Infection/Inflammation Detector in Urine
White blood cells in urine (pyuria) mean your immune system is fighting something in the urinary tract. Usually it's a UTI, but sterile pyuria (WBCs without bacteria) can indicate kidney disease, kidney stones, STIs, or interstitial nephritis.
What is Urine WBC (Pyuria)?
Dipstick detects leukocyte esterase (enzyme from WBCs). Microscopy: >5 WBC/HPF is significant. Pyuria + bacteriuria = UTI. Pyuria without bacteriuria = sterile pyuria (needs further evaluation).
↑ What High Urine WBC (Pyuria) Means
Inflammation or infection in the urinary tract. Most commonly UTI. Sterile pyuria (no bacteria): consider STI (chlamydia), interstitial nephritis, kidney stones, TB, or contamination.
Common symptoms:
If UTI: dysuria (painful urination), frequency, urgency, suprapubic pain · If pyelonephritis: fever, flank pain, nausea · If STI: urethral discharge, dysuria
↓ What Low Urine WBC (Pyuria) Means
N/A.
Common symptoms:
N/A
Why It Matters
When normal:
Screens for UTI (with nitrites)
Sterile pyuria triggers important differential diagnosis
Monitors UTI treatment response
Risks if abnormal:
UTI if combined with bacteriuria and symptoms
Sterile pyuria: may indicate STI, interstitial nephritis, or TB
What Can Cause Abnormal Levels?
Urinary Tract Infection
55% likelyMost common cause. Confirmed by positive culture with >100,000 CFU/mL.
Contamination
25% likelyVaginal contamination is common. Clean-catch midstream technique reduces this.
STI (sterile pyuria)
Chlamydia and gonorrhea cause urethritis with pyuria but negative standard culture.
Interstitial Nephritis
Drug-induced (NSAIDs, antibiotics) or autoimmune. WBC casts are characteristic.
Kidney Stones
Stones cause local inflammation and pyuria.
Renal Tuberculosis
Classic sterile pyuria—acid-fast bacilli cause pyuria without standard bacterial growth.
What You Can Do
If symptomatic + pyuria: urine culture to confirm UTI
Impact: Guides antibiotic selection \u00B7 Timeline: Before antibiotics
Proper clean-catch technique to avoid contamination
Impact: Reduces false positives \u00B7 Timeline: At collection
If lifestyle changes aren't enough:
If sterile pyuria: test for STIs (chlamydia/gonorrhea NAAT)
Impact: Common cause of sterile pyuria in young adults \u00B7 Timeline: One-time
If persistent sterile pyuria: consider interstitial nephritis, TB, or kidney stones
Impact: Expanded workup \u00B7 Timeline: As needed
Recommended retest: After completing antibiotics to confirm clearance
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