The Relationship Between Kidney Size and Blood Pressure Values in Children With Autosomal Dominant Polycystic Kidney Disease

Objective: To assess the relationship between kidney size and blood pressure (BP) in children with autosomal dominant polycystic kidney disease (ADPKD). Design and method: Our retrospective cross-sectional study included 139 children with ADPKD (median age 9.9±5.3 years; 52% boys). PKD1 mutations were identified in 50 patients (36%) and PKD2 in 7 (5%); in 82 patients (59%) diagnosis was based on clinical criteria and familiar history. We analyzed antropometric data, BP and kidney size parameters assessed by ultrasound (USG) and magnetic resonance imaging (MRI. Hypertension was diagnosed using office BP and ambulatory blood pressure monitoring (ABPM). Results: Median kidney length (KL) SDS measured by USG was 1.25 [0.43–2.49], and kidney volume (KV) SDS was 1.94 [0.99–3.22]. Corresponding MRI values were 1.58 [0.44–2.70] for KL and 2.63 [1.83–4.01] for KV. KL above the 97.5th percentile was observed in approximately 32.5% of patients in both modalities. Enlarged KV was more frequent, affecting 47.5% of patients in USG and 61.5% in MRI. Patients with PKD2 mutations presented milder disease (0–5 cysts per kidney) compared with other genetic backgrounds, who more often developed >10 cysts per kidney (p=0.027). Mean KL assessed by USG was greater in patients with PKD1/PKD2 mutations than in those without molecular confirmation (104.0 [91.6–121.0] vs 97.5 [82.3–112.3] mm; p=0.042). Hypertension was diagnosed in 28.5% of patients, with no differences between genetic groups. Kidney size parameters were significantly associated with BP. Patients with increased KV (>97.5th percentile) had significantly higher 24-hour MAP compared with those with normal KV (median 89.2 [85.6–93.8] vs 82.5 [78.9–86.7] mmHg; p<0.001). KL showed weak-to-moderate correlations with 24-hour mean arterial pressure (MAP), stronger for MRI than for USG (R=0.37, p=0.019 vs R=0.29, p=0.011). The strongest association was observed for KV SDS measured by USG (R=0.61, p=0.0045), while KV assessed by MRI also correlated with MAP (R=0.35, p=0.0087). Conclusions: Kidney size is significantly associated with BP in children with ADPKD irrespective of kidney size assessment method. KV correlates with BP better than KL, with USG-derived KV showing the strongest association.