Bedside Snapshot
- Normal Result
- WBC 0–5/hpf; RBC 0–2/hpf; hyaline casts 0–2/lpf; no other casts or tubular cells (lab-specific ranges).
- Significant Result
- RBC ≥3/hpf (microhematuria; see the boundary note in Reference & Critical Ranges), any RBC or WBC cast, numerous or coarse granular cast, waxy, broad or fatty cast, or renal tubular cells. No universal critical value.
- Positive Suggests
- RBC casts or dysmorphic RBCs: glomerulonephritis
- WBC casts: pyelonephritis or interstitial nephritis
- Pyuria with bacteria: cystitis or pyelonephritis
- Oval fat bodies: nephrotic-range proteinuria
- Negative Does Not Exclude
- Early or focal disease, stones and tumors, which can all leave the sediment normal. A dilute or delayed specimen can hide cells and casts; repeat on a fresh sample.
- Act Now If
- RBC casts, or dysmorphic RBCs with proteinuria, hypertension or rising creatinine: check BP, creatinine and urine protein; prompt nephrology referral.
- Watch Out For
- Dipstick blood with fewer than 3 RBC/hpf suggests hemoglobin or myoglobin, or lysed RBCs (dilute or alkaline urine, delayed exam). Repeat on a fresh specimen before calling it blood.
Reference & Critical Ranges
Lab-specific ranges: Every lab reports sediment its own way, with its own microscope and counting method. Your lab report's range wins. The values below are typical.
Reference ranges
| Element | Typical Result | Notes |
|---|---|---|
| WBCs | 0–5/hpf | Above the lab cutoff = pyuria |
| RBCs | 0–2/hpf | 3 or more/hpf = microhematuria at the AUA/SUFU reporting threshold. Statement 1 of the 2025 guideline says more than 3, but its body text uses 3 or more, so a count of exactly 3 is borderline. Use the lab cutoff. Critical Care Transport Table 9-3 gives ≤2/hpf; older emergency-medicine references accepted 2–3 (men) to 2–4 (women) and used 5/hpf as abnormal (Rosen's 8e Ch. 97), so 3–5/hpf may read as normal on an older interval yet still warrants AUA/SUFU evaluation. |
| Hyaline casts | 0–2/lpf | Occasional hyaline casts can be normal after exercise or dehydration |
| Other casts | None | WBC, RBC, waxy, broad and fatty casts are abnormal. Numerous or coarse granular casts are abnormal (muddy-brown casts suggest ATN); an occasional fine granular cast may be benign. |
| Renal tubular epithelial cells | None | Suggests tubular injury |
| Squamous epithelial cells | Few | Many = contaminated specimen; recollect |
| Bacteria | None to few | Interpret with WBCs, nitrite and culture |
| Crystals | Variable | Depends on urine pH and crystal type |
| Children | Lab pediatric interval | No separate sediment ranges verified for this page |
Severity & critical values
| Level | Finding | Meaning |
|---|---|---|
| Microhematuria | 3 or more RBC/hpf | Evaluate the source; a positive dipstick alone does not confirm it |
| Pyuria | More than 5 WBC/hpf (lab-specific) | Inflammation or infection; correlate with symptoms and culture |
| Urgent finding | RBC casts or WBC casts | Glomerular or renal parenchymal disease; needs prompt specialist review |
Critical values: There is no universal critical value for urine microscopy. The findings that need a specialist quickly are RBC and WBC casts.
Conversion: Nothing to convert here. Cells are counted per high-power field (hpf, 400×). Casts are counted per low-power field (lpf, 100×).
Causes of Abnormal Results
Positive result
| Cause | Clue |
|---|---|
| Glomerulonephritis (IgA, lupus, ANCA vasculitis, post-infectious) | RBC casts, dysmorphic RBCs, proteinuria, hypertension, reduced eGFR |
| Acute interstitial nephritis | WBC casts, pyuria without bacteria, recent NSAID, antibiotic or PPI exposure |
| Pyelonephritis | WBC casts, pyuria with bacteria, flank pain, fever |
| Cystitis, stone or lower-tract bleeding | Isomorphic RBCs (favor a non-glomerular source but do not exclude glomerular disease), pyuria with bacteria or crystals, dysuria, flank pain |
| Urologic malignancy (bladder, upper tract, kidney) | Persistent microhematuria or gross hematuria, smoking and other risk factors. A normal sediment does not exclude it; risk-based urologic evaluation is required (AUA/SUFU 2025) |
| Myoglobinuria or hemoglobinuria | Dipstick blood with no or few RBCs and dark urine; check CK for rhabdomyolysis (see the Myoglobin page) |
| Tubular injury (ATN, toxins) | Numerous or coarse granular casts, muddy-brown casts, renal tubular epithelial cells |
| Nephrotic-range proteinuria | Oval fat bodies and fatty casts (Maltese cross under polarized light) |
| Chronic kidney disease | Waxy and broad casts, a reduced eGFR |
| Sterile pyuria (TB, chlamydia, gonorrhea) | Pyuria with a negative standard culture; test for TB and STIs as the history suggests |
False positive vs true positive
- Vaginal or menstrual contamination: It adds WBCs and RBCs, so both counts climb. Many squamous cells confirm the contamination.
- Semen or recent sexual activity: Recent sex or semen puts WBCs in the sample, with no infection behind them.
- Exercise or catheter trauma: Exercise or catheter trauma leaves transient RBCs. They are usually isomorphic, with no casts.
- Crystals: Calcium oxalate and urate crystals can be normal. Refrigerated urine especially.
Crystals
| Crystal | Urine pH | Shape | Meaning |
|---|---|---|---|
| Uric acid | Acidic | Yellow-brown, diamond or rhomboid | Gout, tumor lysis, uric acid stones |
| Calcium oxalate | Acidic to neutral | Envelope (dihydrate), or dumbbell, oval or needle (monohydrate) | Often normal. Monohydrate is the form classically seen in ethylene glycol poisoning, but it supports the diagnosis only with acidosis and an osmolal gap |
| Triple phosphate (struvite) | Alkaline | "Coffin lid" shape | Urease-producing organisms (Proteus, Klebsiella) and staghorn stones |
| Cystine | Acidic | Hexagonal plates | Cystinuria |
Interpretation & Bedside Approach
Step-by-step approach
- Is the specimen valid? Check the collection method (clean-catch midstream, discarding the first 10 mL per AUA/SUFU guidance), the squamous cell count and the time to the lab.
- Does the dipstick agree? Few RBCs with a positive dipstick points to hemoglobin or myoglobin. Microscopy is what confirms true hematuria.
- Quantify and confirm: 3 or more RBC/hpf on one properly collected specimen meets the AUA/SUFU definition. Their summary statement says more than 3, so a count of exactly 3 is borderline. For pyuria, use the lab cutoff.
- Locate the source: RBC casts and dysmorphic RBCs point to glomerular bleeding. Isomorphic RBCs lean toward a non-glomerular source, but they do not rule out glomerular disease. Read them with casts, proteinuria and eGFR.
- Correlate with symptoms and culture: Pyuria with symptoms supports a UTI. Pyuria by itself does not establish one.
- Escalate or dispose: Casts or a glomerular pattern call for kidney function tests and nephrology review. Microhematuria calls for a risk-based workup under the AUA/SUFU guideline.
Pattern & what it suggests
| Pattern | Suggests |
|---|---|
| RBC casts | Glomerular bleeding; glomerulonephritis is the working diagnosis |
| Dysmorphic RBCs plus proteinuria | May indicate glomerular disease (AUA/SUFU 2025) |
| Isomorphic RBCs, no casts | Favors a lower-tract, stone or malignant source; does not exclude glomerular disease. Malignancy screen per AUA/SUFU |
| WBC casts | Pyelonephritis or interstitial nephritis |
| Pyuria with bacteria and symptoms | Cystitis or pyelonephritis; send culture |
| Pyuria without bacteria | Sterile pyuria: TB, STI, stones, recent antibiotics, interstitial nephritis |
| Granular or renal tubular epithelial cells | Tubular injury (ATN) |
| Oval fat bodies, fatty casts | Nephrotic-range proteinuria |
Reading dysmorphic RBCs takes phase-contrast or a careful look at shape. Nobody agrees on a cutoff. Studies report anything from about 10% to 90% dysmorphic RBCs. Gaggar and Raju suggest 40% or more dysmorphic RBCs and/or 5% or more acanthocytes as a glomerular definition, though there is no consensus on it. Go by the lab's cutoff, and read the count with casts and proteinuria.
Dipstick vs microscopy: A positive dipstick is the cue to run microscopy, not a substitute for it. The strip cannot name the cast type or the RBC shape.
Special Populations
| Population | What Changes | Clinical Implication |
|---|---|---|
| Neonates & infants | Bag specimens are often contaminated | Contaminated samples cause false pyuria and bacteriuria. A bag specimen cannot confirm UTI; in febrile infants, diagnosis needs an abnormal urinalysis plus a significant culture from a catheter or suprapubic specimen |
| Children & adolescents | The AUA/SUFU microhematuria thresholds are adult guidance. No separate sediment ranges verified for this page | Use the lab's pediatric interval and interpret casts and RBCs in clinical context. In febrile young children, UTI diagnosis needs an abnormal urinalysis and a culture from a catheter or suprapubic specimen, not a bag |
| Pregnancy | Bacteriuria screening is recommended | IDSA 2019 (strong recommendation): screen for and treat asymptomatic bacteriuria in pregnancy |
| Older adults | Pyuria and bacteriuria are common without symptoms | Do not treat sediment findings alone; IDSA 2019 advises against screening most functionally impaired older adults |
| CKD & dialysis | Baseline sediment may already be abnormal | Compare with prior sediment; a new cast or a new dysmorphic RBC pattern matters more than a single finding |
| Athletes | Exercise can cause transient RBCs | Repeat the test after rest before pursuing an extensive workup |
Interfering Factors & Pitfalls
Collection & handling
| Factor | Effect | Why | Avoid / Fix |
|---|---|---|---|
| Delayed examination | ↓ cells and casts (False −) | Cell lysis and cast dissolution | Examine promptly within the lab time limit. The 2024 review by Gaggar and Raju cites about 1 hour at room temperature or up to 4 hours refrigerated |
| Vaginal, menstrual or skin contamination | ↑ WBC and RBC (False +) | Genital and skin cells and blood enter the sample | Clean-catch midstream; recollect when squamous cells are many |
| Dilute or hypotonic urine | ↓ casts and cells (False −) | Low concentration; RBCs lyse | Repeat on a first-morning specimen |
| Alkaline urine | RBC lysis (False −) | RBCs lyse at alkaline pH; the dipstick can still be positive | Read a fresh sample; compare with the dipstick |
| Refrigeration | ↑ crystals (False +) | Urate and phosphate crystals precipitate on cooling | Note storage conditions; interpret crystals at room temperature |
Medications & substances
| Drug | Effect | Why | Avoid / Fix |
|---|---|---|---|
| Anticoagulants (warfarin, DOACs) | ↑ hematuria | Bleeding from the urinary tract | Still evaluate hematuria; do not attribute it to the drug without workup |
| Cyclophosphamide | ↑ RBC | Hemorrhagic cystitis | Review drug history |
| NSAIDs, penicillins, cephalosporins, sulfonamides, rifampin, PPIs | ↑ WBC and WBC casts | Interstitial nephritis | Review recent drug exposure |
| Acyclovir, indinavir, sulfadiazine, methotrexate | ↑ crystals | Drug crystal precipitation | Include drug crystals in the differential |
Assay & device
- Automated analyzers: can miss casts, crystals and dysmorphic RBCs (False −). When those findings matter, someone has to look under the microscope.
- Dipstick blood with few RBCs: points to hemoglobin or myoglobin, not hematuria (False + for hematuria).
Common misinterpretations
- Microscopy has to confirm a positive dipstick before it counts as hematuria (AUA/SUFU 2025).
- Occasional hyaline casts are usually not disease. Waxy, broad, fatty, RBC and WBC casts are all abnormal, and so are numerous or coarse granular ones.
- Calcium oxalate crystals do not prove ethylene glycol poisoning on their own. Move to the toxic-alcohols workflow.
- A clean sediment does not rule out early glomerular disease.
Physiology & Test Basics
What it measures
Urine microscopy spins the urine down, then identifies and counts cells, casts, crystals and organisms in the sediment. This page covers only the microscopic sediment. The dipstick and the culture are separate tests on the urinalysis panel.
Physiology & regulation
- Casts form in the renal tubules out of Tamm-Horsfall protein. High osmolality and low urine pH favor them.
- RBC casts form once red cells leak through damaged glomerular capillaries and into the tubule.
- Epithelial cells show where they came from. Squamous cells shed from the distal urethra or vagina. Transitional cells shed from the bladder and ureters. Renal tubular cells shed from the kidney.
- Dysmorphic RBCs get altered passing through a damaged glomerulus. Isomorphic RBCs do not.
How it is measured
Start with a fresh clean-catch midstream sample (discard the first 10 mL) or a catheter sample. Spin the urine down, then read the sediment on a slide: cells at 400× (hpf), casts at 100× (lpf). Phase-contrast is the tool for RBC shape. Look at it promptly. The 2024 review by Gaggar and Raju cites about 1 hour at room temperature or up to 4 hours refrigerated. The lab sets its own limit.
Why it matters
Microscopy sorts glomerular bleeding from lower-tract and interstitial causes of hematuria and pyuria. It also finds casts the dipstick cannot see. In acute care, that helps you decide whether the patient needs nephrology, urology or an infection workup.
Clinical Pearls
RBC casts point to glomerular disease: RBC casts are specific for bleeding inside the nephron. They should send you toward kidney function tests and nephrology review.
Dysmorphic RBCs plus proteinuria: That combination, with hypertension or a reduced eGFR, may point to glomerular disease (AUA/SUFU 2025).
Hyaline casts can be normal: A few hyaline casts after exercise, dehydration or fever are common, even in healthy people.
Calcium oxalate supports, but does not prove, ethylene glycol poisoning: Crystals only support the diagnosis when acidosis and an osmolal gap are both present. Manage per the toxic-alcohols workflow. Crystals alone are not enough.
Do not treat pyuria alone: IDSA 2019 says pyuria cannot reliably tell asymptomatic bacteriuria from a symptomatic UTI. The same guideline advises against screening most adults outside pregnancy and select procedures.
EMS and transport: Write the collection time on the specimen. Microscopy only holds up inside the lab's time limit. A long transport can turn a normal result into a meaningless one.
References
- Barocas DA, Boorjian S, Alvarez R, et al. Microhematuria: AUA/SUFU Guideline (2020, amended 2025). American Urological Association; February 2025. https://www.auanet.org/documents/Guidelines/PDF/2025%20Guidelines/MH%20Unabridged%20FINAL.pdf
- Nicolle LE, Gupta K, Bradley SF, et al. Clinical practice guideline for the management of asymptomatic bacteriuria: 2019 update by the Infectious Diseases Society of America. Clin Infect Dis. 2019;68(10):e83–e110. https://doi.org/10.1093/cid/ciy1121
- KDIGO Glomerular Diseases Work Group. KDIGO 2021 clinical practice guideline for the management of glomerular diseases. Kidney Int. 2021;100(4S):S1–S276. https://doi.org/10.1016/j.kint.2021.05.021
- Gaggar P, Raju SB. Diagnostic utility of urine microscopy in kidney diseases. Indian J Nephrol. 2024;34(3):213–221. https://doi.org/10.25259/ijn_362_23
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