Birefringent crystal in urine is seen with

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 9/e p951