A total of 32 children (20 boys and 12 girls) with RCAD syndrome were retrospectively analyzed using the medical records of three tertiary pediatric nephrology centres in Prague, Jena, and Munich. The inclusion criteria were genetically proven RCAD syndrome (whole HNF1B-gene deletion or pathogenic variant of the HNF1B-gene in combination with presence of any renal anomaly) and office BP data. Children with CKD stage 5 were excluded from the study. The median age was 3.0 years (range 0.3-18.5 years). The HNF1B-gene deletion was found in 72 % of patients and a pathogenic variant of the HNF1B-gene in 28 % of patients. Renal ultrasound was pathological prenatally in 48 % of patients and postnatally in 52 % of children. The median age at diagnosis was 3.0 years (range 1 day – 18 years).
Three (9%) children received ACE-inhibitors for hypertension and/or proteinuria. No child received any other antihypertensive medication at the time of the study.
Office blood pressure measurement
Office BP was measured using an oscillometric device Omron and hypertension (HT) was defined as systolic and/or diastolic BP ≥ 95th percentile according to the current ESH guidelines  and/or the use of antihypertensive medication.
Ambulatory blood pressure monitoring (ABPM)
ABPM was performed in 7 patients because of elevated OBP (n=2) or because of CKD despite of normal OBP (n=5). In the remaining 25 patients ABPM was not performed mainly because of normal office BP. ABPM studies were carried out using oscillometric SpaceLabs 90207 or 90217 monitors (SpaceLabs Medical, Redmont, WA). An appropriate cuff was placed on the non-dominant arm by a physician who also informed the child and parents in detail how to operate the monitoring system. Monitors were programmed to measure BP automatically every 20 min during the day and every 30 min at night. The criteria for omitting BP outliers from ABP recordings were systolic BP >200 and <70 mmHg, diastolic BP >150 and <40 mmHg, and mean arterial pressure (MAP) >200 and <40 mmHg. According to the reference values by Wuhl et al. , data were analyzed by using an individualized daytime and nighttime period according to the individual diaries. Mean systolic and diastolic BP at daytime and nighttime were calculated. The BP index was calculated as mean BP, divided by the 95th percentile that was determined according to the body height and sex of the patient . For children with body height <120 cm the 95th percentile was used for children with body height 120 cm. Ambulatory HT was defined as systolic and/or diastolic mean BP at daytime and/or nighttime ≥95th percentile.
Urinary excretion of albumin and protein
Freshly voided urine (first morning urine) was obtained for quantitative measurement of total protein (Biuret method), albumin (turbidimetry) and creatinine (enzymatic). Pathological albuminuria was defined as albumin/creatinine ratio >3 mg/mmol creatinine and proteinuria as protein/creatinine ratio >22 mg/mmol creatinine .
Chronic kidney disease (CKD) stages 1 – 4 according to the K-DOQI guidelines were detected [K-DOQI] using estimated glomerular filtration rate according to the Schwartz formula using serum creatinine (enzymatic method) and body height . Children with CKD stage 5 were excluded from the study.
Data on renal ultrasound findings were collected (cysts, renal length, dysplasia, dilation of renal pelvis). Kidney lengths were analysed, compared with normal standards and expressed as SDS .
Echocardiogram (standard two-dimensional echocardiogram (GE/Wingmed system 5, Vivid 7, Horten, Norway) was performed in 8 children on the same day as the office BP measurement (according to the recommendations of the American Society of Echocardiography) . Left ventricular mass (LVM), was calculated according to the formula of Devereux from the left ventricular internal dimension at end diastole, interventricular septal thickness and left ventricular posterior wall thickness . Left ventricular mass was indexed to height2.7 (left ventricular mass index LVMI) to account for body size . Left ventricular hypertrophy (LVH) was defined as LVMI ≥95th percentile for normative pediatric LVMI data .
The extra-renal findings (maturity onset diabetes of the young - MODY, hypomagnesemia or liver abnormalities) and medical history data such as birth weight or oligohydramnios were collected retrospectively from the medical charts.
The data were analysed by using the STATA software package. SDS values of hypertensive and normotensive patients were investigated by using the Mann-Whitney U test. Values with p<0.05 were considered statistically significant.