Editing Stones: Epidemiology and Pathogenesis (section)

=== Oxalate ===
* '''Only 6-14% of ingested oxalate is absorbed (compared to 30-40% of ingested calcium is absorbed)'''
** '''Oxalate absorption occurs throughout the intestinal tract, with about half or more occurring in the small intestine and half in the colon'''
** '''Factors that influence oxalate absorption (2):'''
**# '''Oxalate-degrading bacteria'''
**#* '''Oxalobacter formigenes use oxalate as an energy source and consequently reduce intestinal oxalate absorption'''
**# '''Presence of oxalate-binding cations such as calcium or magnesium'''
**#* '''Co-ingestion of calcium, magnesium, and oxalate-containing foods leads to formation of calcium oxalate complexes, which limits the availability of free oxalate ion for absorption'''
* '''Absorbed oxalate is nearly completely excreted in the urine'''
** '''Urinary oxalate is derived from both endogenous production in the liver''' (from ascorbic acid and glycine) '''and dietary sources.'''
*** '''On average, half of urinary oxalate is derived from the diet, with the precise amount depending on the relative amount of ingested calcium and oxalate'''
** It is estimated that between 86-98% of oxalate is ultrafilterable. However, '''renal tubular handling of oxalate has not been clearly defined, although both secretion and reabsorption have been suspected.'''