Diabetic kidney disease (DKD) is a common complication in patients with type 2 diabetes. However, the kidneys may also be affected due to non-diabetic kidney disease (NDKD) in these patients. A study published in the December 2022 issue of the BMJ Open Diabetes Research & Care has highlighted the high prevalence of NDKD in type 2 diabetes patients.¹

This single-center study examined 6247 adult patients with type 2 diabetes having  eGFR30–60 mL/min/m2 and/or albumin:creatinine ratio of more than 300 mg/g attending the Endocrinology OPD between March 2017 and March 2021. Patients with advanced kidney disease (eGFR <30 mL/min/m2), UTI (current or past), renal calculi or tumor, patients on antiplatelets or unexplained coagulopathy were excluded in the trial. The aim was to determine the prevalence of DKD, NDKD and mixed kidney disease in type 2 DM patients. The secondary objective of the study was to assess the effectiveness of clinical and laboratory indicators to differentiate DKD from NDKD in selecting subjects for renal biopsy.

Using the traditional discriminators, 869 of the 6247 patients screened had indication for renal biopsy, the discriminators being duration of diabetes, absence of retinopathy, presence of hematuria, RBC cast, presence of markers of possible collagen vascular/connective tissue disorders and autoimmune disorders(c3, c4, ANA, ANCA, PR3 and dsDNA). Biopsy, however, was possible only in 818 subjects. But only 110 patients consented for the same to be included in the final analysis.

Seventy-three (~65%) patients had diabetic kidney disease, 20 (18%) had non-diabetic kidney disease.

IgA nephropathy was the most common NDKD followed by glomerular disease, focal segmental glomerulosclerosis, minimal change disease, amyloidosis (n=1), membranous nephropathy, membranous-proliferative glomerulonephritis, tubule-interstitial disease, acute tubular necrosis and vascular disease, and hypertensive arteriosclerosis.

Seventeen (~16%) patients had mixed kidney disease with characteristics of both diabetic and non-diabetic kidney disease. Focal segmental glomerulosclerosis was the most common NDKD in this group.

Patients with diabetic kidney disease had long-standing disease compared to those with non-diabetic kidney disease. Retinopathy and neuropathy were absent in patients with NDKD. On logistic regression analysis, the duration of diabetes and presence of retinopathy were significantly predictive of DKD on histopathology. The odds ratio (OR) for duration of diabetes was 1.02 and for retinopathy it was 18.85. However, 30% of DKD did not have retinopathy “limiting the utility of the same as a discriminator”.

This study illustrates the high prevalence of non-diabetic kidney disease, either as stand-alone disease or mixed kidney disease, in patients with type 2 diabetes. However, the clinical and/or biochemical measures that were used to predict NDKD were not very useful in either determining or eliminating the need for renal biopsy suggesting the need to define better indicators to identify patients for biopsy and to draw a distinction between DKD and NDKD.

Majority (95%) of the NDKD patients did not have retinopathy; but, 30% of subjects with DKD also did not have retinopathy. Similarly, the disease may have been present long before it is actually diagnosed, ruling out duration of disease as a reliable marker.  “Use of traditional indicators of biopsy would have indicated a need for renal biopsy in 87.2% of subjects, though 64.5% of the subjects had DKD, who would not have benefitted from biopsy,” note the authors. NDKDs are potentially treatable conditions resulting in improved clinical outcomes.

Reference

1. Basu M, et al. Prevalence of non-diabetic kidney disease and inability of clinical predictors to differentiate it from diabetic kidney disease: results from a prospectively performed renal biopsy study. BMJ Open Diabetes Res Care. 2022 Dec;10(6):e003058. doi: 10.1136/bmjdrc-2022-003058.