Preterm Infants and Nephrocalcinosis

Study Overview
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Brief Summary
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Nephrocalcinosis (NC), defined as calcification of renal tissue, has been reported to occur in 7-41% of premature infants. Causes of NC are likely multi-factorial, and infants born prematurely and with very low birth weight (<1500 gm) seem to be at the highest risk of developing NC. Recent changes in recommendations for nutrition for the preterm infant such as higher intakes of protein, calcium, and vitamin D may also play a factor in the pathogenesis of NC. Currently, diagnosis of NC often occurs incidentally during ultrasound evaluation for other issues. Because there is no acute symptom or pattern of symptoms in the preterm population associated specifically with NC, it is possible that many cases of NC may not be diagnosed. Presently, it is impractical and costly to screen all infants for NC with renal ultrasound, therefore there is no standard of care regarding screening for NC. NC may have long-term effects. Studies have shown that preterm infants with NC had shorter kidneys and a lower rate of tubule resorption of phosphorus (TRP) than preterm infants without NC. This study will analyze weekly urinalysis for all enrolled subjects prospectively and then look at the incidence of NC at discharge of the enrolled subjects.

Official Title
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Preterm Infants and Nephrocalcinosis: Diagnosis and Pathogenesis

Conditions
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Prematurity, Nephrocalcinosis, Hypercalciuria

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Infants whose gestation less than or equal to 32 weeks and/or birth weights less than 1800 gm Exclusion Criteria: Infants with congenital abnormalities of the heart, lung, GI, or kidneys that will affect renal function.

Ages Eligible for Study
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Maximum Age: 2 Weeks

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Non-NC group<br>Enrolled subjects who did not have evidence of NC on renal ultrasound | |
| NC group<br>Enrolled subjects who did have evidence of NC on renal ultrasound | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Urinary calcium to creatinine ratio (UCa/Cr) | Beginning within the first two weeks of life, urine calcium to creatinine ratio (UCa/Cr) will be analyzed weekly through discharge and then correlated to renal ultrasound results done prior to discharge. | 3 months | 
| Urinary crystals | Beginning within the first two weeks of life, urinalysis for evidence of urinary crystallization will be analyzed weekly through discharge and then correlated to renal ultrasound results done prior to discharge. | 3 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Serum Vitamin D levels | Serum vitamin D levels will be analyzed and compared in infants with NC against infants without NC (controls). | 3 months | 
| Vitamin D intake | Daily vitamin D intake will be recorded from participants' medical records and will be analyzed and compared in infants with NC against infants without NC (controls). | 3 months | 
| Calcium intake | Daily calcium intakes will be recorded from participants' medical records and will be analyzed and compared in infants with NC against infants without NC (controls). | 3 months | 
| Protein intake | Daily protein intakes will be recorded from participants' medical records and will be analyzed and compared in infants with NC against infants without NC (controls). | 3 months | 
| Total bone density per DXA | Whole body bone density per dual energy X-ray absorptiometry (DXA) will be done on all enrolled participants at discharge and will be compared between infants with and without NC. | 3 months | 
| Tibial bone density per tibial ultrasound | Tibial body bone density per ultrasound will be done on all enrolled participants at discharge and will be compared between infants with and without NC. | 3 months |