<prompt> Birefringent crystal in urine is seen withCalcium oxalate stonesUric acid stonesStruvite stonesNone  <response>: There are two types of calcium oxalate crystals, the dihydrate or Wedellite and the monohydrate orWhewellite, which are frequently found together inthe same sample. The former have mostly a typical bipyramidal shape, while the latter are more pleiomor- phichic , 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 Table 1. 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 stone formers, in patients with hyperoxaluria, or after ethylene glycol poisoning see Crystalluria and acute renal failure. Refer robbins 9e p951 