Fasting versus 24-h urine pH in the evaluation of nephrolithiasis

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

An abnormal urinary pH (UpH) represents an important risk factor for nephrolithiasis. In some stone formers, a fasting urine specimen is obtained instead of a 24-h urine collection for stone risk evaluation. We examined the relationship between 24-h and fasting UpH in non-stone forming individuals and stone formers with various etiologies and a wide range of urine pH to test the validity of fasting UpH. Data from 159 subjects was examined in this retrospective study. We included non-stone forming subjects and stone formers with hypercalciuria, distal renal tubular acidosis, idiopathic uric acid nephrolithiasis, or chronic diarrhea. Participants collected a 24-h urine followed by a 2-h fasting urine. For the entire cohort, a significant correlation was seen between fasting and 24-h UpH (r 2 = 0.49, p < 0.001). Fasting pH was significantly higher than 24-h UpH for the entire cohort (6.02 ± 0.63 vs. 5.89 ± 0.51; p < 0.001), and in the subgroups of non-stone formers and stone formers with hypercalciuria or distal renal tubular acidosis. Fasting UpH was >0.2 pH units different from 24-h UpH in 58% of participants. The difference between fasting and 24-h UpH did not correlate with net gastrointestinal alkali absorption or urine sulfate, suggesting that dietary factors alone cannot explain this difference in UpH. Fasting urine pH correlates moderately with 24-h urine pH in a large cohort of individuals. Significant variability between these two parameters is seen in individual patients, emphasizing the cardinal role of 24-h urine collection for evaluating UpH in nephrolithiasis.

Original languageEnglish (US)
Pages (from-to)367-372
Number of pages6
JournalUrological Research
Volume39
Issue number5
DOIs
StatePublished - Oct 2011

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Nephrolithiasis
Fasting
Urine
Urine Specimen Collection
Renal Tubular Acidosis
Hypercalciuria
Alkalies
Uric Acid
Sulfates
Diarrhea
Retrospective Studies

Keywords

  • Nephrolithiasis
  • Urine pH

ASJC Scopus subject areas

  • Urology

Cite this

Fasting versus 24-h urine pH in the evaluation of nephrolithiasis. / Capolongo, Giovanna; Sakhaee, Khashayar; Pak, Charles Y C; Maalouf, Naim M.

In: Urological Research, Vol. 39, No. 5, 10.2011, p. 367-372.

Research output: Contribution to journalArticle

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