Longitudinal assessment of renal size and function in extremely low birth weight children at 7 and 11 years of age

Abstract

BackgroundThere are a lack of studies describing a longitudinal association between preterm delivery and renal complications later in life. We assessed renal size and function in preterm infants born with extremely low birth weight (ELBW) during 4 years of follow-up, comparing these parameters to age-matched children born full term (term controls).MethodsThe results of selected renal laboratory tests [levels of cystatin C, creatinine, blood urea nitrogen (BUN)] and of renal ultrasound evaluations were compared between the ELBW group and the term control group at age 7 and 11 years.ResultsThe study population consisted of 64 children born with ELBW (ELBW children) who had been recruited at birth and 36 children born at term (term children) who took part in both follow-up assessments. Renal ultrasound examination revealed a significantly smaller renal volume in the 7- and 11-year-old ELBW children compared to the term controls [right kidney volume: 50.8 vs. 61.2 ml/m2, respectively, at 7 years (p <0.01) and 51.4 vs. 58.2 ml/m2, respectively, at 11 years (p <0.01); left kidney volume: 51.4 vs. 60.3 ml/m2, respectively, at 7 years (p <0.01) and 55.2 vs. 60.7 ml/m2, respectively, at 11 years (p = 0.02)]. Renal function in ELBW children was also affected. Serum cystatin C levels were significantly higher in ELBW children than in the controls at 7 years of age, and this difference remained statistically significant at 11 years of age [0.63 vs. 0.59 mg/l, respectively, at 7 years (p = 0.02) and 0.72 vs. 0.61 mg/l, respectively, at 11 years (p = 0.01)]. Six ELBW children also had elevated cystatin C levels (0.97–1.11 mg/l) at 11 years of age. Cystatin C levels were within normal range in the ELBW children at age 7 years and in term children in both follow-up studies. BUN levels were higher in ELBW children at the age of 11 years (4.49 vs. 4.15 mmol/l; p = 0.028).ConclusionContinued follow-up of these patients will reveal whether the observed worsening in renal function will persist into adulthood.

Renal consequences of preterm birth

“…In survivors of extreme prematurity, renal structural and functional differences were noted: smaller kidney volume and higher cystatin C and blood urea nitrogen (BUN) were detectable in 7- to 11-year-old former extremely low birth weight (ELBW) infants compared to infants who were born at term [64]. Follow-up at 6 years showed that survivors of prematurity less than 33 weeks had similar rates of microalbuminuria, but those with additional AKI also had a lower GFR than those without AKI [65].…”

The Impact of Kidney Development on the Life Course: A Consensus Document for Action

“…4 To detect small kidneys, asymmetry, or structural abnormalities, we suggest, if feasible, a baseline renal ultrasound, and follow-up should be performed as indicated [89]. …”

“…In a Norwegian population-based study, the odds of a reduced GFR (<100 mL/min) were 1.66 (95% CI, 1.16-2.37) in men and 1.65 (95% CI, 1.17-2.35) in women who were born SGA compared with AGA, which increased further among those who had been very small for gestational age, demonstrating a dose-response effect [32]. Studies examining renal function after preterm birth have thus far been conducted predominantly in children, and many have described an association with reduced GFR and increased urinary albumin excretion among those who had been born preterm [30,31,87,88,89]. In a cohort of young adults born preterm, birth weight correlated negatively with microalbuminuria and positively with GFR [90].…”

Glomerular Filtration Rate in Former Extreme Low Birth Weight Infants over the Full Pediatric Age Range: A Pooled Analysis

“…Following the search strategy described, 248 (232 + 16) hits were analyzed to result in 6 casecontrol and 3 ELBW cohort studies for the analysis [Figure 1]. The key characteristics of the individual case-control studies are provided in Table 1 [12][13][14][15][16][17][18], cohort studies in Table 2 [19][20][21]. Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 19 January 2020 doi:10.20944/preprints202001.0213.v1…”

“…One study (Krakow cohort) collected Cys C values in the same cohort at the age of 7 and 11 years, and calculated eGFR values in the latest paper [14,18]. To provide an overview on the characteristics, data (eGFR data calculated) reported at the age of 7 years were added to Besides the GFR values, data on other aspects of renal and general outcome (like renal ultrasound, renal tubular functions, blood pressure, biometry and body composition) were coreported.…”