropathy in China. J Am Soc Nephrol 2016; 22: 3739-3746
