DECREASED URINARY CITRATE LEVELS AS A MARKER OF PROGRESSIVE DETERIORATION OF GLOMERULAR FILTRATION IN PATIENTS WITH AUTOSOMIC DOMINANT POLYCYSTIC KIDNEY DISEASE (ADPKD)

Abstract BACKGROUND AND AIMS In a previous work we have found that there is a reduction in urinary citrate levels in autosomic dominant polycystic kidney disease (ADPKD) patients. Their levels are related to GFR but not serum bicarbonate levels. Our aim was to analyse whether there is any relationship between rate of GFR deterioration and citraturia in ADPKD patients. METHOD We collected routinary determinations of urine citrate in 24-h urine samples and analysed its predictive role for GFR deterioration with general linear modelling. RESULTS We included 94 patients, 42 ± 14 years old, 59.6% men and 40.4% women. Follow-up from citrate determination 55 ± 28 months (range 16–119). Baseline data: urea 40.2 ± 12.3, Cr 1.15 ± 0.38 mg/dL, GFR 78 ± 26 mL/min/1.73 m2. Bicarbonate 25.1 ± 2.5 (18.2–29.2) mEq/L. Final GFR: 69 ± 32 mL/min/1.73 m2. GFR variation: −2.23 ± 4.14 mL/min/year (range −13.7 to 10). We classified patients according to urinary citrate tertiles (≤117, 117 to ≤ 303, >303 mg/gCr). GFR was different at baseline (67.5 ± 27.9, 74.3 ± 24.3, 92.4 ± 19.7, respectively, P < 0.001) and at final observation (51.1 ± 31.8; 71.4 ± 30.1; 85.3 ± 24.9, respectively P < 0.001). There were no differences in albuminuria or proteinuria at baseline, but there were differences in uric acid serum levels and urine output. There were no differences in follow-up time. We observed that GFR rate was different according to tertiles: −4.62 ± 3.66, −0.58 ± 2.78 and −1.53 ​​± 4.74 mL/min/year, respectively (P < 0.001). When comparing CKD by stages, we found that patients with citrate ≤ 117 mg/gCr showed higher GFR rates than when they had higher levels: CKD1 −7.74 ± 3.37, CKD2 −4.5 ± 4.4, CKD3 −3.04 ± 1.79 versus citrate patients > 117 mg/gCr with deterioration < 2 mL/min/year (P < 0.05). With multivariate analysis, we found that final GFR was positively associated with baseline GFR and negatively with age, follow-up time and citrate levels ˂ 117 mg/gCr. CONCLUSION Urinary citrate levels decrease as GFR reduction is observed in ADPKD. The reduction of urinary citrate to values ≤ 117 mg/gCr is associated with faster deterioration of renal function in patients with ADPKD.