Common Urine Crystals and Casts: Introduction, Identification Features, Normal Range and Clinical Singificance

Common Urine Crystals and Casts: Introduction, Identification Features, Normal Range and Clinical Singificance

Common Urine Crystals and Casts

Common Urine crystals and casts in urine routine examination are completed in the following steps- First request the patient to bring a urine specimen. After the arrival of the specimen in the clinical laboratory, take nearly 5 ml of urine and centrifuge it. Put a drop of the mixed sediment part on a clean and grease-free glass slide and place a coverslip over it.  Examine the entire 22- by 22-mm coverslip systematically with the low power objective (10X ) and low light intensity. If any suspicious objects are encountered, examine with the high dry objective (40X). The common urine crystals and casts faced during urine microscopy are calcium oxalate crystals, urate crystals or uric acid crystals, triple phosphate crystals, calcium carbonate crystals, cholesterol crystals, amorphous urates, and amorphous phosphate while casts are hyaline cast, granular cast, fatty casts, waxy casts, white blood cells cast/WBC cast, and crystal casts.

 

Common Urinary Crystals and Cast

Common Urine crystals and casts complete into two phases. A-Common Urinary Crystals, identification features,  and Clinical Significance. B- Common Urinary Casts

Common Urinary Crystals

The common urinary crystals are calcium oxalate crystals,  urate Crystals of uric acid crystals, triple phosphate crystals, calcium carbonate crystals, cholesterol crystals, amorphous urates, and amorphous phosphate.

  • Calcium oxalate crystals: They are colorless crystals and may be found in various shapes like an octahedral, envelope, oval spheres, and biconcave disks that have a dumbbell shape. They are mainly found in acidic and neutral but may also be encountered in alkaline urine. They are associated with both healthy and pathological conditions and can also be seen in urine after ingestion of spinach, tomatoes, garlic, vitamin C, etc.
  • Urate Crystals or Uric acid Crystals: Urate Crystals also called “amorphous urate crystals are found in acidic urine (pH less than 5.5). The formation can be caused by a combination of factors, including a diet rich in meat, decreased urine volume, or a condition that acidifies urine such as chronic diarrhea. They may be found in both healthy and pathological conditions.
  • Triple Phosphate Crystals: They are ammonium magnesium phosphate and colourless prisms with 3 to 6 sides and frequently with the oblique ends. They are found in both healthy and pathological conditions. They are soluble in acetic acid.
  • Calcium Carbonate Crystals: Introduction of Carbonate Crystals or Calcium carbonate Crystals is large circular crystals with radial striations with smooth surfaces in shape. They are slightly brown in color and found in alkaline urine, pH is greater than 6.5. They are caused by a combination of factors including decreased urine volume or a condition that alkalinizes urine, such as a vegetarian diet, chronic diarrhea, urinary tract infections, or certain medications.
  • Ammonium biurate Crystals: These crystals are yellow-brown spherical bodies with or without long, irregular spicules and they are soluble in acetic acid and dissolved by heating.
  • Cholesterol Crystals: Cholesterol Crystals are long rectangles with cut-out corners in shapes and they formed due to renal tubular disease, which can lead to renal failure if left untreated. They are found in both neutral and acid urine and are rarely detected. They’re most likely to appear after the urine sample has been re-frigerated and insoluble in acids and alkalis but soluble in ether, ethanol, and chloroform.
  • Amorphous Urates are salt of sodium, potassium, magnesium, and calcium. The actual form is non-crystalline and amorphous. Their appearance s are yellow-red granular and soluble in alkali at 60°C.
  •  Amorphous phosphates: They are in amorphous, granular form and soluble in acetic acid.

Identification Features of Common Urinary Crystals

 

Calcium oxalate crystals: They are colorless crystals and may be found in various shapes like octahedral, envelope, and dumb-bell shapes.

Urate Crystals or Uric acid Crystals: They show diamond rhombic or rosette form.

Triple Phosphate Crystals: They ate colorless prisms with 3 to 6 sides and frequently with the oblique ends.

Calcium Carbonate Crystals: They are variably sized crystals that frequently appear as large spheroids with radial striations while smaller crystals with a round to ovoid shapes.

Ammonium biurate Crystals: They are yellow-brown spherical bodies with or without long, irregular spicules.

Cholesterol Crystals: They look like clear long rectangles with cut-out corners.

Ammonium biurate Crystals: They appear as brown or yellow-brown spherical bodies with irregular protrusions also called thorn-apples.

Amorphous Urates and Amorphous phosphates are amorphous with granular form.

 

Differences of Amorphous urate and phosphate

Amorphous Urate

  • Found in acidic urine
  • Color of precipitate pink or brick dust
  • Insoluble in acetic acid

Amorphous phosphate

  • Found in alkaline urine
  • White in color
  • Soluble in acidic urine

Common Urinary Crystals Clinical Significances

Calcium oxalate crystals: They are found in diabetes mellitus, liver diseases and
chronic liver diseases.

Urate Crystals or Uric acid Crystals: There is little clinical significance however they can be found in the following conditions like gout or during chemotherapy and kidney stones, acute febrile conditions, and chronic nephritis.

Calcium Carbonate Crystal: It shows little clinical significance even though conditions like decreased urine volume or a condition that alkalinizes urine, such as a vegetarian diet, chronic diarrhea, urinary tract infections, or certain medications. Increased calcium levels that are too high such as immobilization, overactive parathyroid glands, and bone metastases.

Triple phosphate crystals are associated with chronic cystitis, enlarge prostate, and chronic pyelitis.

Ammonium biurate crystals are only clinically significant if they are found in fresh urine.

Cholesterol Crystals: Severe kidney disease or when a lymphatic vessel has ruptured into the renal pelvis.

Amorphous urates and amorphous phosphates have no clinical significance.

Common Urinary Casts Definition, Identification Features, and Clinical Significance

Hyaline casts: The hyaline cast is a type of urinary cast that is simple and most commonly found, which is a cluster of urinary particles, such as cells, fat bodies, or microorganisms, held together by a protein matrix and found in the urine. It can be seen in both healthy and pathological conditions.

Hyaline cast Identification: Appear as clear, tiny tubule-shaped particles

Clinical Significance: Not a dangerous finding, Strenuous exercise, diuretic medications, severe vomiting, or fever.  But large amounts of hyaline casts may indicate kidney damage due to decreased blood flow to the kidneys.

Normal range : 0–2 casts per low power field (LPF) of the microscope

Granular Cast:  The granular cast is cast that contains either proteins, tubular cells, or leukocytes that have broken down.

Principal causes of formation: Exercise or dehydration, acute tubular necrosis.
Granular cast in Urinary Sediment Microscopy

Fatty Cast-Formation of the fatty cast: It is formed by the breakdown of lipid-rich epithelial cells, these are hyaline casts free globules of fat or oval fat bodies inclusions, yellowish-tan in color.

Clinical Significance: Fatty cast in urinary sediment is faced in various clinical conditions like the high urinary protein nephrotic syndrome, diabetic or lupus nephropathy or toxic renal poisoning, or larger-scale necrosis or epithelial cell death.

Stain: Fatty cast has globules of fat, either as triglyceride or neutral fat, that stains with fat stain, or as cholesterol, which will unify as a Maltese cross.

Identification features Presence of refractile lipid droplets within the protein matrix of the cast.

Waxy Cast- Definition of Waxy Cast: It is a form of urinary cast consisting of homogeneous proteinaceous material that has a high refractive index, in contrast to the low refractive index of hyaline casts; waxy casts probably represent an advanced stage of the disintegrative process that results in coarsely and finely granular casts and are usually indicative of advanced renal disease. Source-Farlex Partner Medical Dictionary © Farlex 2012

Clinical Significance: Amyloidosis, postinfectious glomerulonephritis, and frequent association in Increased levels of serum creatinine

Identification Feature: Broken off or blunt ends, notched and sharp margins, lateral cracks, high refractive index, and a surface whose appearance is reminiscent of that of melted wax.

White blood cells (WBC) Cast:

WBC cast: White blood cell casts or WBC casts in routine urinalysis refer to a hyaline matrix cast bearing neutrophil inclusions.

Identification Features: WBCs in a cast

Stain: WBC cast stained with Naphtyl AS-D chloro-acetate esterase

Clinical Significance Tubular disease, especially infection and acute pyelonephritis

Crystal Casts:  Crystal Casts are crystallized urinary solutes, such as oxalates, urates, or sulphonamides, etc, that may become enmeshed within a ketanaline cast during its formation. Clinical Significance They show little clinical significance.

 

Keynotes on Common Urine Crystals and Casts

  •  Red Blood Cell (RBC) casts are strongly indicative of granulomatosis with polyangiitis, systemic lupus erythematosus (SLE), post-streptococcal glomerulonephritis, or Goodpasture’s syndrome.
  • The crystals that can be found in the urine of healthy individuals are calcium oxalates, amorphous urates, uric acid/ urate, amorphous phosphates, etc.
  • Some crystals may indicate an abnormal metabolic process and they are cystine, calcium carbonate, tyrosine, leucine, etc.

 

Common Urine Crystals and Casts Videos Links

The common urine crystals and casts links videos of Urinary Sediment Microscopy are provided as follows-

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