Types Of Crystals In Urine Overview

• There are several distinct compounds in the urine. These substances have the potential to crystallize into salt under certain conditions. It is known as crystalluria.
• Crystals have a distinctive refractile look.
• A urinalysis is a test that examines several chemicals in the urine and frequently includes a crystal in the 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.
• Similarly, the 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 considered odd crystals, others are considered typical.
• 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, cysteine, leucine, tyrosine, acyclovir, and indinavir.

Struvite Crystals

• Struvite crystals commonly referred to as triple phosphate or magnesium ammonium phosphate, often take the form of colorless, prism-like, three-dimensional crystals or “coffin lids.”
• They may be easily seen at low magnification since they are often bigger in size.
• 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 the urine of any pH, neutral to alkaline urine is where they are most likely to occur.
• Urease-positive bacteria which cause urinary tract infection may promote struvite crystalluria by elevating free ammonia and increasing urine pH. (and urolithiasis).

Cystine Crystals

• The cysteine crystals have six sides, a unique feature to identify them. The crystals are frequently hexagonal in shape and occasionally white in color.
• They frequently gather in layers and may have equal or uneven sides.
• Acidic urine is more conducive to the production of cysteine crystals.
• These small to moderate-sized 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.
• Blood in the urine, nausea, vomiting, and back or groin 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 an individual has severe kidney disease or a ruptured lymphatic artery in 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 a treatment option for long-term metabolic disorders such as renal tubular disease.

Tyrosine Crystals

• They have a golden or black color and resemble clusters of needles.
• In ethanol, ether, and acetone, they cannot be dissolved.
• There is a chance that metabolic illnesses caused by them, such as liver disease or tyrosinemia, are frequently detected in urine that is acidic.
• Tyrosinemia can cause vomiting, diarrhea, bloody stools, fever, and difficulty gaining weight.
• Exercise, maintaining a nutritious diet, and using drugs that might 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 color.
• 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

• Calcium carbonate crystals come in various 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 color from colorless 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 colorless 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 indicate 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 also be detected in regular pee, 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.
• Usually, leucine crystals don’t appear in the urine of healthy people. Urine that is acidic contains them.
• They frequently indicate severe 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 lacks 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).
• 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.

You may also like to read: Human Digestive System

Other Crystals in the 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 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)

References

1. Crystals in Urine: clevelandclinic.org
2. Crystals in the Urine: What You Need to Know: healthline.com