The impact of prematurity on postnatal renal medulla development

Abstract

Background: In humans, nephrogenesis ceases before birth but the renal medulla continues to develop postnatally and reaches full functional maturation at around 12-18 months of age. Premature birth is associated with reduced nephron number and increased risk of kidney and cardiovascular disease. However, the impact of prematurity on renal medulla remodelling and maturation and its contribution to the development of adult disease is unknown. Methods: Preterm babies born at ∼28 weeks of gestation and term babies without renal or urinary tract abnormalities were included in this study. Renal ultrasound was performed in 35 premature babies at 32 weeks and 37 weeks post menstrual age (PMA). In addition, 42 babies born at term were examined in the first week of life. Additional ultrasound images were taken at six months of age in all babies. Total kidney volume, renal cortical and pyramid thickness were measured. Results: In premature babies the average kidney volume increased significantly from 32 weeks to 37 weeks PMA (post menstrual age) (6.89 ± 0.4 vs 10.38 ± 0.29, p ≤ 0.0001). However, at 37 weeks PMA the kidney volume and the pyramid/cortex ratio were still significantly smaller in premature babies compared to term babies (10.38 ± 0.29 vs 12.85 ± 0.48, p ≤ 0.0001; 2.22 ± 0.08 vs 2.79 ± 0.08, P = 0.0001 respectively). Premature infants also had a significantly lower eGFR (73.6 vs. 79.3 mL/min/1.73 m2; p = 0.03). By 6 months the average kidney volume was no longer different between premature and term babies due to significant catch-up growth of the premature kidney. The pyramid/cortex ratio remained significantly lower in the premature babies than term babies (2.01±0.05 vs 2.5±0.10, p = 0.0006). In term babies the medulla region continued to develop and mature; renal pyramid/parenchyma ratio increased from birth to 6 months (0.59±0.01 vs 0.62±0.05, p = 0.05). For premature babies the pyramid/parenchyma ratio didn't change significantly from birth to 6 month suggesting the medullary growth was significantly impaired. Conclusions: Taken together, these results suggest that premature birth has sustained effects on postnatal renal medulla development and remodelling with potentially negative impact on renal function later in life.L6337003602020-12-23 <br />