Crystalluria

Crystalluria is often present in routine urinalysis. The precipitation of crystals occurs in supersaturated urine. "Non-specific crystalluria" may be caused by food intake, pH and/or temperature changes of the urine, specially when urine is not analysed immediately. This randomly observed "non-specific crystalluria" is of no clinical value. In contrast, "specific" crystalluria can be associated with diseases such as nephrolithiasis, primary hyperoxaluria or ethylene glycol poisoning. Some drugs are excreted as crystals and may cause heavy crystalluria leading to kidney injury; this is the case of retroviral drugs and some antibiotics used in clinical practice. In these situations the diagnosis can be made by urinalysis and therapy be adapted accordingly. Important for the analysis of crystalluria is the correct handling of the fresh urine, knowledge of urinary pH and, of course, training in microscopic techniques.