WBC/UA

Leukocytes in Urine

Análisis de orina

Última revisión: 7 de abril de 2026. Enfoque de fuentes: contexto estándar de interpretación de laboratorio, material médico de referencia y orientación clínica o de salud pública cuando corresponde.

¿Qué es Leukocytes in Urine?

Leukocytes, or white blood cells, in urine indicate the presence of an immune response within the urinary tract. While a few white blood cells can normally be found in urine, elevated numbers—a condition called pyuria—typically signal infection, inflammation, or irritation somewhere along the urinary system. The most commonly detected type is the neutrophil, which is the body's first-line defender against bacterial infections. Leukocytes in urine are detected through both microscopic examination (counting cells per high-power field) and through the leukocyte esterase test on a urine dipstick.

The leukocyte esterase dipstick test detects an enzyme released by neutrophils and is a highly sensitive screening tool for urinary tract infections. When combined with the nitrite test, positive leukocyte esterase results have strong predictive value for UTI. However, leukocytes can be present in urine for reasons other than bacterial infection, including kidney stones, interstitial nephritis, glomerulonephritis, and bladder tumors. The combination of findings from the complete urinalysis helps narrow the differential diagnosis and guide further testing.

Por qué importa

Leukocytes in urine are the most sensitive indicator of urinary tract inflammation and infection. Urinary tract infections affect approximately 150 million people worldwide each year, and the detection of pyuria is central to their diagnosis and management. Beyond infection, persistent sterile pyuria (leukocytes without bacteria) can be a clue to more serious conditions including kidney disease, tuberculosis of the urinary tract, or urologic malignancy. In hospitalized and catheterized patients, monitoring urine leukocytes helps guide antibiotic therapy and distinguish between true infection and colonization.

Rangos de referencia normales

GrupoRangoUnidad
Microscopic exam0–5WBC/HPF
Dipstick (leukocyte esterase)Negative

Los rangos de referencia pueden variar entre laboratorios. Compara siempre tus resultados con los rangos proporcionados por tu laboratorio.

Qué significan los niveles altos de WBC/UA

Causas comunes

  • Urinary tract infection (most common cause)
  • Kidney infection (pyelonephritis)
  • Kidney stones
  • Interstitial nephritis (drug-induced or autoimmune)
  • Glomerulonephritis
  • Bladder cancer or other urologic malignancy
  • Sexually transmitted infections (chlamydia, gonorrhea)
  • Prostatitis in men

Posibles síntomas

  • Painful or burning urination
  • Increased urinary frequency and urgency
  • Cloudy or milky urine
  • Foul-smelling urine
  • Pelvic or lower back pain
  • Fever and chills (if kidney infection)
  • Blood in urine

Qué hacer: Elevated leukocytes with bacteria and symptoms point toward a UTI requiring antibiotic treatment. A urine culture should be obtained to identify the causative organism and guide antibiotic selection. If leukocytes are elevated but cultures are negative (sterile pyuria), further investigation is needed—this may include testing for sexually transmitted infections, tuberculosis culture, imaging of the urinary tract, or referral to a urologist or nephrologist depending on the clinical scenario.

Qué significan los niveles bajos de WBC/UA

Causas comunes

  • Normal finding—healthy urine should contain very few white blood cells
  • Successful treatment of a urinary tract infection
  • Resolution of kidney or bladder inflammation

Posibles síntomas

  • No symptoms—few or no leukocytes is the normal expected result

Qué hacer: A normal leukocyte count in urine requires no further action. If this result follows treatment for a UTI, it confirms successful resolution of the infection.

¿Cuándo se recomienda la prueba de WBC/UA?

  • When UTI symptoms are present (pain, urgency, frequency)
  • As part of a routine urinalysis
  • When monitoring response to antibiotic therapy for UTI
  • In the evaluation of unexplained fever
  • When kidney stones or kidney disease is suspected
  • During pregnancy screening

Preguntas frecuentes

While a negative leukocyte esterase test makes a UTI less likely, it does not completely rule one out. False-negative results can occur if the urine is very dilute, if the infection is in its very early stages, or if the patient is immunocompromised with reduced white blood cell production. Some organisms like Chlamydia or Mycoplasma may cause urethritis without triggering a strong neutrophil response. If you have persistent UTI symptoms despite a negative leukocyte test, your doctor may order a urine culture, which is more definitive.
Sterile pyuria refers to the finding of elevated white blood cells in urine without bacterial growth on standard urine culture. It occurs in about 13% of patients with pyuria and has a broad differential diagnosis. Causes include sexually transmitted infections (which require specialized cultures), urinary tuberculosis, kidney stones, interstitial nephritis from medications (especially NSAIDs and antibiotics), autoimmune conditions like lupus nephritis, polycystic kidney disease, and bladder cancer. Prior antibiotic use can also create sterile pyuria by suppressing but not fully eliminating an infection.
The dipstick leukocyte esterase test and microscopic WBC count measure different things. The dipstick detects an enzyme released by white blood cells, including cells that have lysed (broken open) and are no longer visible under the microscope. This means the dipstick can be positive even when few intact cells are seen microscopically, especially in dilute or alkaline urine where cells degrade quickly. Conversely, the dipstick may be negative when white blood cells are present but have not released enough enzyme. Microscopic examination provides more precise information, while the dipstick is useful as a rapid screening tool.

Biomarcadores relacionados

BactBacteria in UrineNitNitrites in UrineRBC/UABlood in UrineWBCGlóbulos blancos

Referencias y enfoque de revisión

Las páginas del glosario de biomarcadores son explicaciones educativas y deben interpretarse junto con los rangos de referencia y comentarios proporcionados por tu laboratorio y tu profesional de salud. Para conocer nuestros estándares editoriales y proceso de revisión, consulta nuestra Política editorial y nuestro Proceso de revisión de contenido.

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Aviso médico: Esta información es solo educativa y no sustituye el consejo, diagnóstico ni tratamiento médico profesional. Los rangos de referencia pueden variar entre laboratorios. Consulta siempre a tu profesional sanitario para interpretar tus resultados concretos.

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