Small Kidney Size Possible Indication of Increased Mortality Risk From Diabetes

Patients with diabetes who have small kidney size at the start of peritoneal dialysis (PD) face a substantially higher risk of death than those with enlarged or normal size kidneys, according to a new study.

The multivariate statistical analysis found mortality was more than 6 times likelier for patients with small kidneys (odds ratio, 6.452; 95% CI, 1.220-34.482, P = .028), a study in Scientific Reports found.

Half of the patients with small kidney size died (n = 8) vs 9.0% (n = 6; P <.001) of patients with normal or enlarged kidney size, the study found. Furthermore, there was more infection-related mortality in patients with small kidneys than those with normal or enlarged kidneys (43.8% vs 7.5%; P <.001), with 7 of the 8 deaths of those with small kidneys from infection.

The study was conducted by researchers in Taiwan, where the incidence and prevalence of end stage kidney disease (ESKD) is the highest in the world. In 2016, Taiwan’s incidence was 493 patients per million, far ahead of the United States, which had 378 per million.

Most patients who have ESKD with high levels of urea in their blood are treated with hemodialysis in Taiwan; this study involved those treated with PD. In Taiwan, there has been a trend of shifting from hospital-based care of older patients to home-based care, where PD can take place, the authors noted. Most families in Taiwan are large families, the authors noted, so that there tend to be younger family members around who can take care of older parents undergoing PD.

The study involved 83 patients with diabetes receiving PD in the hospital setting between 2015 and 2019. Most had normal or enlarged kidney size (n = 67; 80.7%) at the start of PD; the remainder had small kidney size (n = 16; 19.3%).

The study also identified several common traits among those with small kidney size, an uncommon condition among patients with diabetes. Patients had a mean (SD) older age, 76.63 (10.63) vs 68.03 (11.26) years (P = .007); had a longer mean diabetes duration, 272.09 (305.09) vs 151.44 (85.31) months (P = .006); and were predominantly female (75.0% vs 41.8%; P = .017).

Additionally, they had lower serum levels of creatinine, at 9.63 (2.82) vs 11.74 (3.32) mg/dL (P = .022), and albumin, at 3.23 (0.67) vs 3.60 (0.47) g/dL (P = .010).

Patients with diabetes have a propensity to develop infections, the authors noted, because the hyperglycemic environment supports immune dysfunction, such as the impairment of neutrophil function, suppression of the antioxidant system, and humoral immunity. In addition, the presence of enlarged kidneys is far more common in patients with diabetes than those with small kidneys. A recent study found the presence of diabetes was associated with a 1.723-fold risk of having a large kidney. Enlarged kidneys predict poor outcome in patients with diabetes and chronic kidney disease.

The authors said older age, longer duration of diabetes, and malnutrition (lower blood creatinine and albumin levels) could be correlated with increased mortality.

This is the first study, they concluded, to compare outcomes between patients with diabetes who have enlarged or normal kidneys vs those with small kidneys.

Reference

Chen C-H, Chen C-Y, Yu M-C, et al. Impact of kidney size on mortality in diabetic patients receiving peritoneal dialysis. Sci Rep. 2021;11(1):8203. doi:10.1038/s41598-021-87684-z