Serum uromodulin as a marker of kidney graft function*

Abstract

Serum uromodulin (sURO) was recently found as a sensitive tubular marker in early chronic kidney disease stages. Thus far, mainly early uromodulin urinary excretion was tested in kidney recipients. The aim of our study was to conduct a long-lastinlong-term assessment of sURO in kidney graft function monitoring. Forty-one stable kidney recipients (aged 47 (13.7)) were studied around the 3<sup>rd</sup> month (3m) and the 2<sup>nd</sup> year (2y) after kidney transplantation. Sera were tested for sURO, creatinine and tacrolimus levels. Kidney biopsy was scored according to revised Banff 97 classification. sURO level (mean 66.06ng/ml at 3m; 77.81 at 2y) increased borderline significantly (P = 0.051) in time and significantly correlated with eGFR (3m RS = 0.46; 2y RS = 0.58), creatinine levels (RS respectively –0.55 and –0.56) and donor age (3m Rs = –0.33; 2y RS = –0.41). We observed borderline correlations between sURO and Banff biopsy scoring: 3m-sURO with arteriolar hyalinosis-ah (RS = –0.3, P = 0.06) and 2y-sURO with peritubular capillaritis-ptc (RS = 0.45, P = 0.07). Correlations of sURO with 3m tacrolimus levels (Rs = 0.3, P = 0.08) were borderline, however patients with CNI toxicity lesions in biopsy had sURO significantly lower (mean 3m-sURO 52.7 vs 83.1 ng/ml; 2y-sURO 61.9 vs 98.1 ng/ml). sURO can reflect kidney graft quality and function. sURO correlated with ptc, which is considered to be an early marker of a chronic antibody-mediated graft injury. Tacrolimus doesn’t influence sURO levels directly, but sURO is lower in patients with toxic kidney injury in biopsy.