Question: Describe the morphologic features of the calcium oxalate urine crystals that may be found in the urine of individuals who ingested ethylene glycol.
Answer: The cited reference notes “Examination of the urine sediment by means of light microscopy reveals calcium oxalate monohydrate crystals.” These may have a variety of morphologies including “narrow rectangles with pointed ends” and “dumbbell shaped crystals”. The authors point out that “Under polarized light, crystals [are] positively birefringent;….blue when parallel to the light and yellow when perpendicular to the light”. (Hanouneh M and Chen TK. Calcium oxalate crystals in ethylene glycol toxicity. 2017 NEJM 377(15):1467)