Crystalluria Calcium oxalate crystalluria 2019-07-05T19:06:11Z There are two types of calcium oxalate crystals, the dihydrate (or Wedellite) and the monohydrate (orWhewellite), which are frequently found together in the same sample. The former have mostly a typical bipyramidal shape, while the latter are more pleiomorphic, although the ovoid shape is the most frequent. Bipyramidal crystals are birefringent only when large or in aggregates, but even then birefringence is usually not intense. The monohydrates, however, are always strongly birefringent. Calcium oxalate may be found in normal subjects, often as a consequence of ingestion of foods like chocolate, beet-root, peanuts, rhubarb, spinach, etc., in stoneformers, in patients with hyperoxaluria, or after ethylene glycol poisoning. The presence of calcium oxalate crystals in the urine.