Diagnosis of Second Kidney Disease in Patients with Diabetic Nephropathy

Kidney Week 2020

Researchers, led by Patrick D. Walker, MD, conducted an analysis designed to determine the renal biopsy incidence of a second kidney disease in patients with diabetic nephropathy who were biopsied for various clinical indications. Results of the analysis were reported during a virtual poster session at ASN Kidney Week 2020. The poster was titled In Patients with Biopsy-Proven Diabetic Nephropathy, 38% Have a Second Significant Diagnosis.

Of a cohort of 45,422 non-transplant patients from 2001-2014 (2222 nephrologists in 39 states), 7746 with diabetic nephropathy were identified. Of those 1749 cases were excluded for insufficient data, and 1398 cases with focal segmental glomerulosclerosis were excluded, resulting an analysis cohort of 4599 cases. Patient age ranged from 8 to 89 years and 53.5% were male.

Indications for renal biopsy were acute kidney injury (AKI), acute nephritic syndrome (ANS), rapidly progressive renal failure (RPRF), hematuria, suspected non-diabetic nephropathy renal disease, sudden increase in proteinuria, or chronic kidney disease (CKD).

In 38% of the cases (n=1750), a second kidney disease was diagnosed. The highest odds ratio (OR) of a second diagnosis was in patients with AKI (OR, 3.25; 95% confidence interval [CI], 2.91-3.63; P<.001). ORs in other clinical indications were: ANS, 2.32; 95% CI, 1.59-3.37; P<.001; RPRF, 1.43; 95% CI, 0.93-2.20; P=.099; hematuria, 0.71; 95% CI, 0.54-0.93; P=.012; non-diabetic nephropathy, 0.64; 95% CI, 0.45-0.90; P=.01; proteinuria, 0.36; 95% CI, 0.32-0.40; P<.001; and CKD, 0.03; 95% CI, 0.01-0.08; P<.001.

There was a correlation between age and a second diagnosis (P<.001); the incidence ranged from 29% in patients <30 years of age to 56% in patients ≥80 years of age.

In 1589 patients, a specific second kidney disease was to be ruled out. A second kidney disease was found in 48% of renal biopsies with a rule-out diagnosis versus 33% when no rule-out second disease was given (OR, 1.83; 95% CI, 1.62-2.08; P<.001). There was significant correlation of grades of diabetic nephropathy and a second kidney disease diagnosis: I-75%, II-64%, III-38%, IV-20% (P<.001).

“In biopsy-proven diabetic nephropathy, a significant second kidney disease was found in 38%, with AKI and ASN most likely to yield a second kidney disease. Age and a rule-out second kidney disease can further differentiate patient groups most likely to have a second kidney disease. Given the worldwide toll of diabetes, the finding of a potentially treatable second kidney disease in diabetics already at high risk of end-stage kidney disease should provide significant savings in morbidity, mortality, and healthcare expenses,” the researchers said.

Source: Walker PD, Charu V, Dai D-F. In patients with biopsy-proven diabetic nephropathy, 38% have a second significant diagnosis. Abstract of a poser presented at the American Society of Nephrology virtual Kidney Week 2020 (Abstract PO0955), October 22, 2020.