Relationship Between Sporadic Renal Cysts and Renal Function Detected by Isotope Renography in Type 2 Diabetes

Abstract

Purpose: This study aimed to reveal the relationship between the volume of sporadic renal cysts and renal function in patients with type 2 diabetes (T2D).

Materials and methods: One hundred and seventy-one patients that underwent renal imaging and other routine examinations at the Shanghai Pudong Hospital were included in this study. The Gates' method of glomerular filtration rate (GFR) was measured by ^99mTc-DTPA renal dynamic imaging in addition to the eGFR, calculated by the Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI).

Results: Our results showed that BMI, total iGFR, and eGFR showed significant differences between patients with T2D with or without SRC (p < 0.05). Spearman correlation analysis showed that cyst volume was positively correlated with Scr and gender but not iGFR (p > 0.05). The total iGFR positively correlated with eGFR (r = 0.83, p < 0.0001) and negatively with Scr (r = -0.78, p < 0.0001), age (r = -0.43, p < 0.0001), duration of T2D (r = -0.25, p = 0.001), and BMI (r = -0.21, p = 0.006) but not gender (r = -0.03, p = 0.668). The multilinear regression model revealed that gender (β = 0.346, p < 0.001), iGFR (β = -0.705, p < 0.001), and serum uric acid (β = 0.195, p = 0.032) were independent predictors of Scr. Moreover, we observed a significant increase in Scr in males (p < 0.05). Finally, we found that the split kidney function reflected by iGFR and related parameters such as time to peak (PTT) and half time of excretion (excrete t1/2) did not mutually distinguish from each other significantly whether they are measured in patients with renal cysts or in those without renal cysts (p > 0.05).

Conclusion: Our preliminary results suggest that in T2D, SRCs may be a renal complication of diabetic nephropathy. Although we found that the patients with renal cysts may display reduced iGFR, the volume of simple cysts seems not to exacerbate renal insufficiency. Isotope renography is a useful tool to evaluate the split kidney functions in diabetic patients who acquire single-side cysts.

Keywords: SRCs; cysts volume; gender disparity; isotope glomerular filtration rate; kidney function; type 2 diabetes.

Figure 1

The comparisons of age, duration, BMI, iGFR, eGFR, and Scr between T2D patients with or without renal cysts. The results showed significant differences in BMI (C), iGFR (D), and eGFR (E) between T2D patients with and without renal cysts (p<0.05). However, the differences in age (A), duration (B), and Scr (F) did not reach statistical significance.

Figure 2

The heatmap depicts the correlation between cyst volume and other parameters. The correlation coefficient and the significance of critical parameters are shown as described in the text. The gradient in red represents the degree of positive correlation, while the gradient in blue represents the negative correlation, as shown by the color bar on the right side of the map.

Figure 3

Gender disparity in age (A), duration (B), BMI (C), cyst volume (D), iGFR (E), eGFR (F), serum creatinine (G), FPG (H), HbA1c (I), FPCP (J).

Figure 4

Comparison of split kidney function based on iGFR (A), time to peak (B), 1/2 time of excretion (C) coexistence of renal cysts. The figure depicts distinction in iGFR (A), time-to-peak (B), 1/2 time of excretion (C) between the healthy kidney (without cysts) and diseased kidney (with cysts) of the same group (left kidney cysts or right kidney cysts); left iGFR, left TTP, left excrete 1/2 or right iGFR, right TTP, right excrete t1/2 between the different group (left kidney cysts or right kidney cysts).

Figure 5

In T2DM patients, the reduced glomerular filtration rate (iGFR) may be caused by hyperglycemia, hypertension, and hyperlipidemia. The volume of renal cysts did not affect the unilateral kidney’s glomerular filtration rate. The remaining variables, such as cyst location and number, are unknown.