final cast and crystals

Hyaline cast nonpathologic

stress, exercise, heat exposure, dehydration

Hyaline cast pathologic

acute glomerulonephritis, pyelonephritis, chronic renal disease, congestive heart failure

Casts

Elements unique to the kidney that are formed in the DCT and collecting duct, with parallel sides and rounded ends. They are detected under low power and identified under high power by scanning the edges of a glass cover slip. Low light is essential for their detection. The number of casts per low power field should be reported.

Uromodulin

A major constituent of cast composition, consistently excreted in normal conditions, but increased during stress and exercise. The formation of protein fibrils into a matrix is influenced by urine stasis, acidity, sodium, and calcium levels. Uromodulin protein cannot be detected by reagent strips, and increased protein in casts is indicative of renal disease rather than uromodulin.

Cylindroids

Casts with tapered ends, which have the same significance as regular casts. The presence of cylindroids indicates the presence of urinary casts.

Hyaline Casts

Casts with a low refractive index, appearing colorless when unstained. They are composed of uromodulin protein and can be detected using low light or phase microscopy. Hyaline casts have normal parallel sides and rounded ends, and may appear wrinkled or cylindroid, with occasional adhering cells or granules.

RBC Casts

Casts with an orange-red color, embedded and adhering cells, and may be fragmented. To confirm the presence of RBC casts, freestanding RBCs should be seen and the reagent strip for blood should test positive. It is important to look for the cast matrix to avoid mistaking a clump of RBCs for a cast.

WBC Casts

Casts seen with infection and inflammation of the nephron. In pyelonephritis, WBC casts are accompanied by bacteria, while in acute interstitial nephritis, WBC casts are present without bacteria. WBC casts may also accompany RBC casts in glomerulonephritis. Mostly neutrophils with lobed nucleus and granules are seen in WBC casts, and staining can help differentiate them from renal tubular epithelial (RTE) cells.

Bacterial Casts

Casts seen in pyelonephritis, which may be pure bacteria or mixed with WBCs. They resemble granular casts and should be confirmed by the presence of free WBCs and bacteria, as well as a Gram stain.

Renal Tubular Epithelial Cell Casts

Casts associated with tubular damage, heavy metals, viral infections, drug toxicity, graft rejection, and pyelonephritis. These casts may appear bilirubin stained, and the presence of a matrix helps distinguish them from fragments.

formed in DCT=smaller, round cells, oval cells

fibrils forming cast pull cells from damaged tubules

Differentiate from WBCs: stain to show single nucleus

Fatty Casts

Casts seen in nephrotic syndrome, diabetes, crush injuries, and tubular necrosis. They are associated with oval fat bodies (OFBs) and fat droplets, and appear highly refractile. oval fat bodies may attach to matrix. Polarized microscopy and lipid stain can be used to confirm their presence. triglycerides and neutral fats stain orange

Granular Casts

Casts that are coarse and finely granular. They originate from RTE lysosomes and are excreted in normal metabolism, with increased production after exercise and activity. Disease states can lead to the disintegration of cellular casts and tubule cells or the filtration of protein aggregates by the glomerulus. Granular casts can be differentiated from debris and crystals by looking for the presence of a matrix.

granules disintegrate to form waxy casts

Waxy Casts

Casts that are brittle, highly refractile, and often fragmented with jagged ends and notches. They stain a homogenous dark pink and are associated with degenerated hyaline and granular casts. Waxy casts are seen in cases of extreme urine stasis and renal failure.

Broad Casts

Casts associated with renal failure, characterized by the destruction and widening of the DCTs. They are formed in the upper collecting duct and can be of various types, with granular and waxy casts being the most common. Broad casts may appear bile stained in cases of viral hepatitis.

Urinary Crystals

Geometrically formed structures or amorphous material found in urine. Most crystals are not clinically significant but should be reported. Differentiation from abnormal crystals indicating liver disease, inborn errors of metabolism, and tubular damage is important. Iatrogenic crystals can be caused by medications.

Crystal Formation

Crystals are formed by the precipitation of urine solutes such as salts, organic compounds, and medications. Formation is influenced by temperature, solute concentration, and pH. Refrigerated specimens may contain more crystals, while fresh specimens require a high specific gravity. Organic and iatrogenic compounds crystallize more easily in acidic pH.

General Identification Techniques

Most crystals have characteristic shapes and colors. Urine pH is a valuable identifier, with abnormal crystals found in acid urine. Polarized microscopy characteristics are also helpful in identifying crystals.

Crystal Formation

The process of forming crystals in urine, influenced by temperature and pH.

Amorphous urates

Granules that form in refrigerated acid urine and dissolve when warmed.

Amorphous phosphates

Granules that form in refrigerated alkaline urine and dissolve in acetic acid.

RBCs

Red blood cells that lyse (break down) with acetic acid.

Normal Crystals Seen in Acidic Urine

Crystals commonly observed in acidic urine, including amorphous urates, uric acid, acid urates, sodium urates, and calcium oxalate.

Amorphous urates

Yellow-brown granules microscopically

Urine sediment has pink color due to the pigment uroerythrin attaching on surface of granules

pH usually greater than 5.5

Uric acid crystals

Crystals with rhombic, whetstone, wedge, or rosette shapes, yellow-brown in color, and associated with conditions like leukemia, Lesch-Nyhan syndrome, and gout.

may resemble cystine crystals but always polarize

increased purines and nucleic acids

Calcium oxalate crystals

monohydrate is oval or dumbbell shapes, dihydrate is envelope or two pyramid-shaped, seen in acid and neutral pH, and associated with conditions like antifreeze poisoning and renal calculi.

Sodium urates

Needle-shaped crystals seen in synovial fluid during gout episodes and may appear in urine.

Normal Crystals Seen in Alkaline Urine

Crystals commonly observed in alkaline urine, including amorphous phosphates, triple phosphate, calcium phosphate, calcium carbonate, and ammonium biurate.

Amorphous phosphates

Granular in appearance

May appear similar to amorphous urates

Alkaline pH and heavy white precipitate after refrigeration

Triple phosphate crystals

Colorless, prism, or coffin-lid shaped crystals found in highly alkaline urine and urinary tract infections (UTIs).

birefringent under polarized light, no clinical significance

urea-splitting bacteria

Calcium phosphate crystals

Colorless, flat rectangles, and thin prisms in rosettes, with no clinical significance.

Calcium carbonate crystals

Small, colorless, dumbbell, and spherical shapes, producing gas with the addition of acetic acid, birefringent, and no clinical significance.

Ammonium biurate crystals

Yellow-brown, spicule-covered spheres known as "thorny apples," found only in alkaline urine and old specimens with urea-splitting bacteria.

Abnormal Urine Crystals

Crystals found in acidic urine that have characteristic shapes and are confirmed by patient disorders and medications.

Cystine crystals

Colorless, hexagonal, thin and thick plates, seen in cystinuria, a metabolic disorder that affects cystine reabsorption by renal tubules (from renal calculi at early age).

can be difficult to differentiate from colorless uric acid crystals

confirm test is cyanide nitroprusside (red to purple color test result)

Cholesterol crystals

Refrigerated specimens only. Rectangular plates with notched corners, highly birefringent, and associated with nephrotic syndrome (accompanying fatty casts and oval fat bodies and heavy proteinuria)

Radiographic dye crystals

Crystals similar to cholesterol crystals, polarize, and require patient history and comparison with other urine analyses for identification. very high SG with refractometer

Crystals Associated With Liver Disease

Crystals associated with hepatic disorders, including tyrosine crystals, leucine crystals, and bilirubin crystals.

Tyrosine crystals

Fine colorless to yellow needles in clumps or rosettes, seen with leucine crystals, and associated with inherited amino acid disorders. usually a positive bilirubin on dipstick

Leucine crystals

Yellow-brown spheres with concentric circles and radial striations, accompanied by tyrosine crystals, seen less frequently than tyrosine crystals.

Bilirubin crystals

Clumped needles or granules with a characteristic bright yellow color, associated with hepatic disorders like viral hepatitis with tubular damage.

Sulfonamide crystals

Crystals formed due to dehydration and possible tubular damage, appearing as needles, rhombics, whetstones, sheaves of wheat, and rosettes. colors ranging from colorless to yellow-brown

Ampicillin crystals

Colorless needles that form bundles after refrigeration, associated with extreme dehydration.

Urinary Sediment Artifacts

Non-crystalline substances found in urine sediment, including starch granules, oil droplets, air bubbles, pollen grains, vegetable fibers, and fecal decontamination diaper fiber.

Starch granules

Granules with a dimpled center and highly refractile appearance.

Fecal material

Particles of feces found in urine sediment.

Pollen grain

Grains from plants that may appear in urine sediment, characterized by concentric circles.

Urinary Sediment

The solid particles that are present in urine and can be examined under a microscope.

Artifacts

Substances or particles that may be present in urinary sediment but are not of clinical significance.

Fiber

A thin, thread-like structure that can be found in urinary sediment and may be mistaken for casts.

Squamous Epithelial Cell

A type of cell that is flat and scale-like in appearance, commonly found in the urinary sediment.

Polarized

Refers to the use of polarized light to examine urinary sediment, which can help differentiate between fibers and casts.

Refractile

Having the ability to bend or change the direction of light, causing it to appear bright or shiny.

Casts

Cylindrical structures that can be found in urinary sediment, formed by the accumulation of materials in the renal tubules.

Hair

Strands of protein that may be present in urinary sediment and can be mistaken for casts.

Clothing

Fabric fibers that may be present in urinary sediment and can be mistaken for casts.

Diapers

Fibers from diapers that may be present in urinary sediment and can be mistaken for casts.

Vegetable Fiber

Plant-based fibers that may be present in urinary sediment and can resemble waxy casts.

Hyaline Cast

A type of cast that is transparent and colorless, often found in urinary sediment.

Waxy Cast

A type of cast that has a waxy appearance and can resemble vegetable fibers in urinary sediment.

Non-parallel sides

Refers to the shape of vegetable fibers in urinary sediment, where the sides are not parallel to each other.