Urinary concentration is the result of a complex glomerulotubular mechanism, which culpits with the stimulation of aquaporins at the collector tubule, in response to vasopressin (ADH). Water renal management is one of the earliest defects in chronic kidney disease (CKD). The most useful test to know the urinary concentration ability is the calculation of the urinary volume by 100 ml of GFR (V) and the desmopressin test. Few studies have analyzed the urinary concentration ability in kidney trasplant patients (KT).

AIMS: Analyze water management in KT, compared with a healthy group. Analyze the value of these markers as prognostic factors for renal function at 4 years of follow-up.

METHODS: Urinary volume (V)was calculated:Creatp/Creatu x 100 ml GFR (%). Urinary osmolality was measured after sublingual administration of 20 mcg of desmopressin. We considere "concentration defect" when maximum urinary osmolality (Osmu) was <800 mOsm/kg.

RESULTS: 100 KT patients were studied, 68% male, 51,6±12,3 yr (21-79) and duration of KT of 7,8±5,8 yr. 21% of patients had presented acute rejection before, and 7% had chronic allograft dysfunction. 84% of patients were on triple therapy (78% FK, 20% cyclosporine). Control group was formed by 69 volunteers, 43% male, 31±7,7 yr.

Mean levels of Osmu in KT were very low compared with the control group (635,98±157,89 vs 1020,16±113,85 mOsm/kg, p<0,05). However, V was higher in the KT group (2,64±2,26 vs 0,71±0,24%, p<0,05). This indicates that KT patients show polyuria and urinary concentration defect. We found urinary concentration defect in 86% of KT and a high V (>1,1 ml/100 ml of GFR) in 78%.

Classifying patients by quartiles of GFR, we observed significant lower levels of Osmu and higher levels of V as GFR decreases. However, up to 70% of KT with GFR>60ml/min, showed urinary concentration defect. We found that Osmu was associated with GFR at 4 years of follow-up (r=0,417,p<0,001). Linear regression analysis showed that Osmu was independently associated (Beta:-0.338, p=0,038) with GFR at 4 years of follow-up.

CONCLUSIONS: Urinary concentration defect is very prevalent in KT patients, even with GFR>60 ml/min, and this is associated with a worse renal prognosis at 4 years of follow-up.

CITATION INFORMATION: Garcia-Garcia P, Jarque A, Rivero A, Rodriguez A, Gonzalez Posadas J, Macia M, Garcia Nieto V, Navarro J. Urinary Concentration Ability in Kidney Transplant Patients as Predictor for CKD. Am J Transplant. 2017;17 (suppl 3).

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