URINARY SATURATION AND NEPHROCALCINOSIS IN PRETERM INFANTS - EFFECT OF PARENTERAL-NUTRITION

Urinary lithogenic and inhibitory factors were studied in 27 preterm i nfants; 16 had total parenteral nutrition (TPN) and 11 had breastmilk with an additional glucose-sodium chloride infusion. Urines were colle cted for 24 hours on day 2 (period A), day 3 (B), and once between day s 4 and 10 (C). Urinary calcium oxalate saturation was calculated by t he computer program EQUIL 2. Renal ultrasonography was performed every second week until discharge. The calcium/creatinine ratio increased i n infants on TPN (A 0.91; C 1.68 mol/mol) and was significantly higher at period C than that in infants on breastmilk/infusion (A 0.52; C 0. 36). The oxalate/creatinine ratio was persistently higher with TPN (20 3 mmol/mol) than with breastmilk/infusion (98; 137). The citrate/creat inine remained constant with TPN (0.44 mol/mol), whereas it increased significantly with breastmilk/infusion (0.26; 0.49). Calcium/citrate r ose considerably with TPN, but decreased with breastmilk/infusion to a significantly lower level than with TPN. The urinary calcium oxalate saturation increased with TPN (2.4; 4.5) and decreased with breastmilk /infusion (2.1; 1.5) to a significantly lower value than with TPN. Nep hrocalcinosis developed in two infants on TPN. Mean daily calcium inta ke was similar in both groups, whereas protein, sodium, and phosphorus intake were significantly higher on TPN. It is concluded that the inc rease in urinary calcium oxalate saturation observed with TPN is due t o the combined effect of an increased urinary calcium excretion and hi gher urinary oxalate/creatinine and calcium/citrate ratios. The change s observed are likely to be caused by TPN itself, which differs in sev eral respects from breastmilk feeding.