# URINALYSIS INTERPRETATION: PRACTICAL GUIDE

## PA/Medical Student Handout

------------------------------------------------------------------------

## LEARNING OBJECTIVES

By the end of this module, you will be able to:

1.  **Understand dipstick chemistry** and limitations
2.  **Interpret proteinuria** (dipstick vs. quantitative measures)
3.  **Differentiate hematuria** from other causes of color
4.  **Recognize false positives/negatives** in proteinuria and hematuria
5.  **Interpret microscopy findings** (casts, crystals, cells)
6.  **Apply urinalysis to clinical scenarios** (UTI, GN, CKD, nephrotic syndrome)
7.  **Know when to send urine cultures** and specialized tests

------------------------------------------------------------------------

## SECTION 1: DIPSTICK BASICS

### How Dipstick Works

**Reagent Pads on Standard Dipstick**:

| Component | Chemical Reaction | What It Detects |
|----|----|----|
| **Protein** | pH indicator (bromophenol blue) | Albumin primarily; insensitive to Bence Jones proteins |
| **Glucose** | Glucose oxidase | Free glucose (filtered at normal GFR) |
| **Ketones** | Nitroprusside reaction | Ketones (DKA, starvation) |
| **Blood/RBC** | Peroxidase-like activity | Heme, hemoglobin, myoglobin |
| **Nitrites** | Griess reaction | Gram-negative bacteria (E. coli) |
| **Leukocyte esterase** | Indoxyl carbinol | WBC (neutrophil granules); also some bacteria |
| **pH** | Methyl red/methylene blue | Urine pH |
| **Specific gravity** | Change in pKa | Urine concentration |
| **Bilirubin** | Diazo reagent | Conjugated bilirubin |
| **Urobilinogen** | Ehrlich reaction | Urobilinogen |

### Timing and Storage

- **Read at correct time**: Usually 60 seconds (varies by manufacturer)
- **Exposure to light**: Degrades reagents
- **Temperature**: Cold urine may give false negatives
- **Air exposure**: Nitrites and leukocyte esterase degrade
- **Refrigeration**: Prolongs accuracy; room temperature deteriorates within 2 hours

------------------------------------------------------------------------

## SECTION 2: PROTEIN IN URINE

### Dipstick Proteinuria Interpretation

**Dipstick Grading**: - **Negative**: \<10 mg/dL - **Trace**: 10-15 mg/dL - **1+**: 30 mg/dL - **2+**: 100 mg/dL - **3+**: 300 mg/dL - **4+**: ≥1000 mg/dL (nephrotic-range)

### Critical Limitations of Dipstick

**False Positives** (positive dipstick with low actual protein): 1. **Concentrated urine** (high specific gravity, dehydration) 2. **Alkaline urine** (pH \>7; dipstick more sensitive in alkaline conditions) 3. **Gross hematuria** (hemoglobin itself positive with dipstick) 4. **Contaminating blood** (even from traumatic catheterization) 5. **Quaternary ammonium compounds** (residual antiseptic on collection containers) 6. **Contrast agents** (from recent imaging)

**False Negatives** (negative dipstick with actual proteinuria): 1. **Bence Jones proteins** (immunoglobulin light chains; multiple myeloma) - Dipstick primarily detects albumin - Light chain proteins may not react - Require specialized tests (serum/urine protein electrophoresis, free light chains)

1.  **Myoglobin** (rhabdomyolysis)
    - Small molecular weight
    - May be missed or underestimated by dipstick
2.  **Dilute urine** (excessive hydration)
    - Protein concentration too low to trigger dipstick

### Quantifying Proteinuria

**When to use QUANTITATIVE measures**: - Dipstick ≥1+ (significant) - Ongoing monitoring needed - Nephrotic syndrome workup - CKD monitoring

**Available Tests**:

| Test | Specimen | Advantages | Disadvantages |
|----|----|----|----|
| **Spot Urine ACR** | Random (most common) | Easy, convenient, best for ongoing monitoring | Affected by timing, posture |
| **Spot Urine PCR** | Random | Includes all proteins | Albumin-specific assay needed for ACR |
| **24-Hour Urine** | Timed collection | Gold standard; captures variation | Burdensome; collection errors common |
| **Urine Protein Electrophoresis** | Random or 24h | Identifies protein type | Specialized; expensive |
| **Serum/Urine Free Light Chains** | Serum + random urine | Detects light chain disease | Expensive; not routine |

**Interpreting Spot ACR/PCR**:

| Protein Level | ACR (mg/g) | PCR (mg/g) | Clinical Significance |
|----|----|----|----|
| **Microalbuminuria** | 30-300 | 50-500 | Diabetes, early CKD; requires intervention |
| **Nephrotic range** | \>300 | \>500 | Nephrotic syndrome; requires kidney biopsy |

------------------------------------------------------------------------

## SECTION 3: HEMATURIA

### Dipstick Blood/RBC Interpretation

**Dipstick Blood Positive Indicates**: - RBCs - Hemoglobin (from lysed RBCs) - Myoglobin (muscle breakdown) - ⚠️ **Cannot distinguish between them**

### Microscopy Differentiation

**With RBCs on microscopy** (dysmorphic): - True hematuria (from kidney or urinary tract) - If RBC casts present → **glomerulonephritis** (RPGN, IgAN, etc.)

**Without RBCs on microscopy** (dipstick positive): - Hemoglobinuria (intravascular hemolysis) - Myoglobinuria (rhabdomyolysis) - **False positive** (from other causes below)

### False Positives for Hematuria

**Cause 1: Contaminating Blood** - Traumatic catheterization - Menses in women - Hematospermia in men - Management: Repeat clean-catch specimen; wait 48 hours if traumatic catheterization

**Cause 2: Pigmenturia (Hemoglobin-Like)** - **Hemoglobinuria** (intravascular hemolysis) - Severe hemolysis → hemoglobin exceeds renal reabsorption capacity - Dipstick positive; no RBCs on microscopy - Management: Check free plasma hemoglobin, LDH, bilirubin, reticulocyte count

- **Myoglobinuria** (rhabdomyolysis)
  - Muscle breakdown releases myoglobin
  - Dipstick positive; no RBCs on microscopy
  - Associated with CK elevation, brown urine color
  - Management: Check CK, urine myoglobin, creatinine (AKI risk)

**Cause 3: Oxidizing Agents** - Hydrogen peroxide contamination - Bleach exposure - Rare but documented

### Clinical Approach to Hematuria

**Step 1: Microscopy** - RBCs present? (True hematuria) - RBC casts? (Glomerulonephritis) - No RBCs? (Hemoglobinuria or myoglobinuria)

**Step 2: Additional Tests if Needed** - Free plasma hemoglobin (hemolysis) - Creatine kinase (rhabdomyolysis) - LDH, bilirubin, reticulocyte count (hemolysis workup) - Urine myoglobin (rhabdomyolysis)

**Step 3: Clinical Context** - Dysmorphic RBCs + RBC casts = **Glomerulonephritis** (biopsy candidate) - Isomorphic RBCs without casts = **Lower urinary tract source** (cystitis, stone, malignancy) - No RBCs + positive dipstick = **Hemoglobinuria or myoglobinuria** (investigate cause)

------------------------------------------------------------------------

## SECTION 4: MICROSCOPY FINDINGS

### Cells in Urine

| Finding | Normal | Abnormal Significance |
|----|----|----|
| **RBCs** | 0-3/lpf | \>5 = hematuria; dysmorphic = GN |
| **WBCs** | 0-5/lpf | \>5 = pyuria (UTI, pyelonephritis, interstitial nephritis) |
| **Bacteria** | None | Present in UTI; should correlate with LE+ and nitrites |
| **Epithelial cells** | Few | Numerous = contaminated specimen (improper collection) |
| **Squamous cells** | Few | Numerous = contaminated (urethral epithelium) |

### Casts

**What are Casts?** - Cylindrical protein precipitates formed in collecting duct - Composed of Tamm-Horsfall protein (uromodulin) + cellular inclusions - Always abnormal (except rare hyaline in concentrated urine)

| Cast Type | Meaning | Associated Condition |
|----|----|----|
| **RBC casts** | RBCs in cast matrix | **ALWAYS means glomerulonephritis** (urgent biopsy) |
| **WBC casts** | WBCs in cast matrix | Pyelonephritis, interstitial nephritis, SLE |
| **Granular casts** | Granular debris | Non-specific; CKD, acute illness |
| **Muddy brown casts** | Cellular debris, myoglobin | Acute tubular necrosis (AKI) |
| **Waxy casts** | Degenerated cellular cast | Chronic kidney disease (ominous) |
| **Hyaline casts** | Tamm-Horsfall protein only | May be normal in concentrated urine; otherwise abnormal |
| **Fatty casts** | Fat droplets in matrix | Nephrotic syndrome |
| **Broad/renal failure casts** | Large diameter casts | Severe CKD, renal failure |

### Crystals

| Crystal | pH | Clinical Significance |
|----|----|----|
| **Calcium oxalate** | Acidic | Normal finding; \>100/lpf suggests stone disease |
| **Uric acid** | Acidic | Normal; excessive in gout, tumor lysis syndrome |
| **Calcium phosphate** | Alkaline | Normal |
| **Triple phosphate** (struvite) | Alkaline | Urease-producing bacteria (Proteus); stone disease |
| **Bence Jones** (immunoglobulin light chains) | Variable | **Multiple myeloma** (requires serum/urine protein electrophoresis for confirmation) |
| **Cystine** | Acidic | Cystinosis (genetic disorder) |

### Microorganisms

**Bacteria**: - **None**: Normal - **Few**: Likely contamination - **Numerous (\>5/lpf)**: Suggests UTI; quantify with culture

**Yeast** (Candida): - Vaginal contamination (women) - True candiduria (catheters, immunocompromised) - Usually not clinically significant unless symptoms present

------------------------------------------------------------------------

## SECTION 5: SPECIAL SITUATIONS

### Orthostatic Proteinuria

**Definition**: Protein present in daytime urine but absent in overnight urine

**Characteristics**: - More common in young, tall, thin males (5-15%) - Completely **benign**; excellent long-term prognosis - Due to postural changes and increased capillary pressure upright

**Diagnosis**: - Split collection: daytime vs. overnight urine - Daytime shows protein; overnight shows none - Can follow up with repeat spot urine in morning

**Clinical Pearl**: If orthostatic proteinuria diagnosed, reassure patient and no further workup needed

### Transient Proteinuria

**Causes**: - Fever - Stress - Seizures - Extreme exercise (marathon running → can reach nephrotic levels) - Vigorous physical activity

**Management**: - Repeat testing when patient returns to baseline - Usually resolves within 24-48 hours

### Contamination Issues

**Signs of Contamination**: - **Numerous squamous epithelial cells** (\>5/lpf) = improperly collected specimen - **Numerous bacteria without pyuria** = likely contamination - **RBCs + bacteria in female** = consider menses as source

**Proper Collection**: - Women: Cleanse urethral meatus; midstream catch - Men: Retract foreskin; midstream catch - Avoid external contamination

------------------------------------------------------------------------

## SECTION 6: URINE CULTURE

### When to Culture

**Send Culture When**: - Pyuria (WBC \>5/lpf) + symptoms of UTI - Hematuria + pyuria (rule out infection) - Fever + lower abdominal pain - Pyelonephritis symptoms (fever, flank pain, CVA tenderness) - Catheterized patients with symptoms - Asymptomatic bacteriuria (only in pregnancy, pre-urologic procedures)

**Do NOT Culture**: - Asymptomatic bacteriuria (except pregnancy) - Pyuria without symptoms (low positive predictive value) - Prophylactic culture in non-pregnant, non-procedure patients

### Interpreting Culture Results

| Colony Count | Clinical Significance |
|----|----|
| **\<10,000 CFU/mL** | Likely contamination |
| **10,000-100,000 CFU/mL** | Borderline; repeat if symptomatic |
| **\>100,000 CFU/mL single organism** | **UTI** (if symptoms present) |
| **Multiple organisms** | Likely contamination; repeat collection |

------------------------------------------------------------------------

## SECTION 7: CLINICAL PEARLS

✓ **Dipstick is SCREENING tool**, not diagnostic

✓ **Protein dipstick limited**: Albumin-specific; misses light chains, myoglobin

✓ **Always correlate dipstick with microscopy** (never interpret in isolation)

✓ **RBC casts = GLOMERULONEPHRITIS until proven otherwise** (urgent evaluation needed)

✓ **Hematuria without RBCs on microscopy** = hemoglobinuria or myoglobinuria (investigate further)

✓ **Contaminating epithelial cells** indicate improper collection; repeat if present

✓ **Orthostatic proteinuria benign** and requires no further workup once recognized

✓ **24-hour urine gold standard** but collection errors common; spot ACR acceptable alternative

✓ **Asymptomatic bacteriuria treatment NOT recommended** except in pregnancy

✓ **Urine culture only helpful if symptoms present** (high contamination rates in screening)

------------------------------------------------------------------------

## PRACTICE QUESTIONS

**Question 1**: A 28-year-old woman presents with dysuria. Urinalysis shows: dipstick trace protein, 2+ blood, LE+, nitrites+. Microscopy: 15 RBCs/lpf, 25 WBCs/lpf, 1 RBC cast, gram-negative rods. What is your NEXT step?

1.  Prescribe empiric nitrofurantoin for UTI
2.  Order blood cultures
3.  Refer for urgent kidney biopsy
4.  Send urine culture; repeat UA in 1 week

**Answer**: **C** - **RBC CASTS = GLOMERULONEPHRITIS**. This is NOT simple cystitis. The presence of RBC casts indicates glomerular disease (possibly IgAN, post-infectious GN, lupus, vasculitis). While LE+ and nitrites suggest bacterial infection, the RBC casts override this interpretation. She needs: - Urgent nephrology referral - Kidney biopsy for definitive diagnosis - Serologies (ANA, ANCA, anti-GBM, complement) - Blood cultures only if septic appearance

------------------------------------------------------------------------

**Question 2**: A 35-year-old man with fever (102°F), flank pain, and dysuria presents with UA showing: dipstick 3+ blood, LE+, WBCs 50/lpf, bacteria abundant. Microscopy shows isomorphic RBCs, WBCs, no casts. Which diagnosis is MOST likely?

1.  Acute glomerulonephritis
2.  Acute pyelonephritis
3.  Rhabdomyolysis
4.  Hemolytic anemia

**Answer**: **B** - **Pyelonephritis**. The key findings: - Isomorphic RBCs favor a nonglomerular source but do not exclude glomerular disease; integrate proteinuria, casts, kidney function, and urologic risk - Absence of RBC casts does not exclude glomerulonephritis; in this vignette, fever, flank pain, pyuria, and bacteriuria favor pyelonephritis - Abundant bacteria + LE+ + WBC + fever + flank pain = **PYELONEPHRITIS** - Management: Blood cultures, urine culture, empiric antibiotics (fluoroquinolone or cephalosporin)

------------------------------------------------------------------------

**Question 3**: A 65-year-old woman with CKD Stage 4 has routine UA showing: 2+ protein, trace blood. Microscopy: 2 RBCs/lpf, no casts. What action is MOST appropriate?

1.  Start ACE-inhibitor and recheck UA in 3 months
2.  Urgent kidney biopsy
3.  Refer for dialysis
4.  Quantify with spot ACR/PCR; monitor CKD with regular labs

**Answer**: **D** - **Proteinuria in CKD requires QUANTIFICATION, not just dipstick grading**. The trace blood with normal RBC count (no casts) is NOT concerning for glomerulonephritis. Management: - Spot ACR or 24-hour urine PCR to assess protein burden - Blood pressure control, ACE-I/ARB if proteinuric - Monitor eGFR slope - Biopsy only if atypical features (sudden worsening, active urinary sediment with casts)

------------------------------------------------------------------------

## KEY TAKEAWAYS

✓ **Dipstick is screening tool** with significant limitations; correlate with microscopy

✓ **RBC casts ALWAYS abnormal** = glomerulonephritis (urgent evaluation)

✓ **Hematuria without RBCs** = hemoglobinuria or myoglobinuria (investigate further)

✓ **Proteinuria requires quantification** with ACR/PCR (dipstick insufficient)

✓ **Bence Jones proteins missed by dipstick** = risk in myeloma patients

✓ **Orthostatic proteinuria benign** once recognized; no further workup

✓ **Contamination common** with improper collection; repeat if epithelial cells abundant

✓ **Culture only helpful if symptoms present** (high false-positive rate in asymptomatic patients)

✓ **Pyuria without bacteriuria** suggests non-infectious causes (interstitial nephritis, GN)

✓ **Always interpret UA in clinical context** (symptoms, vitals, other lab findings)

------------------------------------------------------------------------

## RELATED CLINICAL NOTES

- Urinary Tract Infection - UTI diagnosis and treatment
- Glomerulonephritis - GN classification and workup
- Hematuria Evaluation - Detailed hematuria workup
- Proteinuria Management - Proteinuria monitoring

------------------------------------------------------------------------

*This handout is designed for PA/medical student education. Always consult institutional protocols and clinical context for patient management.*

### Also on this topic

The same subject at other levels of depth.

- **Lecture:** [🔬 Urinalysis Interpretation](https://urinenephrology.org/2025_UDPA_Lectures_Live/urinalysis/interpretation.html)


---

[Website version](https://urinenephrology.org/student-resources/uti/urinalysis-student-handout.html) · Markdown synchronized October 3, 2026.