Abstract 1672: Glomerular Insufficiency, An Early Marker Of Renal Dysfunction In Patients With A Fontan Circulation.
Introduction: Fontan circulations have high central venous pressures and low dynamic cardiac output, risk factors for depressed renal perfusion.
Objectives: Hypothesizing subclinical renal dysfunction, we sought to characterize renal pathophysiology and cardio-renal interaction in this group.
Method: 17 Fontan patients were tested for early morning urine cystatin C, alpha-1-microglobulin (A1M), retinol binding protein (RBP), protein:creatinine and albumin:creatinine ratio; serum cystatin C (S.Cys-C) and creatinine; echocardiography including Tissue Doppler (TDI); and renal Doppler.
Results: 6 (mean age 22.8 ± 5.0years) of 17 patients (mean age 23.5 ± 4.2years) had subclinical renal dysfunction, mean S.Cys-C-derived glomerular filtration rate (GFRS.Cys-C) 77.31 ± 7.82ml/min/1.73m2, vs. 114.21 ± 36.38ml/min/1.73m2 in the remainder. Whilst GFRS.Cys-C correlated highly with 2-D visual assessment of systemic ventricular function (correlation=0.618; p=0.014) this was not the case for any TDI parameters. Tubular function indices (urine cystatin C, RBP and A1M) were normal. Glomerular function indices were abnormal for S.Cys-C, with mean 1.04 ± 0.06mg/L, range 0.97–1.11mg/L; (normal range:0.53–0.95mg/L). Gross morphological renal abnormalities included 3 abnormal bipolar sizes in both right (mean 9.13 ± 0.49cm) and left (mean 9.38 ± 0.66cm) kidneys (normal range>10cm), 6 and 5 abnormal renal cortical thicknesses in right (mean 11.61 ± 1.27mm) and left (mean 12.31 ± 0.92mm) kidneys respectively (normal range>13mm) and 1 mild scarring of the right kidney. Abnormal resistive indices were present in the right kidney of 3 patients (mean 0.79 ± 0.01, range 0.78–0.80), and in the left kidney of 2 patients (mean 0.83 ± 0.02, range 0.81–0.84). Patients with abnormal resistive indices (>0.77) had lower arterial saturations (mean 88.67 ± 2.08%, range 87–91% vs. mean 94.77 ± 2.46%, range 90–97% in those without) and higher haematocrit (mean 0.49 ± 0.01L/L, range 0.48–0.49L/L vs. mean 0.46 ± 0.03L/L, range 0.42–0.52L/L in those without).
Conclusion: Fontan patients often have subclinical renal dysfunction mainly due to glomerular insufficiency. Ventricular function, cyanosis and polycythemia appear to be important drivers for renal dysfunction.