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Comparison between inulin clearance and endogenous creatinine clearance in newborn normal weight and growth
1Institute for Pathophysiology, Friedrich Schiller University Jena, Germany. rbau@mti-n.uni-jena.de
Insights
Intrauterine growth restriction (IUGR) in piglets impairs renal excretory function. Endogenous creatinine clearance reliably indicates kidney function changes from IUGR and oxygen deprivation in newborn piglets.
Area of Science:
- Neonatal physiology
- Renal function in newborns
- Growth restriction research
Background:
- Intrauterine growth restriction (IUGR) is associated with altered organ development and function in newborns.
- Renal function is critical for neonatal adaptation and survival.
- Understanding the impact of IUGR on renal parameters is essential for clinical management.
Purpose of the Study:
- To investigate the effects of IUGR and acute oxygen deprivation on renal plasma flow (RPF) and excretory function in newborn piglets.
- To evaluate the reliability of inulin and endogenous creatinine clearance as indicators of renal function in IUGR piglets.
- To compare renal responses to hypoxia between normal weight and IUGR piglets.
Main Methods:
- Experiments were conducted on anesthetized newborn piglets (12-27 hours old), divided into normal weight and IUGR groups based on birth weight percentiles.
- Renal plasma flow (RPF), inulin clearance, and endogenous creatinine clearance were measured.
- Severe hypoxia was induced to assess responses to acute oxygen deprivation.
- Arterial blood pressure, heart rate, blood gases, and pH were monitored.
Main Results:
- IUGR piglets exhibited significantly lower inulin and creatinine clearance compared to normal weight piglets (p < 0.01).
- Severe hypoxia reduced RPF and renal excretory function in both groups (p < 0.05).
- Creatinine clearance was consistently higher than inulin clearance in both groups (p < 0.05, p < 0.01), indicating a linear correlation (p < 0.001).
Conclusions:
- Endogenous creatinine clearance is a reliable indicator of renal excretory function in newborn piglets, reflecting both chronic IUGR effects and acute hypoxic insults.
- While creatinine clearance reflects functional changes, it cannot quantitatively determine Glomerular Filtration Rate (GFR) using standard measurement methods.
- The study highlights the vulnerability of renal function in growth-restricted neonates to physiological stressors.
Abstract:
The effect of intrauterine growth restriction (IUGR) and acute oxygen deprivation on renal plasma flow (RPF), renal excretory function (Inulin clearance and endogenous creatinine clearance) and urine flow were studied in twenty newborn piglets 12 to 27 hours old. The experiments were performed on anesthetized animals divided into normal weight piglets and intrauterine growth restricted (IUGR) piglets according to birth weights. The "normal weight" category included animals with a birth weight > 40th percentile (piglets heavier than 1220 g); the IUGR category included animals with a birth weight > 5th and < 10th percentiles (piglets with a birthweight between 733 g and 853 g). This animal model of naturally occurring growth restriction in swine gives asymmetric growth with an increase in the mean ratio of brain weight to liver weight from 1.02 to 2.02 (p < 0.01). There was only a small reduction in brain weight (11%). In contrast, the reduction in weight of liver (55%) and kidney (41%) was proportional to that in body weight (48%). Arterial blood pressure, heart rate, arterial blood gases, pH and RPF were similar in normal weight and IUGR piglets. However inulin clearance and creatinine clearance were significantly lower in the growth restricted piglets (p < 0.01). Severe hypoxia induced a moderate tachycardia, combined with pronounced metabolic acidosis and strongly reduced renal plasma flow and renal excretory function in both groups (p < 0.05). Comparison between inulin and creatinine clearances in normal weight and IUGR piglets revealed a markedly higher clearance of creatinine as of inulin at every experimental stages (p < 0.05, p < 0.01). Alterations of renal excretion due to severe hypoxia and early recovery were similar in both animal groups investigated. Regression analysis rendered a linear correlation between inulin clearance and creatinine clearance among the experimental stages for normal weight as well as IUGR piglets (p < 0.001). Thus, endogenous creatinine clearance is suggested to be a reliable indicator for renal excretory function in newborn piglets. It accurately reflects proportional effects of long-term alterations of renal function due to intrauterine growth restriction as well as acute effects of severe oxygen deprivation. However, using standard methods of plasma and urine creatinine measurement, quantitative determination of GFR by endogenous creatinine clearance is not possible.