Christina Carpenter, MD
Mark L. Jordan, MD, FACS
BASICS
DESCRIPTION
• Presence of WBCs in the urine
• Normal #WBCs in a urine specimen
– Men ≤2 WBC/hpf
– Women ≤5 WBC/hpf
• When seen with bacteriuria, suggests inflammatory response of urothelium (ie, infection)
• When seen without bacteriuria (sterile pyuria), raises suspicion for tuberculosis, partially treated UTI, stones, and/or malignancy
EPIDEMIOLOGY
When seen in a voided urine specimen, has an 80–95% sensitivity for detecting patients with a urinary tract infection (UTI)
RISK FACTORS
• Urolithiasis
• Previous UTI
• Sexually transmitted disease
• Malignancy
PATHOPHYSIOLOGY
• Clean-catch midstream urine may contain contaminants (bacteria, squamous epithelial cells)
• Significant pyuria (at least 10 WBCs/mm3) is uncommonly seen in patients without true infection
ALERT
60% of elderly women have significant pyuria without associated bacteriuria (1)[A].
• Can be caused by bacteria in the urinary tract provoking an inflammatory response
• Bacteria can colonize the genitourinary system in a retrograde fashion
• Certain bacteria are more frequently the cause of UTIs as they are more efficient at adhering to the mucosal cells of the urinary tract (eg, Escherichia coli)
ASSOCIATED CONDITIONS
• Bacteriuria
• UTI
• Pyelonephritis
• Nephrolithiasis
GENERAL PREVENTION
• Proper toileting habits
• Complete bladder emptying
• Adequate fluid intake (stone prevention)
DIAGNOSIS
HISTORY
• Common symptoms: Dysuria, frequency, urgency, malaise
• Fever (more common with upper tract infection)
• Hematuria (gross)
– Occasional
– More common in females
– Rare in children
• Atypical presentations
– Young patients
Difficulty with toilet training, urgency, incontinence
Abdominal discomfort, failure to thrive, fever, vomiting, jaundice
– Elderly
Incontinence, fevers, frequency, urgency
May be asymptomatic
• History of recurrent childhood fevers—may imply frequent UTIs and potential congenital anomalies
• History of UTIs among female family members
PHYSICAL EXAM
• Suprapubic tenderness
• Costovertebral angle tenderness
• Fever
• Children—may have abdominal discomfort, tenderness, and/or distention
DIAGNOSTIC TESTS & INTERPRETATION
Lab
• Dipstick
– Best screening tool
– Leukocyte esterase (LE)
Produced by granulocytes that catalyze the hydrolysis of an indoxylcarbonic acid ester to indoxyl, which reacts with a diazonium salt to produce a purple color on the reagent strip
75–96% sensitive for a culture-positive UTI (2)[A]
Sterile pyuria
Produces positive LE test with negative culture
Disease process without bacteriuria
Causes of false negatives
RBC >10 K/μL
Glucose >1 g/dL
Albumin >500 mg/dL
Formaldehyde
Medications: Cephalexin, gentamicin, tetracycline
Causes of false positives
Specimen contamination
Recent instrumentation of GU tract
Medications: Imipenem, meropenem, clavulanic acid
– Presence of nitrites, blood, or protein suggests UTI
• Microscopic analysis—can see crystals and/or bacteria
• Gram stain—can identify type of bacteria
• Culture
– Clean-catch midstream specimen = most common
– Catheterized urine—required in situations in which patients are unable to collect specimen (children, incontinent adults, obese population, patients in urinary retention)
– Segmented urine specimen
Sequential voided urine samples aimed to localize infection/inflammation source
Stamey test (see Stamey test [Three-glass test, Four-glass tests, Meares-Stamey Test])
• AFB culture—if patient has history of and/or possible exposure to TB
• Rapid in-office microbiology testing
– 80% accurate for detecting, quantifying, and identifying specific bacteria in urine
– Usually performed on a fresh unspun sample
• Urine cytology—if malignancy is suspected
Imaging
• Children: Ultrasound, VCUG, radionuclide cystogram, IV pyelogram
• Adult: Indicated only in the setting of suspected pathology, obstruction, stone disease, and/or hematuria
• Sterile pyuria: Imaging to identify source/evaluate cause
Diagnostic Procedures/Surgery
• Localization of bacteria
– Segmented urine specimen
– Ureteral catheterization in OR
– Immunologic/antibody studies
• Isotopic function studies
• Cystogram
• CT: Localization of nidus/abnormality responsible for bacteriuria/pyuria (ie, abscess)
• Cystoscopy—indicated for symptomatic patients with persistent pyuria and negative urine cultures (3)[A]
DIFFERENTIAL DIAGNOSIS
• Specimen contamination
• Cystitis
• Epididymitis
• Pyelonephritis—acute, chronic, emphysematous, tuberculous, xanthogranulomatous
• Genitourinary TB
• Interstitial cystitis
• Interstitial nephritis
• Neoplasm
– Urothelial carcinoma
– Renal cell carcinoma
• Prostatitis
• Renal abscess
• Periurethral abscess
• STI/STD
• Renal transplant rejection
• Urethral diverticulum
• Urethritis
• Foreign bodies in GU tract (stents, catheters)
• Urinary tract fistula
• Vulvovaginitis
• Kawasaki disease
TREATMENT
GENERAL MEASURES
• Identify cause of inflammatory response
• Direct treatment at cause of pyuria
• UTI is most commonly the origin
MEDICATION
First Line
• In infection, should be empiric until targeted therapy can be initiated based on culture results (4)
• See “Urinary tract infection (UTI), adult female,” “Urinary tract infection (UTI), adult male” and “Urinary tract infection (UTI), pediatric”
Second Line
N/A
SURGERY/OTHER PROCEDURES
• Correct underlying abnormality
• Treat calculus
• Remove foreign body (eg, ureteral stent)
ADDITIONAL TREATMENT
• Bacteriuria with pyuria is treated as a UTI in children and premenopausal women
• Persistent or recurrent bacteriuria may require prolonged antibiotic treatment followed by chronic low-dose prophylactic antibiosis
• High-risk patients (children with congenital abnormalities, immunocompromised adults) may need chronic suppressive antibiotic treatment
• Postmenopausal women
– May have chronic pyuria with mild bacteriuria
Require treatment only if symptomatic or if associated with complicating factors
• Diabetics, patients with obstructive uropathy, and immunocompromised patients may have additional requirements to address ongoing pyuria adequately
ONGOING CARE
PROGNOSIS
Dependent upon etiology
COMPLICATIONS
• Ascending bacterial infections
• Urosepsis
• Renal failure
• Death
FOLLOW-UP
Patient Monitoring
• Repeat exam 2-wk post-UTI treatment
– Urinalysis, urine culture
– Reassess symptoms
• Routine periodic evaluation to check for recurrence of pyuria
Patient Resources
www.UrologyHealth.org
REFERENCES
1. Boscia JA, Kaye D. Asymptomatic bacteriuria in the elderly. Infect Dis Clin North Am. 1987;1:893–905.
2. Drekonja DM, Johnson JR. Urinary tract infections. Prim Care. 2008;35:345–367.
3. Dielubanza EJ, Schaeffer AJ. Urinary tract infections in women. Med Clin North Am. 2011;95:27–41.
4. Schaeffer AJ, Schaeffer EM. Infections of the urinary tract. In: Wein AJ, Kavoussi LR, Novick AC, et al. Campbell-Walsh Urology. 10th ed. Philadelphia, PA: Elsevier Saunders; 2012.
ADDITIONAL READING
• Abrahamian FM, Moran GJ, Talan DA. Urinary tract infections in the emergency department. Infect Dis Clin North Am. 2008;22:73–87.
• Lin KW, Brown T. Screening for asymptomatic bacteriuria in adults. Am Fam Physician. 2010;81:508.
• Mulvey MA. Adhesion and entry of uropathogenic Escherichia coli. Cell Microbiol. 2002;4:257–271.
See Also (Topic, Algorithm, Media)
• Bacteriuria
• Pyelonephritis, Chronic
• Pyelonephritis, Emphysematous
• Pyelonephritis, Xanthogranulomatous
• Prostatitis, Chronic, Bacterial
• Prostatitis, Chronic, Nonbacterial, Inflammatory
• Prostatitis, General
• Pyuria Algorithm 
• Pyuria, Image 
• Tuberculosis, Genitourinary
• Urinary Tract Infection (UTI), Adult Female
• Urinary Tract Infection (UTI), Adult Male
• Urinary Tract Infection (UTI), Pediatric
CODES
ICD9
791.9 Other nonspecific findings on examination of urine
ICD10
N39.0 Urinary tract infection, site not specified
CLINICAL/SURGICAL PEARLS
• Absence of pyuria should lead the clinician to question a diagnosis of UTI.
• Sterile pyuria does not suggest a benign process.
• Persistent symptomatic pyuria requires further workup, ie, cystoscopy, imaging.
• Atypical presentations in children, the elderly, and the immunocompromised require the clinician to maintain a high index of suspicion.