Background Carotid intima-media thickness (cIMT) may identify early alterations in the vascular phenotype in children with chronic kidney disease (CKD).Methods and Results Investigation of longitudinal changes in cIMT SD scores (SDS) in 670 patients from the 4C Study (Cardiovascular Comorbidity in Children With CKD Study), aged 6 to 17 years, with CKD stage 3 to 5 at baseline. The longitudinal trajectory of cIMT SDS over up to 8 years was examined using a longitudinal mixed-effects model. The yearly progression rate in cIMT SDS (beta=0.20 [95% CI, 0.13-0.28]) remained positive during the initial 4.5-year follow-up period but slowed down quadratically with increasing observation time (beta=-0.02 [95% CI, -0.03 to -0.01]). Risk factors for increased cIMT SDS included time since baseline, younger age, higher height SDS, female sex, elevated diastolic blood pressure, and lower serum albumin, but not estimated glomerular filtration rate. In patients with progressive CKD, higher albuminuria was additionally associated with an increase in cIMT SDS. In patients with stable CKD, serum phosphate and time were the only risk factors identified for elevated cIMT SDS. Annual rates of change in blood pressure were positively correlated with the rate of change in cIMT SDS within the first 4.5 years (for systolic: beta=0.42 [95% CI, 0.22-0.62]; for diastolic: beta=1.56 [95% CI, 1.01-2.11]).Methods and Results Investigation of longitudinal changes in cIMT SD scores (SDS) in 670 patients from the 4C Study (Cardiovascular Comorbidity in Children With CKD Study), aged 6 to 17 years, with CKD stage 3 to 5 at baseline. The longitudinal trajectory of cIMT SDS over up to 8 years was examined using a longitudinal mixed-effects model. The yearly progression rate in cIMT SDS (beta=0.20 [95% CI, 0.13-0.28]) remained positive during the initial 4.5-year follow-up period but slowed down quadratically with increasing observation time (beta=-0.02 [95% CI, -0.03 to -0.01]). Risk factors for increased cIMT SDS included time since baseline, younger age, higher height SDS, female sex, elevated diastolic blood pressure, and lower serum albumin, but not estimated glomerular filtration rate. In patients with progressive CKD, higher albuminuria was additionally associated with an increase in cIMT SDS. In patients with stable CKD, serum phosphate and time were the only risk factors identified for elevated cIMT SDS. Annual rates of change in blood pressure were positively correlated with the rate of change in cIMT SDS within the first 4.5 years (for systolic: beta=0.42 [95% CI, 0.22-0.62]; for diastolic: beta=1.56 [95% CI, 1.01-2.11]).Conclusions The results show a significant longitudinal increase in cIMT SDS in children with CKD. Changes in blood pressure are associated with the progression of cIMT SDS, suggesting a relevant impact of blood pressure modulation on cIMT SDS.< Réduire