Progression to hypertension in non-hypertensive children following renal transplantation.

BACKGROUND The aim of this study was to evaluate in non-hypertensive children following renal transplantation (TX) the rates and determinants of transition to hypertension. METHODS Retrospective case note review of all current paediatric kidney transplant patients in the UK. At baseline (6 months following TX), all included subjects were non-hypertensive with systolic and/or diastolic clinic blood pressure (BP) ≤95th percentile while on no anti-hypertensive therapy. We assessed progression from optimal (systolic and/or diastolic clinic BP<50th percentile), normal (systolic and/or diastolic clinic BP≥50th but <90th percentile) and pre-hypertension (systolic and/or diastolic clinic BP 90th-95th percentile) to hypertension (systolic and/or diastolic clinic BP>95th percentile). If systolic and diastolic BP levels belonged to different categories, the higher of the two levels were used for categorization. RESULTS At baseline, 146 of 524 (27.9%) children (106 male) median [inter-quartile range (IQR)] age 7.8 years (4.8, 11.8) were non-hypertensive and not on any anti-hypertensive therapy; there were 34 patients (23.2%) with optimal BP, 90 (61.6%) with normal BP and 22 (15.1%) with pre-hypertension. They were followed up for a median of 2.0 (1.0, 4.0) years post-TX. At the end of follow-up, BP was optimal in 37 patients (25.3%), normal in 35 (24.0%), high normal in 2 (1.4%) and 72 (49.3%) had progressed to hypertension. The Kaplan-Meier estimated time at which 50% of patients developed hypertension was 2.0 years for the pre-hypertension and 3.0 years in the normal BP group as opposed to 40% risk at 7-year post-TX in the optimal group (P=0.001 between the three groups). The differences between BP groups remained significant after adjustment for all risk factors on multivariate analysis. CONCLUSIONS Just over 49% of our initially non-hypertensive patients progressed to hypertension following TX. BP needs careful monitoring post-TX and ideally should be maintained in the 'normal' and 'optimal' range.