Investigation of pediatric renal transplant recipients with heavy proteinuria after sirolimus rescue

Background. Little is known about the incidence and evolution of proteinuria as a complication of sirolimus rescue in children. This study describes pediatric renal transplant (Tx) recipients who were treated with sirolimus and who developed heavy proteinuria. Risk factors for the development of proteinuria and its time course are explored. Methods. Data at various time points after sirolimus introduction were abstracted from the records of children treated at the author's center. The repeated measures general linear model and the Student's paired t test were used to analyze changes in laboratory values over time. Results. Of the 13 children on sirolimus, 12 developed heavy proteinuria after a mean interval of I month. The mean urine protein (Up)-to-creatinine (c) ratio increased from 1.1 to a peak value of 3.9 (P= 0.003) at 4.6 months after the start of sirolimus. Although not statistically significant, children on no calcineurin inhibitor (CNI) had a greater increase in the Up/c than those on low-dose CNI. At last follow-up, with the use of angiotensin receptor blockers (ARB), the Up/c declined to 2.2. No predictors could be identified for the development of proteinuria. Conclusions. Heavy proteinuria is common after the use of sirolimus as rescue therapy in children with renal Tx. Whether this is attributable to a toxic effect of the sirolimus itself or to lower CNI exposure is uncertain. Early detection of proteinuria is important to enable prompt intervention. Most children have a reduction in their Up/c with the use of ARB and can therefore be continued on sirolimus.