Hypercalcaemia in infants with posterior urethral valves - a retrospective study in a UK tertiary paediatric centre
INTRODUCTION:Infants with posterior urethral valves (PUV) were noted to have hypercalcaemia on routine blood chemistry in our single UK tertiary paediatric centre. There is limited literature to explain this finding and guide management in these infants. Hypercalcaemia can cause long term sequelae if untreated, such as hypertension, nephrocalcinosis, nephrolithiasis, and chronic kidney disease.We undertook a retrospective case note review of patients with PUV to ascertain whether there is an association between PUV and hypercalcaemia. Secondary aims includedestablishing thetiming of hypercalcaemia, its durationand relation torenal function.
METHODS: Electronic departmental records were used to identify relevant cases. Data extracted included; adjusted calcium, creatinine, PTH, 25 hydroxyvitamin D, 1-25 dihydroxyvitamin D, and phosphate.All data is from the 1st year of life, in patients with confirmed PUV. Hypercalcaemia was defined as 3 consecutive readings of adjusted calcium >2.8mmol/L in a 1 week interval. Patients with adjusted calcium levels over the reference range (2.74mmol/L) but not fulfilling our definition were described as ‘borderline’.Data regarding long term complications were collected, including hypertension, nephrocalcinosis, nephrolithiasis and CKD.
RESULTS: 101 patients were identified over 15 years (2000-2015). 24 were excluded due toinsufficient data in their first year of life, and 4 as they were born with renal failure requiring renal replacement therapy.In total 73 patients were included. 28.8% (21/73) had hypercalcaemia, of which none were on vitamin D supplementation. Only 35.6% (26/73) were normocalcaemic (<2.74mmol/L).Hypercalcaemiapresented in the 1st and 2nd weeks of life in 81.0% (17/21) of patients. Median creatinine during thehypercalcaemia was 86µmol/L (range 52-217) compared to 73µmol/L (range 43-121) at 2 weeks of life. Hypercalcaemic patients took a median of 42 days (mean 56.78, range 12-138) to achieve their lowest creatinine in 3 months, compared to normocalcaemic patients with a median of 49 days (mean 47.37, range 8-122). Table 1: Annual cases of hypercalcaemia in PUV patients
In 2015 100% (4/4) of patients with sufficient data available aquired hyper-calcaemia, notably higher than previous years (table 1). This may coincide with recent increased use of vitamin D supplementation antenatally. Long term consequences of patients with PUV and hypercalcaemia included: 2/21 hypertension, 1/21 nephrocalcinosis, 0/21 nephrolithiasis, 3/21 had CKD stage 2 and 1/21 had CKD stage 3.
CONCLUSION: There is an association between infants with PUV and hypercalcaemia which supports previous limited evidence. The incidence increased significantly in 2015. Hypercalcaemia is most likely to present in the first 2 weeks of life along with an associated risein plasma creatinine, which takes longer toreach a nadir (at3 months of life).The effect of hypercalcaemia on these infants is as yet unknown, although there is evidence of hypertension, nephrocalcinosis and CKD.Longer follow up is needed to quantify these possible complications. Measuring adjusted calcium is therefore recommended in this populationto identify any hypercalcaemia, especially during the first 2 weeks of life.