Category Archives: Renal

Tip 70: hyponatraemia in preterm babies

Hyponatraemia is common in preterm babies, with up to a third of very low birth weight infants being hyponatraemic in the first week after birth. This is commonly due to: impaired reabsorption of sodium at the proximal tubule; immature up-and-down … Continue reading

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Tip 68: postnatal diuresis

At birth, body weight in water is ~80–85% at 26–31/40 and ~75% at term. An abrupt reduction of the interstitial fluid occurs shortly after birth, usually on day 2-3, triggered by atrial natriuretic peptide. This is delayed in babies with … Continue reading

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Tip 57: posterior urethral valves

In bilateral antenatal renal pelvis dilatation, an urgent ultrasound scan is needed after birth to look for residual significant renal pelvis dilatation (over 10mm) and any dilated ureter or thickened bladder wall that may signify posterior urethral valves. A normal … Continue reading

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Tip 55b: fluid losses in preterm babies

Babies <1.5kg commonly require: high infusion rates (80-100ml/kg/day) of 10% dextrose on day 1 diligent review of their fluid balance and clinical picture with reduction in fluids if required (e.g. hyponatraemia) delayed sodium supplementation until a significant diuresis has occurred … Continue reading

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Tip 202: assessing neonatal renal function

Serum creatinine levels, a proxy to glomerular filtration rate in neonates, should fall rapidly over the first few days of life, typically 70-90 mmol/litre (reflecting maternal levels) to 30 mmol/litre. A sustained rise in serum creatinine (or failure to fall) … Continue reading

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Tip 158: antenatal renal pelvis dilatation 2

Antenatal renal pelvis dilatation is considered significant if the anteroposterior diameter is >5 mm in the second trimester or >7 mm in the third trimester and postnatally. Ultrasound should also note: renal size and parenchyma ureteric and bladder dilatation amniotic fluid … Continue reading

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Tip 154: normal kidney size

As a rough guide, the 10th centile for normal renal length (in mm) is equivalent to the baby’s gestation in weeks. E.g. 27/40 = renal length 27mm (10th centile). Reference: Chitty, L. S., & Altman, D. G. (2003). Charts of fetal size: … Continue reading

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