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Renal tubular damage in fetuses with intrauterine growth retardation
14th Department of Obstetrics and Gynecology, La Sapienza, University of Rome, Italy.
Insights
N-acetyl-beta-D-glucosaminidase (NAG) levels in amniotic fluid can indicate fetal kidney damage in cases of intrauterine growth retardation (IUGR). High NAG levels correlate with the brain-sparing effect, a sign of fetal distress.
Area of Science:
- Perinatal medicine
- Fetal physiology
- Renal biochemistry
Background:
- Fetal hypoxemia is a common cause of intrauterine growth retardation (IUGR).
- Chronic fetal hypoxia leads to reduced renal blood flow, prioritizing brain perfusion (brain-sparing effect).
- Proximal tubule cells in the kidneys are highly sensitive to hypoxic damage.
Purpose of the Study:
- To measure N-acetyl-beta-D-glucosaminidase (NAG) levels in amniotic fluid.
- To diagnose proximal renal tubule damage in fetuses.
- To correlate amniotic fluid NAG levels with the brain-sparing effect in IUGR pregnancies.
Main Methods:
- Analyzed amniotic fluid from 55 pregnancies (9 IUGR, 46 controls).
- Measured N-acetyl-beta-D-glucosaminidase (NAG) enzyme levels.
- Utilized velocimetric Doppler studies to assess the brain-sparing effect.
Main Results:
- Significantly higher NAG levels were found in amniotic fluid of fetuses with IUGR (p < 0.025).
- 8 out of 9 IUGR fetuses showed elevated NAG levels, indicating renal tubule damage.
- The brain-sparing effect was observed in 8 IUGR fetuses with high NAG levels, but not in the one with normal NAG.
Conclusions:
- Elevated amniotic fluid NAG levels may serve as a biomarker for identifying fetal renal damage in utero.
- This finding aids in diagnosing and monitoring fetuses affected by intrauterine growth retardation and hypoxia.
Abstract:
Fetal hypoxemia is one of the most frequent causes of intrauterine growth retardation (IUGR). In chronic fetal hypoxia, peripheral blood flow and blood flow to the kidneys is reduced to maintain heart, brain and adrenal perfusion, the 'brain-sparing effect'. In kidneys the cells of the proximal tubules seem to be most sensitive to hypoxia caused by reduced blood flow. Damage to the cells of the proximal tubules can be easily diagnosed by urinary levels of N-acetyl-beta-D-glucosaminidase (NAG), an enzyme present in high concentrations in these cells. The aim of the present study was to define the levels of NAG in the amniotic fluid, to diagnose damage to the cells of the proximal renal tubules in fetuses, and to correlate them with a detectable brain-sparing effect. The study was conducted on a total of 55 pregnancies: 9 pregnancies were complicated by IUGR, and the remaining 46 normal pregnancies formed the control group. Higher levels of NAG were detected in the amniotic fluid from the IUGR-complicated pregnancies (p < 0.025). In particular, fetuses with IUGR had high levels of NAG in the amniotic fluid in 8 of 9 cases (+ 2 SD compared with controls), while 1 had normal concentrations. In the 8 cases with high concentrations of NAG in the amniotic fluid, velocimetric Doppler study documented a brain-sparing effect, which was not present in the 1 fetus with normal NAG levels. In conclusion, high levels of NAG in the amniotic fluid may identify in uterus fetuses with renal damage.(ABSTRACT TRUNCATED AT 250 WORDS)