Part 5

Urinalysis and body fluids

Bring specimen handling, urine chemistry, microscopy, and body-fluid findings into one interpretation.

Steps

Urine specimens and storage15 min · Decide whether a urine specimen meets the requested test's requirements · Predict changes caused by delayed urine examination · Select a urine collection type suited to the requested measurement
Timed and forensic collections15 min · Recognize an incomplete or mistimed urine collection before calculation · Maintain chain of custody for a federal workplace urine specimen
The nephron, appearance and concentration16 min · Match a nephron segment to its role in filtration, reabsorption, or secretion · Confirm a urine color or clarity finding with the reagent strip and microscopy · Explain a discrepancy between refractometric and strip specific gravity
The reagent strip: protein and glucose18 min · Perform urine reagent strip testing with the specified read times and quality checks · Recognize the protein pad's albumin selectivity and its limits for nonalbumin protein · Choose a quantitative albumin-to-creatinine ratio to follow up a urine albumin screen · Tell which sugars the glucose oxidase pad detects and which need copper reduction
The reagent strip: blood, bile pigments and infection16 min · Compare a positive urine blood pad with the red cells seen on microscopy · Check light, delay, and interferents before reporting urine bilirubin or urobilinogen · Recognize infections that a negative nitrite or leukocyte esterase pad can miss
Cells in the sediment16 min · Recognize urinary acanthocytes and their glomerular association · Select an optical method for faint structures in unstained urine · Read many squamous cells as a sign of a poorly collected urine specimen · Recognize renal tubular cells and report them as a sign of tubular injury
Oval fat bodies, yeast and artifacts15 min · Recognize an oval fat body and confirm its lipid by polarization or fat stain · Distinguish yeast from red cells using budding and related features · Distinguish contaminants and pseudocasts from true urine sediment
Urine crystals14 min · Identify common urine crystals by shape, urine pH, color, and birefringence · Recognize colorless hexagonal crystals that need a cystine confirmation test
How casts form15 min · Explain where and how urinary casts form · Distinguish a true cast matrix from a free aggregate of cells · Tell a few physiologic hyaline casts from the increased numbers seen in renal disease
Cellular casts and renal patterns17 min · Interpret an RBC cast as evidence of bleeding within the nephron · Distinguish the renal evidence of a WBC cast from free urinary leukocytes · Place renal injury in glomerulus or tubule from protein, heme, cells, and casts together
Body fluid counts and CSF appearance15 min · Choose manual confirmation when a body-fluid count falls outside the verified range · Recognize cytocentrifuge distortion that mimics abnormal cells on a body-fluid slide · Name the abnormal findings that a clear, colorless CSF can still contain
CSF glucose, IgG and infection limits18 min · Recognize why normal CSF findings cannot exclude a device-associated infection · Compare CSF glucose with a blood glucose drawn close to the lumbar puncture · Calculate the IgG index from paired CSF and serum IgG and albumin results · Distinguish CSF-restricted IgG bands from a matched systemic pattern
Synovial fluid crystals and infection16 min · Distinguish urate and CPP crystals by shape and compensated polarization · Recognize septic arthritis risk despite crystals or an overlapping cell count
Pleural and peritoneal fluids16 min · Name the pressure, permeability, or lymphatic change that produces an effusion · Classify a pleural effusion as transudate or exudate with Light's criteria · Calculate and interpret the serum-ascites albumin gradient
Amniotic fluid and semen16 min · Name the interferences that make a rupture-of-membranes test misleading · Decide whether a semen collection is complete and timely enough to analyze · Calculate total sperm number from concentration and ejaculate volume · Distinguish sperm immotility from loss of vitality
Stool testing17 min · Calculate a stool osmotic gap from stool electrolyte results · Tell fecal immunochemical testing (FIT) from guaiac testing by what each detects · Check the fat-controlled diet and timed collection before interpreting fecal fat · Recognize when watery stool falsely lowers a fecal elastase result

What you'll be able to do

From nephron to urine

Acceptability

Color

Confirm a urine color or clarity finding with the reagent strip and microscopy

Measurement principles

Explain a discrepancy between refractometric and strip specific gravity

Strip workflow and quality control

Optical methods

Casts

Clinically significant and drug-associated crystals

Selecting and controlling a cell-count method

Appearance and blood contamination

Crystal examination

Collection and timing

Stool electrolytes and the osmotic gap

Cerebrospinal fluid

Recall the ASCP MLS examination range for CSF glucose
Recall the ASCP MLS examination range for urine pH

On paper

06 / 10 · Urinalysis and Other Body Fluids

Urine casts: brightfield

Seven cast patterns, identifying features, and common look-alikes

Casts form in renal tubules in a uromodulin protein matrix. Identify the matrix first, because loose cell clumps can mimic casts.

Brightfield: transparent casts have little contrast. Reduced illumination helps reveal their outline, and phase contrast can clarify cell detail.

Photo	Cast and identifying feature	Association and look-alike
	Hyaline · 400× Pale matrix with parallel sides. Faint edges can disappear in strong illumination.	Concentrated urine, exercise, or renal disease. A few may occur without disease. Look-alike: Mucus tapers and varies in width.
	Red cell · 400× Red cells within a continuous matrix.	Bleeding within the nephron, especially from a glomerular source. Look-alike: Free red cell clumps have no enclosing cast matrix.
	White cell · 400× Granular white cells in a matrix. Nuclear lobes may be difficult to resolve.	Renal inflammation, including pyelonephritis and interstitial nephritis. Look-alike: Tubular cells or white cell clumps can resemble a cast.
	Epithelial / white cell · 400× The source labels this as an epithelial/white-cell cast. Indistinct nuclei limit cell typing.	Tubular injury or renal inflammation. The cast alone cannot establish the cause. Look-alike: White cell and tubular cell casts can look alike. Compare the nuclei, because size alone cannot separate them.
	Granular · 400× Coarse or fine granules fill the matrix as cells and proteins break down.	Numerous muddy brown casts support tubular injury. A few granular casts are less specific. Look-alike: Debris or crystal clumps lack a continuous cast outline.
	Fatty · 400× Refractile lipid droplets within a matrix. Some droplets show Maltese crosses in polarized light.	Lipiduria, often with heavy proteinuria. Look-alike: Starch granules also form crosses. Confirm that the droplets lie within a cast.
	Waxy · 400× Highly refractile, sharply outlined matrix with cracks, notches, and blunt ends.	Prolonged tubular stasis, often with advanced renal impairment. Look-alike: Fibers have irregular edges and lack a cast matrix.

Scan at low power, then identify contents at higher power. Examine fresh urine, because delay and dilute alkaline urine can destroy casts.

Photos: Bert Grijsen, Microscopic Urine Examination (2026). CC BY-SA 4.0. Cropped; mixed cast rotated; colors unchanged. Magnifications are the source's stated values and do not describe the printed size.

Urinalysis and Other Body Fluids06 / 10Urine casts: brightfieldSeven cast patterns, identifying features, and common look-alikes

05 / 10 · Urinalysis and Other Body Fluids

Urine casts: phase contrast

Seven cast types, identifying features, and common look-alikes