Purpose
Haematuria and proteinuria may point to kidney diseases, but may also be found incidentally. Among schoolchildren, many studies suggest their prevalence to around 1%. In neonates, the frequency and persistence of haematuria and/or proteinuria in the general population have so far not been investigated systematically.
Methods
In the course of the prospective KUNO-Kids Health Study, urine samples were collected and analysed by dipstick in asymptomatic neonates on days three to five after birth. Those with positive findings underwent a maximum of two follow-ups until 16 weeks of age and factors associated with haematuria and/or proteinuria were explored.
Results
Of 509 participants with a urine sample available, 27% (n = 139) exhibited positive results. Of these, 58% (n = 81) had isolated haematuria, 21% (n = 29) had isolated proteinuria, and 21% (n = 29) had both. Of all children with positive urine tests, 76% (n = 105) underwent a first follow-up (mean 7 weeks later), and only in 1.9% (n = 2) was a positive result found. In the second follow-up (mean 2 weeks later), no positive results were detected anymore. Positive urine test results were more common in females and after vaginal delivery (p < 0.001 and p = 0.037, respectively).
Conclusion:
The present study identified haematuria and/or proteinuria in a significant proportion of healthy newborns shortly after birth, but results returned to normal within weeks in all participants available for follow- up. Thus, isolated findings of haematuria and/or proteinuria in newborns should be interpreted with caution.