Calciumoxalat

Calcium oxalate is an inorganic salt with the formula CaC2O4. It occurs in two common hydrates: the dihydrate CaC2O4·2H2O (weddellite) and the monohydrate CaC2O4·H2O (whewellite). In nature it forms crystals in many plants (often as needle-like raphides) and can be a metabolic byproduct excreted in urine in humans.

Calcium oxalate is highly insoluble in water and only slightly soluble in acids. It can precipitate from urine when calcium and oxalate concentrations are high, a process that underlies many kidney stones. Calcium oxalate stones are among the most common types of urinary tract calculi.

Biochemically, oxalate is produced endogenously and also obtained from the diet. Dietary calcium can bind oxalate in the gut, reducing its intestinal absorption. Management of calcium oxalate stones typically emphasizes high fluid intake, restriction of high-oxalate foods (such as spinach, rhubarb, nuts, and chocolate), and, in some patients, medications that reduce urinary calcium or increase citrate to inhibit crystallization.

In plants, calcium oxalate crystals can contribute to tissue rigidity and serve as a defense against herbivores. In humans, the primary clinical relevance is its role in stone formation; the compound is generally not highly toxic, with health concerns mainly arising from stone-related symptoms and complications.