title: Major factors modulating the serum oxalic acid level in hemodialysis patients.
abstract: Ascorbic acid overload and vitamin B6 deficiency have been implicated in the development of hyperoxalemia in dialysis patients, but there is still disagreement about this. Hemodialysis patients who are exposed long-term hyperoxalemia may develop secondary oxalosis with an increased risk of cardiac, vascular, and bone disease, and thus may benefit from maintaining a low serum oxalic acid level. In 452 hemodialysis patients, the serum level of oxalic acid was 47.2 +/- 22.9 micromol /l before and 16.9 +/- 10.5 micromol/l after a 4-hour dialysis session, while the ascorbic acid levels were 39.0 +/- 92.7 micromol/l and 6.5 +/- 18.6 micromol/l, the glycolic acid levels were 7.3 +/- 10.1 micromol/l and 0.6 +/- 2.3 micromol/l, and the citric acid levels were 141.3 +/- 54.7 micromol/l and 117.6 +/- 37.2 micromol/l, respectively. Most patients (65.3 percent) had low serum ascorbic acid levels (less than 10 micromol/l) before hemodialysis. The serum level of oxalic acid [Ox] showed a significant positive correlation with the levels of ascorbic acid [AA], glycolic acid [Gly], and creatinine [Cre]: [Ox] = 21.711 + 0.181 x [AA] + 0.174 x [Gly] + 0.171 x [Cre], (all micromol/l, p less than 0.05). In 124 dialysis patients, the 4-pyridoxic acid level was 8.9 +/- 19.6 micromol /l before and 3.9 +/- 8.8 micromol/l after dialysis, and it was not correlated with oxalic acid or glycolic acid. Most dialysis patients (65.3 percent) had low serum levels of ascorbic acid, but a subgroup of patients (12 percent) had high serum ascorbic acid levels (more than 100 micromol/l) associated with hyperoxalemia (88.2 +/- 24.5 micromol/l). High-dose vitamin C supplementation may aggravate hyperoxalemia in hemodialysis patients, so attention should be paid to avoiding this risk.
authors.affiliation: Department of Urology, University of the Ryukyus, Okinawa, Japan 903-0215. ogawa@med.u-ryukyu.ac.jp
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Ogawa
authors.forename: Noriko
authors.initials: N
authors.lastname: Machida
authors.forename: Masahide
authors.initials: M
authors.lastname: Jahana
authors.forename: Munehisa
authors.initials: M
authors.lastname: Gakiya
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Chinen
authors.forename: Masami
authors.initials: M
authors.lastname: Oda
authors.forename: Makoto
authors.initials: M
authors.lastname: Morozumi
authors.forename: Kimio
authors.initials: K
authors.lastname: Sugaya
mesh_terms: D000368:Aged; D001205:Ascorbic Acid / Q000097:blood / Q000378:metabolism; D019343:Citric Acid / Q000097:blood; D003404:Creatinine / Q000097:blood; D005260:Female; D006016:Glycolates / Q000097:blood; D006801:Humans; D007676:Kidney Failure, Chronic / Q000628:therapy; D008297:Male; D008875:Middle Aged; D019815:Oxalic Acid / Q000097:blood*; D011735:Pyridoxic Acid / Q000097:blood; D006435:Renal Dialysis / Q000379:methods*; D012306:Risk; D013997:Time Factors; D025101:Vitamin B 6 / Q000378:metabolism
chemical_list: D006016:Glycolates; C031149:glycolic acid; D019343:Citric Acid; D011735:Pyridoxic Acid; D025101:Vitamin B 6; D019815:Oxalic Acid; D003404:Creatinine; D001205:Ascorbic Acid