Nephrocalcinosis in infants : incidence, risk factors, natural course and renal outcome in certain risk groups
1University of Oulu, Faculty of Medicine, Department of Paediatrics
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|Persistent link:|| http://urn.fi/urn:isbn:951425404X
|Publish Date:|| 1999-09-30
|Thesis type:||Doctoral Dissertation
|Defence Note:||Academic Dissertation to be presented with the assent of the Faculty of Medicine, University of Oulu, for public discussion in Auditorium 12 of the University Hospital of Oulu, on October 29th, 1999, at 12 noon.
Docent Olli Koskimies
Docent Maija Pohjavuori
The aim of the present work was to elucidate the incidence, associated risk factors and natural course of nephrocalcinosis (NC) in very low birth weight (VLBW) infants, and to evaluate renal function in affected infants during early childhood. The occurrence and course of NC in full-term infants receiving furosemide and in infants with congenital lactase deficiency were also studied.
A total of 129 VLBW infants were screened for NC by renal ultrasonography (US) at 2 and 6 weeks and 3 months, and ultrasonic follow-up was performed on the infants with NC at 6, 12, 18 and 24 months, and thereafter annually up to age 5-6 years or until ultrasonic resolution. NC was classified according to its pyramidal localisation and extent. Twenty VLBW children with neonatal NC and 20 control pairs without the condition were examined for renal function at 4.7 (SD 1.1) vs. 4.6 (0.9) years of age. Thirty-six full-term infants who had received furosemide treatment for congestive heart failure for at least 4 weeks and 36 control infants without any diuretic therapy were examined by renal US and by means of a random urine sample taken at a median age of 2.9 vs. 3.4 months. The case records of the 11 infants with congenital lactase deficiency were analysed for NC, and these children were re-evaluated at 2 to 10 years of age.
NC was detected in 26 out of the 129 VLBW infants (20%). The infants with NC were sicker and smaller than the unaffected ones and had more often received furosemide, dexamethasone and theophylline treatment. NC was peripheral in 14 cases (54%), scattered in 7 (27%) and extensive in 5 (19%). All the casesof peripheral NC showed resolution at 12 months, but abnormal renal findings were seen in 3 out of the 7 with scattered NC and 3 out of the 4 surviving children with extensive NC at 24 months, in 2 of whom the condition persisted at age 5-6 years. The children with neonatal NC showed increased urinary calcium and μ2-microglobulin excretion as compared with the controls in early childhood, but there was no significant difference in distal tubular acidification capacity, nor in estimated creatinine clearance.
Five out of the 36 full-term infants receiving long-term furosemide had NC, but none of the controls. The daily dose of furosemide and the urinary calcium concentration were both higher in the infants with NC. Abnormal renal findings were still visible in two of the cases at 24 months of age. Hypercalcaemia was found in 7 out of 10 infants with congenital lactase deficiency tested at the time of diagnosis, and NC was seen in 5 of the 7 cases examined by renal ultrasonography. No constant dysfunction in calcium homeostasis was seen at re-evaluation, but nephrocalcinotic changes were observable in 3 out of the 11 children.
NC may complicate not only the course of VLBW infants, but also that of full-term infants with calciuric medication and diseases that involve hypercalcaemia. Some renal tubular dysfunction may result from NC in former preterm infants, but overall kidney function seems not to be seriously compromised in early childhood.
Acta Universitatis Ouluensis. D, Medica
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