An evaluation of preterm kidney size and function over the first two years of life

Abstract

Background We carried out a study to determine the impact of prematurity on kidney development in the first 2 years of life. Methods In this prospective study, extremely preterm neonates (gestation < 28 weeks) were recruited and underwent assessments at 6, 12, and 24 months of age. A cohort of neonates born term were also recruited and followed up for 24 months. The primary outcomes measured in this study were total kidney volume (TKV) and estimated glomerular filtration rate (eGFR); albuminuria and blood pressure measurements (all provided as mean (standard deviation)) were the secondary outcomes. Results Fifty-three premature and 31 term neonates (control) were recruited. At the age of 24 months (corrected age), infants born preterm had significantly smaller TKV (56.1 (9.4) vs. 64.8 (10.2) mL; P = 0.006). There was no difference in eGFR. These preterm infants were smaller (11.25 (1.53) vs. 12.9 (1.8) kg; P = 0.002) and shorter (83.8 (3.0) vs. 86.3 (3.4) cm; P = 0.02) when compared with the control group. At 6, 12, and 18 months respectively, preterm infants had, relative to their height, significantly smaller kidney volumes (0.54 (0.1) vs. 0.59 (0.1) mL/cm, P = 0.05; 0.61 (0.1) vs.0.71 (0.1) mL/cm, P = 0.003; and 0.67 (0.1) vs.0.76 (0.1) mL/cm, P = 0.006). Conclusions Relative to body length, TKV in premature infants is smaller. Since length reflects adult body proportions more accurately than BSA, TKV to height ratio may be a more important measure in the child. Despite smaller TKV (and therefore fewer nephrons), infants born prematurely achieve similar eGFRs in the first 24 months of life, probably due to single-nephron hyperfiltration.

Plasma copeptin is increased and associated with smaller kidney volume in young adults born very preterm

“…Histological analyses of kidney tissues from deceased preterm neonates or biopsies in children reveal a lower glomerular density but an increased glomerular volume when compared with the term controls [ 12 , 36–38 ]. At 2 years of age, children born preterm have a smaller TKV but a similar eGFR [ 13 ]. In our study, we also found a smaller TKV, after adjustment for height, in the preterm group, while eGFR was similar between the groups.…”

“…Most studies on long-term kidney function in preterm children and adults do not report a significant impact on blood creatinine or estimated or measured glomerular filtration rate (eGFR or mGFR) [ 9–11 ]. Kidney histological studies have suggested that preterm neonates show signs of single-nephron glomerular hyperfiltration [ 12 ], and authors have reported a higher eGFR or mGFR per unit of kidney volume in their cohorts of preterm children [ 13 ] or adults [ 11 ], suggestive of the single-nephron glomerular hyperfiltration.…”

Preterm Birth, Kidney Function and Cardiovascular Disease in Children and Adolescents

“…Since there is no non-invasive method for correlating nephron number with kidney mass, many authors have used kidney volume as a surrogate marker ( Table 1 ) [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ]. Several studies have observed that infants and children born preterm had significantly smaller kidney volume or size, as estimated by renal ultrasound, compared with age-matched full-term individuals [ 22 , 26 , 27 , 29 , 30 , 32 , 33 , 35 , 37 , 38 , 39 ]. Similarly, studies that examined the effect of preterm birth on kidney size in adulthood reported significantly decreased kidney length and volume [ 23 , 28 , 31 ].…”

“…However, findings from the studies that have examined long-term renal function after preterm birth are less conclusive. The parameters that have been examined in published literature are microalbuminuria as an early sign of hyperfiltration, albuminuria, levels of blood urea nitrogen, serum creatinine, serum cystatin C, estimated GFR (eGFR), impairments in electrolyte excretions and newer biomarkers of renal dysfunction, such as serum or urine neutrophil gelatinase-associated lipocalin (NGAL), symmetric dimethylarginine (SDMA) and serum b2 microglobulin ( Table 1 ) [ 21 , 23 , 24 , 25 , 27 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 40 , 41 , 42 , 43 , 44 , 45 ]. There are a few studies on school-aged children and adolescents that did not observe any difference in eGFR between ex-preterm and term children [ 24 , 25 , 42 ].…”

Neonatal acute kidney injury: a case-based approach

“…By 2 years of age, GFR reaches the adult value of 120 mL/min/1.73m 2 . GFR maturation appears to be impacted by gestational age, with slower increases seen in prematurely born neonates [9,10]. Tubular function also matures during fetal development, along with an increase in the urinary flow rate.…”