A study of size-selective renal elimination using a novel human model

Figures & data

Table 1. Demographics and baseline renal function for the study cohort.

	Mean/no (SD/%)	Interval (min-max)
Male gender	26 (57.8%)
Age (years)	82.0 (5.5)	70–95
Height (cm)	169.8 (8.5)	153–187
Weight (kg)	76.6 (13.4)	46–110
Hypertension	34 (75.6%)
Diabetes	10 (22.2%)
COPD	6 (13.3%)
Previous stroke	6 (13.3%)
Peripheral arterial disease	5 (11.1%)
Atrial fibrillation	18 (40%)
Pre-op creatinine (µmol/L)	89.6 (38.7)	38–241
Pre-op cystatin C (mg/L)	1.5 (0.6)	0.9–3.5
CKD-EPI eGFR creatinine (mL/min/1.73 m^2)	71.5 (20.0)	23–107
CKD-EPI eGFR cystatin C (mL/min/1.73 m^2)	47.1 (17.2)	13–89
CKD-EPI eGFR cystatin C/creatinine (mL/min/1.73 m^2)	59.6 (19.4)	18–95

SD = Standard deviation. COPD = Chronic Obstructive Pulmonary Disease. CKD-EPI eGFR = estimated glomerular filtration rate according to the Chronic Kidney Disease Epidemiology Collaboration.

Figure 1. The left picture shows a pre-procedural CT with A – Inferior vena cava, B – Left renal vein, C – Liver, D – Right atrium. The right picture shows fluoroscopy during the procedure with A – Inferior vena cava with sampling catheter, B – Right renal vein with contrast injection to verify the correct sampling location.

Table 2. Measurement results for analytes.

Analyte	MW (kDa)	N	Arterial conc. Median (IQR)	p-value*	Venous conc. Median (IQR)	RER Mean ± Std	p-value**
urea (mmol/L)	0.06	44	5.9 (5–8)	<0.001	5.6 (5–8)	5.3% ± 3.3%	<0.001
creatinine (µmol/L)	0.11	45	78.0 (59–96)	<0.001	60.0 (48–81)	21.0% ± 6.3%	ref
C-peptide (mmol/L)	3.0	23	1.0 (0.8–1.2)	<0.001	0.8 (0.6–1.1)	17.8% ± 4.6%	0.009
insulin (mIE/L)	5.8	24	6.0 (5–12)	<0.001	5.0 (3–8)	17.8% ± 4.6%	0.010
pro-BNP (ng/L)	8.5	44	1411 (535–2513)	<0.001	1119 (451–2057)	18.0% ± 6.0%	<0.001
β2-microglobulin (mg/L)	12	45	2.6 (2.1–3.3)	<0.001	2.2 (1.9–2.8)	14.1% ± 10.9%	<0.001
cystatin C (mg/L)	13	45	1.2 (1.0–1.5)	<0.001	1.0 (0.9–1.3)	14.4% ± 5.3%	<0.001
troponin-T (ng/L)	36	38	23 (18–36)	<0.001	21 (15–33)	11.3% ± 4.6%	<0.001
orosomucoid (g/L)	44	45	0.7 (0.6–0.9)	0.441	0.7 (0.6–0.9)	−0.2% ± 4.7%	<0.001
albumin (g/L)	66	45	32 (31–34)	0.042	33 (31–35)	−1.7% ± 3.7%	<0.001
IgG (g/L)	150	45	9.0 (7–11)	0.495	9.4 (7–11)	−0.6% ± 5.3%	<0.001

Arterial and venous concentrations are presented on the same row. *Comparisons between arterial and venous concentrations **Comparisons with RER for creatinine. RER = Renal Elimination Ratio. MW = Molecular Weight.

Figure 2. Renal Elimination Ratio (RER) of 11 measured molecules ordered in size from smallest (left) to largest (right). The X-axis on top gives molecular mass in kDa. β2-MG = β₂-microglobulin. Whiskers indicate 95% CI of the mean.

Figure 3. Renal Elimination Ratio (RER, Y-axis) for creatinine vs estimated glomerular filtration rate (eGFR, X-axis) calculated using the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation. The red line indicates the correlation (r = 0.48, p < 0.001) with 95% CI.

Figure 4. Renal Elimination Ratio (RER, Y-axis) for cystatin C vs estimated glomerular filtration rate (eGFR, X-axis) calculated using the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation. The red line indicates the correlation (r = 0.40, p = 0.006) with 95% CI.

Figure 5. Renal Elimination Ratio (RER, Y-axis) of cystatin C vs Renal elimination ratio (RER, X-axis) of creatinine. The red line indicates the correlation (r = 0.69, p < 0.001) with 95% CI.

Data availability statement

Data will be made available by corresponding author upon reasonable request.