Types Of Crystals In Urine

Types Of Crystals In Urine Overview

  • There are several distinct compounds in urine. These substances have the potential to crystallise into salt under certain conditions. It is known as crystalluria.
  • Crystals have a distinctive refractile look.
  • An urinalysis, a test that examines several chemicals in the urine, frequently includes a crystal in urine test.
  • The discovery of the majority of crystals is not very significant, since normal urine includes a wide variety of substances from which crystals might form.
  • This means that even in animals with no signs of a urinary illness, such as blockage and/or urolithiasis, crystals can be found in their urine.
  • However, under specific conditions, certain crystals may be pathologically significant. When urinary tract calculi (stones) are detected, fresh urine should be examined for crystals.

Types of Crystals in Urine

  • A variety of crystal types can be found in urine. While some are thought to be odd crystals, some are considered typical crystals.
  • Normal Crystals that are considered normal include those made of uric acid, calcium oxalate, hippuric acid, calcium phosphate, triple phosphate (struvite), calcium carbonate, ammonium biurate, and others.
  • Abnormal crystals:Crystals that shouldn’t be there include crystals of bilirubin, cholesterol, cystine, leucine, tyrosine, acyclovir, and indinavir.

Struvite crystals

  • Struvite crystals, commonly referred to as triple phosphate or magnesium ammonium phosphate, often take the form of colourless, prism-like, three-dimensional crystals, or “coffin lids.”
  • They may easily be seen at low magnification since they are often big.
  • The most prevalent kinds of struvite crystals may be seen in dog and cat urine. They are frequently observed in the urine of clinically healthy people.
  • Despite the fact that they may be detected in urine of any pH, neutral to alkaline urine is where they are most likely to occur.
  • Urease-positive bacteria urinary tract infection may promote struvite crystalluria via elevating free ammonia and rising urine pH. (and urolithiasis).

Cystine crystals

  • Their six sides help to identify them. When discovered in urine, the crystals are frequently hexagonal in form and occasionally white.
  • They frequently gather in layers and may have equal or uneven sides.
  • Acidic urine is more conducive to their production.
  • These small to moderate crystals ought to be slightly discernible at low magnification.
  • They are 30% v/v soluble in hydrochloric acid (different crystals of uric acid that they could resemble).
  • Cystine excretion in the urine is an uncommon congenital metabolic condition called cystinuria, which is when they are present.
  • Blood in the urine, nausea, vomiting, and back or groyne discomfort are a few symptoms that might occur.

Cholesterol crystals

  • They resemble long, transparent rectangles with rounded edges.
  • They are more likely to manifest themselves following the cooling of the urine sample.
  • Both neutral and acidic urine can include cholesterol crystals.
  • They are soluble in ether, ethanol, and chloroform but insoluble in acids and alkalis.
  • They are rarely found, unless there is severe kidney disease or a ruptured lymphatic artery into the renal pelvis.
  • They could be brought on by renal tubular disease, which, if left unchecked, might result in renal failure.
  • Alkali therapy may be used as a kind of treatment for long-term metabolic disorders such as renal tubular disease.

Tyrosine crystals

  • They have a golden or black colour and resemble clusters of needles.
  • In ethanol, ether, and acetone, they cannot be dissolved.
  • There’s a chance that metabolic illnesses caused them, such as liver disease or tyrosinemia, and they are frequently detected in urine that is acidic.
  • Tyrosinemia can cause vomiting, diarrhoea, bloody stools, fever, and difficulties gaining weight.
  • Exercise, maintaining a nutritious diet, and using drugs that might perhaps control diabetes, high blood pressure, and high cholesterol are all part of the treatment.

Bilirubin crystals

  • Bilirubin crystals are often very tiny, needle-like, granular, and yellow in colour.
  • They frequently precipitate on top of other urine-derived components.
  • They are often tiny crystals that can only be seen under close scrutiny (unless there are large aggregates of crystals).
  • It may be a sign of liver illness or impaired liver function if there are high amounts of bilirubin or bilirubin crystals in the urine.
  • Other signs and symptoms might include fever, jaundice, vomiting, discomfort, and nausea.
  • The underlying reason determines the course of treatment. Particularly in situations of cirrhosis, it is possible to change how much protein is absorbed from food by medicine.

Calcium carbonate crystals

  • Crystals of calcium carbonate come in a variety of sizes and often take the form of sizable spheroids with radial striations.
  • They might alternatively be described as more compact, ovoid to spherical crystals.
  • They range in colour from colourless to yellow-brown, and when they are present in large quantities, they can give the urine a brownish tint.

Calcium oxalate crystals

  • Typically, calcium oxalate dihydrate crystals are colourless squares with crossing lines connecting their corners (resembling an envelope).
  • Since they may exist in urine with any pH, they are commonly observed.
  • These crystals range in size from extremely microscopic to fairly large, which may be seen at low magnification (requiring high magnification to visualize).
  • Large quantities of small oxalates may occasionally look amorphous if not seen under a strong microscope.
  • They may be an indication of urinary tract calculi when discovered in recently discharged urine.

Ammonium Biurate crystals

  • These gems are brown spheres with pointed thorns.
  • They somewhat resemble bugs at first sight.
  • Although they can be detected in regular pee as well, they are frequently found in alkaline urine.
  • Ammonium biurate crystals can occasionally be seen in ancient or poorly maintained urine samples.
  • Thus, if these crystals are present, it may be advised to obtain another urine sample.

Leucine crystals

  • These crystals have concentric rings that resemble a tree trunk and are yellow-brown discs.
  • Normally, leucine crystals don’t appear in the urine of healthy people. Urine that is acidic contains them.
  • They frequently indicate serious liver disease. Swelling in the abdomen, nausea, vomiting, confusion, and malaise are possible additional symptoms.
  • Improving liver health and function are immediate treatment goals. This will involve taking drugs to lower the danger of bleeding and to lessen swelling brought on by an excess of fluid.

Amorphous Crystals

  • At the light microscopic scale, “amorphous” crystals are an aggregation of finely granular material that lack any discernible structure.
  • They could contain phosphates, urates, or xanthine.
  • They resemble microorganisms and are often little crystals that can only be seen at strong magnification (unless there are many of them).
  • The discovery of amorphous crystals cannot be used as the basis for any particular clinical interpretation. Gram-staining can be used to identify small amorphous crystals from bacterial cocci, which can occasionally be mistaken for one another.
  • Amorphous crystals can also mimic dying cells or crystals.

Other crystals found in urine

  • On rare occasions, sulfonamide crystals are discovered in the urine of patients receiving sulphonamide therapy. They can result in haematuria and other problems when they are deposited in the urinary system.
  • HIV is treated with the drug indinavir. It may result in the growth of urine crystals. Indinavir crystals can have the shapes of fans, square plates, or starbursts.
  • The crystals of uric acid are yellow or pink-brown.
  • Calculi can occasionally be used to find them.

Detecting and Reporting Crystals in Urine

  • This evaluation is based on low power images of big crystals, such as calcium carbonate and struvite (10x objective).
  • The high power (40x) objective is used for tiny crystals, such as amorphous calcium oxalate dihydrate.
  • In urine, crystals can be classified as few, moderate, or numerous.

Factors Influencing the Types and Numbers of Urinary Crystals

In vivo factors

  • crystallogenic material concentration and solubility in the specimen.
  • Urine pH
  • Diet
  • Excretion of medicinal drugs and diagnostic imaging

In vitro factors

  • Temperature (solubility decreases with temperature)
  • Evaporation (increases solute concentration)
  • Urine pH (changes with standing and bacterial overgrowth)


  1. Cheesbrough M. (2006). District Laboratory Practice Tropical Countries, 2nd Edition. Cambridge University Press.
  2. http://www.eclinpath.com/urinalysis/crystals/
  3. https://medlineplus.gov/lab-tests/crystals-in-urine/
  4. https://www.healthline.com/health/urine-crystals#types
  5. http://www.eclinpath.com/atlas/urinalysis/
  6. https://www.labce.com/spg961161_table_normal_crystals.aspx
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