Abstract

A by the enzyme citrate synthase.1, 2 Citrate is thought to be freely filterable at the
glomerulurs, in humans, 65 to 90% of the filtered citrate is reabsorbed and 10 to 35% is
excreted in the urine as a byproduct of oxidative pathways in the body.3, 4 It is known to
inhibit precipitation of calcium oxalate and phosphate and growth of their crystals5.
In 1990 Pak has defined normal 24 hour urinary citrates as more than 320 mg for both
genders6. Hypocitraturia is defined as urinary citrate excretion lower than 1.67 mmol
(320mg) per day. However, there are some reports of low urinary citrate output in stone
formers (SF) and renal failure as compared with healthy subjects7-9, while other studies found
no differences10,11.
Prevalence of hypocitraturia varies widely from 8% to 68.3% in patients with renal
stones.6 Furthermore; there are some differences in the range of 24-hour urinary citrate
excretion in normal subjects.10, 12
Urinary pH is also an important factor in stone risk, with higher values favoring
calcium phosphate stones and lower ones uric acid stones13. Although final urine pH is
associated with acid load, it is also influenced by ammonium excretion and the ability of
the distal tubule to acidify the collecting duct. Overall factors that influence urine pH and
citrate are similar, but not identical.
Various studies have evaluated the citrate levels and have conflicted results. Most of the
studies have been done in stone former patients and very limited studies have been done
in normal Indian population. In this study we intend to find out the normal range of citrate
excretion in normal subjects and its relation with various factors.