Urinalysis, Complete With Microscopic Examination – 003772

MICROSCOPY:

Crystalluria is frequently observed in urine specimens stored at room temperature or refrigerated. Such crystals are diagnostically useful when observed in warm, fresh urine by a physician evaluating microhematuria, nephrolithiasis, or toxin ingestion.

In abundance, calcium oxalate and/or hippurate crystals may suggest ethylene glycol ingestion (especially if known to be accompanied by neurological abnormalities, appearance of drunkenness, hypertension, and a high anion gap acidosis). Large numbers of calcium oxalate crystals occur, as well, with acute renal failure following methoxyflurane anesthesia. Urine is usually supersaturated in calcium oxalate, often in calcium phosphate, and acid urine is often saturated in uric acid. Yet crystalluria is uncommon (in warm, fresh urine) because of the normal presence of crystal inhibitors, the lack of available nidus, and the time factor. When properly observed in fresh urine, crystals may provide a clue to the composition of renal stones even not yet passed, the nidus for such stones, or, as such, have been associated with microhematuria.