Long-term outcome in children with primary distal renal tubular acidosis

To evaluate complications in adequately treated children with distal renal tubular acidosis (RTA) and to identify factors influencing their development.

Records of patients with primary distal RTA followed for 2 or more years at this hospital were reviewed. Case records were examined for age at onset of symptoms and at initiation of treatment, treatment details, follow-up and complications. Height, weight and growth velocity were expressed as standard deviation score (SDS) during different periods of follow-up. Regression analysis was performed to evaluate factors influencing increase in height and weight SDS. P value of less than 0.05 was considered significant.

Of 18 patients (eleven boys), the diagnosis was established at the median (range) age of 6 yr (1.5-13 yr). These patients were followed up for a median (range) period of 4 yr (2-18.5 yr). Short stature (height SDS <-2) was noted in all patients at the time of diagnosis with median (range) height SDS of -5.2(-7.5 - -0.4). All patients had failure to thrive with median (range) weight SDS of -3(-5.7 - -1.5). Height SDS increased by median (range) of 2 (1.2-5.5) to become -2.7(-4.8 - -1.1) at last follow-up. Weight SDS increased by median (range) of 0.9 (-0.6 - 2.8) to become -2.4 (-4 - -0.5). Median (range) growth velocity SDS decreased from 3 (1-16) during first year of treatment to 1(-0.3 - 7) at four years with an increase in mean height SDS by 1.3 during the first two years of treatment. Height SDS at last follow-up was not influenced by the age at initiation of treatment, follow-up duration, initial height SDS or severity of acidosis at diagnosis. Increase in height SDS correlated negatively with base excess and height SDS at diagnosis, and positively with follow-up duration on univariate analyses. Initial height SDS was the only factor that influenced increase in height SDS on multivariate analyses. Increase in weight SDS was negatively correlated with base excess and initial weight SDS with significant association with initial weight SDS, on multivariate analyses. All patients had rickets at the time of diagnosis with pathological fractures in four. Rickets resolved without treatment with vitamin D in seventeen patients after a median (range) period of 4 mo (1-12 mo). Eight patients (44.4%) had nephrocalcinosis at diagnosis. Twenty-four hour urine calcium excretion was higher in those with nephrocalcinosis (p = 0.01). Creatinine clearance remained normal in all except one who progressed to renal failure.

There is a need for early diagnosis, appropriate treatment and regular follow-up of patients with distal RTA for improving outcome.