Identification of Calcium Oxalate Monohydrate Crystals by X-ray Diffraction in Urine of Ethylene Glycol-Intoxicated Dogs

Abstract

Abstract. Urine sediments of dogs with experimentally induced ethylene glycol poisoning were examined by light microscopy and X-ray diffraction. Massive calcium oxalate crystalluria was observed in all poisoned dogs. By light microscopy, the frequency with which six-sided hippurate-like prisms and envelope forms of calcium oxalate dihydrate occurred was approximately equal. The hippurate-like crystals were shown to be calcium oxalate monohydrate by X-ray diffractometry.Ethylene glycol (antifreeze) toxicosis is commonly observed in dogs and cats.23 Ethylene glycol is metabolized to glycoaldehyde, glycolic acid, glyoxylic acid, oxalic acid, and hippuric acid, which result in acidosis, cytotoxicosis, and subsequent renal failure. I The diagnosis often depends on laboratory findings such as metabolic acidosis, a large anion and osmolal gap, and ~rystalluria.~ The presence of calcium oxalate crystalluria is frequently cited as a useful diagnostic aid in ethylene glycol poisoning in people and animals, although crystals are not seen in every ~a s e .~,~~ The type of calcium oxalate crystal referred to most commonly in standard texts on urinalysis is the octahedral calcium oxalate dihydrate ("envelope" or "Maltese cross" form).2 Less frequently reported is the "hempseed"-shaped calcium oxalate monohydrate.".22 In addition, crystals very similar to published photographs and diagrams of six-sided prismatic hippurate crystals have been reported in p e~p l e ' .~.~. '~,~' and a r~i m a l s . '~.~~ In a retrospective study of ethylene glycol toxicosis in 50 dogs and cats, calcium oxalate dihydrate crystals (envelope forms) were observed in the urine of only 18% of the dogs and cats. Hippurate-like crystalluria was more frequently observed (44% of dogs and 18% of cats).23 Although hippuric acid is excreted in the urine of ethylene glycol-poisoned dogs," it is thought to be the least significant metabolite q~antitatively,'~ and probably could not account for the massive hippurate-like crystalluria which is commonly observed. In order to accurately identify these hippurate-like crystals, urine 6 sediments of eight dogs with experimentally induced ethylene glycol poisoning were examined by light microscopy and X-ray diffraction. X-ray diffraction was used because of its ability to absolutely identify crystals with a certainty, since the X-ray diffraction pattern of a compound is unique. lo, l9 X-ray diffraction involves the passage of a monochromatic beam of X-rays through the crystalline substance. Diffraction of the Xray beam by the planes of atoms is observed as a line or peak. The angular spacings of the lines are then used to calculate the distance (d-spacing) between the planes of atoms in the crystal. To identify crystals, the unknown pattern (d-spacing) is then compared with standard X-ray patterns of known substances." Materials and MethodsEight mature, healthy mixed-breed dogs were fasted for 24 hours, pretreated with chlorpromazine ( 1 mg/kg body weight) to prevent vomiting, and fed 10 ml/kg body weight of 95% ethyle...

Inhibition of canine and feline alcohol dehydrogenase activity by fomepizole

“…The minimal lethal dose of EG is lower in cats 35 than in dogs. 37 However, our findings of lower V max of feline ADH suggest that hepatic ADH metabolism of EG is less efficient in cats than in dogs. 10,20 Finally, calcium oxalate crystalluria may be observed as early as 3 hours after EG ingestion in cats, 20 compared with 6 hours after ingestion in dogs.…”

Calcium oxalate crystals in fetal bovine serum: Implications for cell culture, phagocytosis and biomineralization studies in vitro

“…Energy‐dispersive X‐ray microanalysis was performed using an Oxford INCA microanalysis system (Model D‐7200) with its installed software INCA Microanalysis Suite (Version 4.04). For powder X‐ray diffraction analysis, the crystalline material was collected as described above, and the crystals were re‐suspended in absolute ethanol and pipetted onto a glass coverslip and analyzed as described previously [Thrall et al, 1985]. Briefly, X‐ray diffraction analysis was performed with Cu Kα X‐rays on a Philips powder X‐ray diffractometer (Model PW 1710).…”

Ethylene Glycol

“…43,55 COM crystals are variably sized, clear, six-sided prisms ( Figure 47-1). [61][62][63][64] The detection of calcium oxalate crystalluria, particularly the monohydrate form, provides strong supporting evidence for the diagnosis of EG poisoning. 26,29 Dumbbell or sheaf-shaped crystals are observed infrequently.…”