Urinalysis – Key Points & Review Questions

These question-and-answer flashcards review the essential concepts, definitions, laboratory values, and clinical correlations from the Urinalysis lecture. They can be used for self-testing and rapid revision before exams.

What is oliguria and what causes it?

A significantly reduced urine output, often seen with dehydration and severe burns

Which two disorders are classic causes of polyuria?

Diabetes mellitus and diabetes insipidus.

How does urine appear in diabetes mellitus versus diabetes insipidus?

DM: dilute-looking urine with HIGH osmolality; DI: dilute urine with LOW osmolality.

Which pigment causes dark-amber (beer-brown) urine?

Conjugated bilirubin.

Cloudy pink or red urine usually indicates the presence of what?

Intact red blood cells (hematuria).

Clear pink or red urine suggests what possible substances?

Free hemoglobin, myoglobin, or porphyrins.

Which medication commonly turns urine dark orange?

Phenazopyridine (Pyridium) or rifampin.

How are dipstick protein results reported and what is a normal result?

Negative, Trace, 1+ to 4+; normal is Negative or Trace (≤ 150 mg/day).

Which urinary protein is most readily detected by the dipstick?

Albumin.

What confirmatory test is used for positive dipstick protein results?

Sulfosalicylic acid (SSA) precipitation test.

At what protein excretion level (24-hr collection) is proteinuria considered pathologic?

Greater than 150 mg/day

Give two transient benign causes of proteinuria.

Strenuous exercise and pregnancy (without pre-eclampsia).

Which plasma-cell malignancy causes prerenal proteinuria with Bence-Jones proteins?

Multiple myeloma.

What post-renal conditions can produce proteinuria?

Pyelonephritis, cystitis, urethritis, or prostatitis.

What lab threshold is proof of glucose in the urine?

160–180 mg/dL.

Which confirmatory tablet test detects reducing sugars in urine?

Clinitest.

Name the three ketone bodies.

Acetoacetic acid, acetone, and β-hydroxybutyric acid.

What clinical situations commonly give a positive ketone test?

Diabetic ketoacidosis, starvation, high-fat/low-carb diets, severe vomiting, or alcoholism.

What dipstick pad detects blood in urine and how are results verified?

The blood/hemoglobin pad; verify by microscopy for RBCs.

Give two causes of hemoglobinuria without intact RBCs.

Hemolytic transfusion reaction and extensive burns.

List two conditions that may lead to myoglobinuria.

Rhabdomyolysis and myocardial infarction.

Why is unconjugated bilirubin absent from urine?

It is not water-soluble.

Which confirmatory test is used for urinary bilirubin?

Ictotest tablet test.

Positive urine bilirubin suggests which three broad categories of disease?

Hemolysis, hepatocellular disease, or biliary obstruction.

What is the normal reference range for urobilinogen in urine?

0.2 – 1.0 mg/dL (reported as ‘normal’).

Increased urinary urobilinogen can indicate what two main situations?

Pre-hepatic hemolysis or hepatocellular disease.

Decreased or absent urobilinogen suggests what problem?

Intra- or extra-hepatic biliary obstruction.

What organisms convert nitrate to nitrite in urine?

Common Gram-negative urinary pathogens such as Escherichia coli or Proteus species.

Why can a nitrite-negative urinalysis NOT rule out UTI?

Some bacteria do not reduce nitrate, or urine may not have remained in bladder long enough.

What does a positive leukocyte esterase (LE) indicate?

Pyuria—an increased number of WBCs in urine.

Which infections may give positive LE but negative nitrite results?

Trichomonas, yeast, Chlamydia, Gonorrhea, or Mycoplasma infections.

Define urine specific gravity.

The ratio of urine density to water (water = 1.000).

What is the normal specific gravity range for an average urine sample?

1.005 – 1.030.

List three causes of high specific gravity.

Glucosuria, proteinuria, dehydration, mannitol therapy, or radiographic contrast media.

Very low specific gravity with polyuria suggests which endocrine disorder?

Diabetes insipidus.

Which measurement is more accurate than specific gravity for solute concentration?

Osmolality (mOsm/kg).

When is urine osmolality most useful diagnostically?

In evaluating polyuria when diabetes mellitus is excluded (e.g., diabetes insipidus).

Name five classes of insoluble materials assessed in urine microscopy.

Cells (RBC/WBC), epithelial cells, casts, crystals, and microorganisms/‘junk’.

What is the normal microscopic range for RBCs in urine?

0–2 cells per high-power field (hpf).

List two non-renal causes of hematuria.

Urinary tract stones or tumors, trauma, or prostatitis.

What urinary findings accompany hematuria from glomerular disease?

Proteinuria and RBC casts.

Define pyuria.

Presence of increased white blood cells in urine.

Which urinary findings differentiate cystitis from pyelonephritis?

Pyelonephritis shows WBC casts and higher proteinuria; cystitis does not.

Large numbers of squamous epithelial cells in urine suggest what?

A contaminated (poorly collected) sample.

Renal tubular epithelial cells in urine indicate what pathology?

Tubular necrosis or damage.

Where in the nephron are casts formed?

Distal convoluted tubule and collecting duct.

Name four factors that enhance cast formation.

Acidic pH, high concentration (high SG), proteinuria, and urinary stasis.

What protein forms the primary matrix of urinary casts?

Tamm-Horsfall protein.

What is the normal range for hyaline casts?

0–2 per low-power field (lpf).

Strenuous exercise may transiently increase which type of cast?

Hyaline casts.

Which casts are pathognomonic for glomerular bleeding?

Red blood cell casts.

White blood cell casts typically indicate what condition?

Kidney infection or nephron inflammation (e.g., pyelonephritis).

RTE cell casts suggest which category of renal disease?

Intrinsic renal tubular disease.

What does the presence of waxy casts signify?

Severe chronic renal stasis, often seen in end-stage renal failure.

Fatty casts are especially associated with which nephrologic syndrome?

Nephrotic syndrome.

Broad casts are sometimes called what, and why?

‘Renal failure casts’ because they form in dilated tubules during severe stasis.

Why is urine pH helpful when identifying crystals?

Many crystals form only in either acidic or alkaline urine.

Which acid-pH crystal appears as yellow-brown rosettes or rhomboids and is linked to gout?

Uric acid crystals.

Describe the appearance of calcium oxalate crystals.

Colorless octahedrons resembling envelopes; dumbbell or oval forms possible.

What urine finding is characteristic of cystinuria?

Colorless hexagonal cystine crystals.

Which crystal type with notched rectangular plates is often seen in nephrotic syndrome?

Cholesterol crystals.

Leucine and tyrosine crystals point toward what underlying organ disease?

Severe liver disease

Name the distinctive ‘coffin-lid’ crystal found in alkaline urine.

Triple phosphate crystals.

What microorganism may mimic RBCs but shows budding on microscopy?

Yeast (Candida species).

Which motile flagellate parasite is commonly detected in urine?

Trichomonas vaginalis.