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Review
. 2022 Nov;36(11):e24707.
doi: 10.1002/jcla.24707. Epub 2022 Sep 26.

Differential identification of urine crystals with morphologic characteristics and solubility test

A-Jin Lee  1 , Eun-Hyung Yoo  1 , Young-Cheol Bae  2 , Sang Bong Jung  3 , Chang-Ho Jeon  1
Affiliations
Review

Differential identification of urine crystals with morphologic characteristics and solubility test

A-Jin Lee et al. J Clin Lab Anal. 2022 Nov.

Abstract

Background: Urinary crystals are the most diverse forms of urine sediments. Reference images for typical urinary crystals are common, however, but images for interpreting atypical urinary crystals are very rare. The authors reviewed various forms and solubility tests of urine crystals to interpret atypical crystals found in clinical specimens.

Methods: We reviewed textbooks on urinary crystals and articles published in PubMed. Some atypical crystals were confirmed using a solubility test.

Results: The classification, shape, chemical structure, and solubility of the crystals were summarized. In the solubility test, some crystals showed different results; therefore, a new solubility test was proposed based on the literature review. We presented various types of calcium oxalates.

Conclusions: These review articles will be helpful in the examination of atypical crystals found in clinical specimens. The solubility test requires additional studies to discriminate the inconsistent results between the authors.

Keywords: classification; crystal; crystalluria; solubility test; urine.

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Conflict of interest statement

There is no conflict of disclosure.

Figures

FIGURE 1
FIGURE 1
Various shapes of calcium oxalate crystals: (A) dumbbell shape (x400). (B) red blood cell shape (x400). (C) narrow hexagons (x100). (D) club shape or rosette forming crystals (x400). (E) bipyramidal shape (x400) (F) dodecahedral shape (x400).
FIGURE 2
FIGURE 2
Two calcium phosphate crystals: (A) amorphous calcium phosphate with a large plate (x100). (B) brushite, stick shape calcium phosphate dihydrate (x100).
FIGURE 3
FIGURE 3
Two triple phosphate crystals: (A) coffin lid shape (x200). (B) fernlike X‐shape (x200).
FIGURE 4
FIGURE 4
Various shapes of uric acid crystals: (A) amorphous urate (x100). (B) sodium urate showing aggregation of needle shape crystals (x100). (C) ammonium biurate (x400). (D) uric acid monohydrate (x400). (E) uric acid dihydrate (x400).
FIGURE 5
FIGURE 5
Dihydroxyadenine crystals showing central density with radiating spicules (x400).
FIGURE 6
FIGURE 6
Cystine crystals showing colorless, refractile, and hexagonal plates (x400).
FIGURE 7
FIGURE 7
Differentiation of urine crystals by solubility test: (A) Crystals in urine, (B) insoluble crystals with 10% KOH, (C) the sharp‐pointed rectangular crystals were dissolved in 30% acetic acid, (D) bipyramidal crystals were dissolved in 30% acetic acid (all x400).
See this image and copyright information in PMC

References

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