Study of urinary acidification in patients with idiopathic hypocitraturia

Abstract

Hypocitraturia (HCit) is one of the most remarkable features of renal tubular acidosis, but an acidification defect is not seen in the majority of hypocitraturic patients, whose disease is denoted idiopathic hypocitraturia. In order to assess the integrity of urinary acidification mechanisms in hypocitraturic idiopathic calcium stone formers, we studied two groups of patients, hypocitraturic (HCit, N = 21, 39.5 ± 11.5 years, 11 females and 10 males) and normocitraturic (NCit, N = 23, 40.2 ± 11.7 years, 16 females and 7 males) subjects, during a short ammonium chloride loading test lasting 8 h. During the baseline period HCit patients showed significantly higher levels of titratable acid (TA). After the administration of ammonium chloride, mean urinary pH (3rd to 8th hour) and TA and ammonium excretion did not differ significantly between groups. Conversely, during the first hour mean urinary pH was lower and TA and ammonium excretion was higher in HCit. The enhanced TA excretion by HCit during the baseline period and during the first hour suggests that the phosphate buffer mechanism is activated. The earlier response in ammonium excretion by HCit further supports other evidence that acidification mechanisms react promptly. The present results suggest that in the course of lithiasic disease, hypocitraturia coexists with subtle changes in the excretion of hydrogen ions in basal situations.

Hypocitraturia: a risk factor for reduced bone mineral density in idiopathic hypercalciuria?

“…Therefore, a reduction in serum pH and bicarbonate in patients with HC suggests that the primary factor involved could be a deficiency in intracellular acidification, which is generally present in patients with IH but is more severe in those with HC, as suggested by Araffljo and Rebelo [26].…”

Longitudinal study of bone mineral density in children with idiopathic hypercalciuria

“…These findings led the authors to suggest that the presence of a certain degree of intracellular acidosis and/or an increased production of prostaglandin E2 (PGE2) is involved in the mechanism of bone mass reduction in these patients [1]. Araujo and Rebelo [49] also suggested that the primary factor involved in bone mass reduction in those patients could be a deficiency in intracellular acidification, which is generally present in patients with IH, but is more severe in those with hypocitraturia.…”

Signification of distal urinary acidification defects in hypocitraturic patients

“…Acquired dRTA frequently develops as a consequence of Gougerot-Sjögren syndrome [8] and other autoimmune diseases [9, 10]. Very few studies have evaluated the utility of screening for a urinary acidification defects in non-acidotic patients with concomitant hypocitraturia, recurrent nephrolithiasis [11, 12], and/or bone demineralization [13, 14]. In the present study, we retrospectively analyzed data from patients with low citrate excretion and nephrolithiasis, nephrocalcinosis, and/or bone demineralization.…”