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

Figures & data

Table 1 Baseline Characteristics of the Study Participants

Variables	With Cysts	Without Cysts	Reference Range	p-value
N (M/F)	52 (39/13) ***	119 (54/65)	/	<0.001
Age(year)	67.69±10.21	66.20±12.42	/	0.448
Diabetic Duration(year)	11.80 (1~30)	11.38(1~58)	/	0.764
BMI (kg/m2)	27.01±3.54*	25.48±3.60	18~24	0.011
HbA1c (%)	9.48±2.27	9.64±2.22	4~6%	0.668
Fasting C-peptide (nmol/L)	0.62±0.49*	0.46±0.35	0.27~1.28	0.043
FT3 (pmol/L)	4.14±0.80	4.25±0.50	3.50~6.50	0.377
FT4 (pmol/L)	15.55±2.20	15.29±2.21	11.50~22.70	0.492
TT3 (nmol/L)	1.24±0.33	1.32±0.27	0.92~2.79	0.163
TT4 (nmol/L)	92.01±24.71	92.82±18.19	58.1~140.6	0.817
TSH (mIU/L)	2.02±1.62	2.66±2.47	0.55~4.78	0.094
Left Cyst volume (mm^3)	8292.73±26,967.28	/	/
Right Cyst volume (mm^3)	21,046.66±82,042.27	/	/
Serum creatinine (μmol/L)	105.53±41.48	96.42±100.27	41~73	0.795
Serum uric acid (μmol/L)	350.62±112.95	352.02±111.36	184~464	0.941
eGFR (mL/min*1.73m^2)	65.02±22.71**	76.68±29.21	90~120	0.006
iGFR (mL/min*1.73m^2)	57.84±20.76**	67.58±24.86	80~120	0.001

Notes: *p<0.05; **p<0.01; ***p<0.001.

Abbreviations: HbA1c, glycosylated hemoglobin A1c; FT3, free triiodothyronine; FT4, free thyroxine; TT3, total triiodothyronine; TT4, total thyroxine; eGFR, estimated glomerular filtration rate; iGFR, isotope glomerular filtration rate.

Table 2 The Isotope Glomerular Filtration Rate (iGFR) in T2D with or without Renal Cysts

iGFR (mL/min*1.73m^2)	Cyst	No Cyst	p value
Total iGFR	57.84±20.76	67.58± 24.86	0.001
Left iGFR	27.41±10.34	32.76±13.12	0.001
Right iGFR	30.45±11.93	34.76±12.74	0.001

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.

Note: *p<0.05; **p<0.01;

Abbreviations: BMI, body mass index; iGFR, isotope glomerular filtration rate; eGFR, estimated glomerular filtration rate.

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.

Abbreviations: L-cyst volume, the volume of the left renal cyst; R-cyst volume, the volume of the right renal cyst; iGFR, isotope glomerular filtration rate; eGFR, estimated glomerular filtration rate; L-iGFR, left renal iGFR; R-iGFR, right renal iGFR; BMI, body mass index.

Table 3 A Multilinear Regression Model of Serum Creatinine Level (Represented as Log SCr) in Patients with Renal Cysts

Multilinear Regression	R	0.831	R^2	0.691	Adjusted R^2	0.672
	Variables	B	SE	β	t	Sig	Tolerance	VIF
	Constant	2.116	0.065		32.492	<0.001
	Total iGFR	−0.005	0.001	−0.705	−8.201	<0.001	0.871	1.148
	Gender	0.128	0.032	0.346	4.037	<0.001	0.876	1.142
	Serum UA	0.000282	0.000128	0.195	2.211	0.032	0.829	1.207

Abbreviations: iGFR, isotope glomerular filtration rate; UA, uric acid; SE, stand error; Sig, significance; VIF, variance inflation factor: an indicator for diagnosis of collinearity.

Table 4 A Multilinear Regression Model of iGFR in Patients with Renal Cysts

Multilinear Regression	R	0.823	R^2	0.678	Adjusted R^2	0.651
	Variables	B	SE	β	t	Sig	Tolerance	VIF
	Constant	39.994	12.766		3.133	0.003
	SCr	−0.033	0.046	−0.659	−7.238	<0.001	0.827	1.210
	Gender	10.972	4.423	0.231	2.481	0.017	0.789	1.267
	FT3	8.680	2.375	0.332	3.655	0.001	0.830	1.206
	FPG	1.016	0.435	0.207	2.333	0.024	0.870	1.149

Abbreviations: SCr, serum creatinine; FT3, free triiodothyronine; FPG, fasting plasma glucose; SE, stand error; Sig, significance; VIF, variance inflation factor: an indicator for diagnosis of collinearity.

Table 5 The Gender Disparity in General Characteristics, Renal Cyst Volume, Kidney Function, Glucose Metabolism, and Serum Creatinine Levels

	Male	Female	p-value
Age (year)	66.38±10.01	71.62±10.18	0.122
Duration of T2D (year)	11.17± 7.75	13.69±6.98	0.091
BMI (kg/m^2)	28.87±3.48	27.44±3.85	0.639
Left cysts volume (cm^3)	10.13±30.82	2.77±6.27	0.913
Right cysts volume (cm^3)	11.66±31.83	49.20±155.73	0.108
Total iGFR (mL/min*1.73m^2)	59.63±20.07	52.47±22.69	0.363
Left iGFR (mL/min*1.73m^2)	28.31±10.13	24.69±10.93	0.837
Right iGFR (mL/min*1.73m^2)	31.34±10.94	27.78±14.68	0.844
eGFR (mL/min*1.73m^2)	65.57±23.43	63.36±21.21	0.754
FPG (mmol/L)	8.80 ± 4.54	6.97 ± 2.84	0.097
HbA1c (%)	9.84 ± 2.33	8.42 ± 1.76	0.0501
FPCP (nmol/L)	0.62 ± 0.49	0.62 ± 0.53	0.982
Serum creatinine (μmol/L)	112.13±43.60*	85.74±26.94	0.014

Note: *p<0.05.

Abbreviations: BMI, body mass index; iGFR, isotope glomerular filtration rate; eGFR, estimated glomerular filtration rate; FPG, fasting plasma glucose; HbA1c, glycated hemoglobin A1c; FPCP, fasting plasma C-peptide.

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).

Note: *p<0.05.

Abbreviations: ns, no significant; iGFR, isotope glomerular filtration rate; eGFR, estimated glomerular filtration rate; FPG, fasting plasma glucose; HbA1c, glycosylated hemoglobin A1c; FPCP, fasting plasma C-peptide.

Table 6 The Split Kidney Function Reflected by iGFR and Related Parameters

	Left Renal Cysts	Right Renal Cysts	p-value
Left iGFR (mL/min*1.73m^2)	25.91±10.99	29.30±10.32	0.9174
Right iGFR (mL/min*1.73m^2)	29.78±12.24	32.12±12.74	0.9860
p value	0.8101	0.9740
Left TTP (min)	3.845±1.913	4.414±3.441	0.9788
Right TTP (min)	3.674±2.058	3.993±3.168	0.9991
p value	>0.9999	0.9971
left excrete t1/2 (min)	25.256±14.581	17.859±9.222	0.3818
Right excrete t1/2 (min)	23.985±17.549	18.529±10.322	0.5981
p value	0.9895	0.9991

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).

Abbreviations: ns, no significant; L-iGFR, left kidney glomerular filtration rate; R-iGFR, right kidney filtration rate; TTP, time to peak.

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.