Urine Crystals – Types, Shapes, Color, Causes

  • Urine contains a large number of different chemicals. Under some circumstances, these chemicals may solidify into salt crystals. This is called crystalluria. Crystals can be found in the urine of healthy individuals. They may be caused by minor issues like a slight excess of protein or vitamin C. Many types of urine crystals are relatively harmless.
  • Unless large enough stones form, urine crystals usually cause few indications and symptoms. When this happens, the stone may pass spontaneously out of the body or medical intervention may be required to assist in the removal of the stone.

Urine Crystals

  • Uric acid crystals occur in acidic urine, which has a pH of less than 5.5. Because uric acid is soluble in alkaline urine, urate crystals do not form. Urinary alkalinization in individuals at risk for acute uric acid nephropathy is justified by the inability of uric acid to crystallise at urine pH > 7.0. Hematuria, glycosuria, and proteinuria are not commonly linked with uric acid crystalluria.
  • Although crystals can be visible under a microscope in specific clinical circumstances, such as kidney stone disease or acute crystal nephropathy, this does not mean that the crystals were present in the urinary system.
  • After micturition, crystals might form again. Variations in temperature, such as those caused by storing urine at ambient temperature or in the refrigerator, or changes in urinary pH, such as those caused by infection with urea-splitting organisms, are the most prevalent causes of crystal precipitation following micturition.

Types of urine crystals

Urate Urine Crystals

Urine Crystals
  • When uric acid levels in the urine are too high and/or the urine is too acidic (pH level below 5.5) on a frequent basis, uric acid stones occur.
  • Shapes: Urate crystals have pointy ends and are shaped like needles or toothpicks. Urate crystals are yellow when aligned parallel to the axis of the red compensator and blue when oriented across the direction of polarisation in polarising light microscopy.
  • Colour: Uric acid kidney stones are often red–orange–brown in Color, though uric acid crystals are Colorless.
  • Causes: A high uric acid level is usually caused by your kidneys failing to remove uric acid effectively. Rich foods, being overweight, having diabetes, taking some diuretics (also known as water pills), and drinking too much alcohol are all factors that can slow down the clearance of uric acid.

Cystine Urine Crystals

Urine Crystals
  • An uncommon condition known as “cystinuria” causes cystine stones. A natural chemical called “cystine” leaks into your urine as a result of the condition. Kidney stones can occur when there is too much cystine in the urine. Stones can become lodged in the kidneys, bladder, or any other part of the urinary tract.
  • When the cystine content of the urine surpasses 300 mg/L at a pH of 4.5 to 7.0, cystine crystalluria develops. When the pH of the urine exceeds 7.0, the solubility of cystine increases dramatically.
  • Shapes: Cystine crystals have a distinctive hexagonal shape and should be treated as abnormal if seen in the urine.
  • Colour: The stones may be pink or yellow when removed, but as they are exposed to air, they turn greenish. When no stone forms, cystinuria is usually asymptomatic.
  • Causes: Too much cystine in the urine causes cystinuria. After entering the kidneys, most cystine dissolves and returns to the circulation. Cystinuria is caused by a genetic abnormality that prevents this process from taking place. As a result, cystine accumulates in the urine and crystallises or forms stones.

Triple Phosphate Urine Crystals

Urine Crystals
  • The formation of magnesium ammonium phosphate crystals (triple phosphate crystals) is caused by a combination of factors including decreased urine volume combined with bacteria in the renal system that are capable of producing ammonia and increasing the urine pH.
  • Struvite is a compound made up of three cations (calcium, magnesium, and ammonium) and one anion (phosphate). Despite the fact that pure struvite contains no calcium, they are often known as triple phosphate stones.
  • Shapes: Triple phosphate, or struvite, crystals are described as having a “coffin-lid”-shaped appearance.
  • Colour: Struvite crystallises as white to yellowish or brownish-white pyramidal crystals or platey mica-like forms in the orthorhombic system.
  • Causes: Urinary tract infection with urease-producing bacteria causes urea to be divided into ammonium and urine pH to rise to neutral or alkaline levels, forming struvite stones. Proteus, Pseudomonas, Klebsiella, Staphylococcus, and Mycoplasma are among the bacteria that split urea.

Calcium Oxalate Urine Crystals

  • Kidney stones, which are hard clumps of minerals and other substances that form in the kidneys, are most commonly caused by calcium oxalate crystals. Oxalate, a chemical found in meals like green, leafy vegetables, is mixed with calcium to form these crystals.
  • These crystals may form a solid mass if they adhere together (a kidney stone). One type of chemical that might cause urine crystals is oxalate. This can occur if there is too much oxalate and not enough liquid, and the oxalate “sticks” to calcium when the kidneys are producing urine.
  • Shapes: The crystals of calcium oxalate dihydrate are octahedral. Because they may develop at any pH and naturally occur in normal pee, a considerable fraction of the crystals in a urine sediment will have this form.
  • Color: There are two types of calcium oxalate: calcium oxalate and calcium oxalate. Whewellite is a brown or black mineral that is compact. High urine oxalate concentrations promote its production. However, excessive calcium and magnesium concentrations cause the production of weddellite (colourless) stones.
  • Causes: Calcium oxalate stones are the most frequent form of kidney stone, according to the National Kidney Foundation. These stones can form if there is too much oxalate in the urine. Oxalate is a chemical that can be found in a variety of foods. The kidneys eliminate oxalate from the body through urine as it is digested.

Amorphous Urine Crystals

  • The presence of amorphous crystals is generally of little clinical significance. Their formation is caused by a combination of factors, including decreased urine volume combined with changes in urine pH and often the presence of large quantities of uric acid (meat consumption), or calcium (dairy products) in the diet.
  • The typical oxalate excretion level in the urine is less than 45 (mg/day). A higher level of oxalate in your urine could indicate that you’re at risk for kidney stones. Even at levels above 25 mg/day, which is considered a normal level, the risk of stone formation appears to increase.
  • Shapes and Colour: In acidic urine, amorphous urates (Na, K, Mg, or Ca salts) tend to develop. When discovered in urine, the crystals are frequently hexagonal in shape and may be colourless.
  • Causes: Amorphous phosphate crystals (calcium and magnesium phosphate) are extremely frequent and have minimal therapeutic importance. They’re detected in urine that has a pH higher than 6.5.

Ammonium biurate Urine Crystals

  • When a person’s urine contains too many minerals, pee crystals form. They are frequently found in the kidneys. A urine crystal can turn into a stone if there is an excessive deposition of one or more minerals. Unless large enough stones form, urine crystals usually cause few indications and symptoms.
  • Shape and Color: Brown spheres with sharp thorns make up these gems. They have the appearance of little bugs. They’re most commonly detected in alkaline pee, but they’re also visible in regular urine. Ammonium biurate crystals might emerge in urine samples that are too old or have been poorly stored.
  • Causes: The formation of ammonium urate crystals can be caused by a combination of factors including decreased urine volume or a condition that alkalinizes (increases the pH of) urine, such as a vegetarian diet, urinary tract infection or some medications.

Bilirubin Urine Crystals

  • Bilirubin is made when the healthy destruction of red blood cells occurs. It’s passed through the liver.
  • Shape and Color: Bilirubin crystals have a needle like, granular look and are often quite tiny and yellow in colour. The presence of bilirubin crystals or high amounts of bilirubin in your urine may suggest liver illness or poor liver function.
  • Causes: Bilirubin is a pigment present in bile, a fluid produced by your liver that aids digestion. Your liver will remove the majority of bilirubin from your body if it is healthy. Bilirubin can leak into the blood and urine if your liver is injured. Bilirubin in the urine could indicate liver disease.

Tyrosine Urine Crystals

  • Tyrosine crystals are needle-like and colourless. They’re frequently identified in acidic urine and can be caused by metabolic illnesses such as liver disease or tyrosinemia. Tyrosinemia is characterised by weight loss, fever, diarrhoea, bloody stools, and vomiting.
  • Exercising, eating a nutritious diet, and using drugs to control high blood pressure, high cholesterol, and diabetes are all options for treatment.

Leucine Urine Crystals

  • Leucine crystals are yellow-brown discs with concentric rings. In most cases, leucine crystals aren’t discovered in healthy urine. They’re discovered in pee that’s acidic. They’re typically a sign of serious liver illness. Swelling of the abdomen, vomiting, nausea, dizziness, and malaise are all possible symptoms.
  • Immediate improvement in liver function and health is part of the treatment. Medication to prevent bleeding and minimise swelling caused by excess fluid will be included.

Indinavir Urine Crystals

  • Indinavir is an antiretroviral drug that is used to treat HIV. Crystals can form in the urine as a result of this. Starbursts, rectangular plates, and fans are all examples of indinavir crystals. Back or flank pain are some signs of indinavir crystals.

Further Readings


  1. https://www.medicalnewstoday.com/articles/urine-crystals
  2. https://labpedia.net/urine-crystals-crystalluria/
  3. https://laboratoryinfo.com/types-of-crystals-in-urine/
  4. https://study.com/academy/lesson/crystals-in-the-urine-meaning-and-causes.html
  5. https://medlineplus.gov/lab-tests/crystals-in-urine/
  6. https://www.springer.com/gp/chemistry/biochemistry