Pyuria
DEFINITION
WBCs (i.e., neutrophils,
eosinophils, monocytes, lymphocytes, or plasma cells) in urine.
More than 5 WBCs per
high-power field is generally considered abnormal, but the number of WBCs
found in urinary sediment varies with the method of collection, sample
volume and concentration, degree of cellular destruction after collection,
and laboratory technique.
PATHOPHYSIOLOGY
Large numbers of WBCs in
voided urine samples indicate active inflammation somewhere along the
urogenital tract.
Can be associated with
any pathologic process (infectious or non-infectious) that causes cellular
injury or death; tissue damage evokes exudative inflammation characterized
by evidence of leukocytic extravasation (pyuria) and increased vascular
permeability (hematuria and proteinuria).
SYSTEMS AFFECTED
Renal/Urologic—urethra, urinary bladder, ureters, and
kidneys
Genital—prepuce, prostate, vagina, and uterus
SIGNALMENT
Dog and cat
SIGNS
General Comments
Inflammation can cause
clinical signs localized to the site(s) of injury or may be accompanied by
systemic manifestations. Historical and physical examination findings
depend on the underlying cause, organ(s) affected, degree of organ
dysfunction, and magnitude of systemic inflammatory responses.
Non-obstructive lesions
confined to the urinary bladder, urethra, vagina, or prepuce rarely cause
systemic signs of inflammation. Systemic signs may accompany generalized
inflammatory lesions of the kidneys, prostate, or uterus.
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Physical Examination Findings
Local Effects of
Inflammation
Erythema of mucosal
surfaces—e.g., redness of vaginal or preputial mucosa
Tissue swelling—e.g.,
renomegaly, prostatomegaly, mural thickening of urinary bladder or urethra
Exudation of leukocytes
and protein-rich fluid—e.g., pyuria, purulent urethral or vaginal
discharge, pyometra, or prostatic abscess
Pain—e.g., adverse
response to palpation, dysuria, pollakiuria, stranguria
Loss of function—e.g.,
polyuria, dysuria, pollakiuria, urinary incontinence
Systemic Effects of
Inflammation
·
Fever
·
Depression
·
Anorexia
·
Dehydration
CAUSES
Kidney
Pyelonephritis—e.g.,
bacterial, fungal, parasitic, or mycoplasmal
Nephrolith(s)
Neoplasia
Trauma
Immune-mediated
Ureter
Ureteritis—e.g., bacterial
Ureterolith(s)
Neoplasia
Urinary Bladder
Cystitis—e.g., bacterial, mycoplasmal, fungal, or parasitic
Urocystolith(s)
Neoplasia
Trauma
Overdistension—urethral obstruction
Pharmacologic—cyclophosphamide
Urethra
Urethritis—e.g., bacterial, fungal, or mycoplasmal
Urethrolith(s)
Neoplasia
Trauma
Foreign body
Prostate
Prostatitis/abscess—e.g.,
bacterial or fungal
Neoplasia
Penis/Prepuce
Balanoposthitis
Neoplasia
Foreign body
Uterus
Pyometra/metritis—e.g.,
bacterial
Vagina
Vaginitis—bacterial,
mycoplasmal, viral, or fungal
Neoplasia
Foreign body
Trauma
RISK FACTORS
Any disease process, diagnostic procedure, or therapy that
alters normal host urinary tract defenses and predisposes to infection.
Any disease process, dietary factor, or therapy that
predisposes to the formation of metabolic uroliths.
DIAGNOSIS
DIFFERENTIAL DIAGNOSIS
Voided Specimens
Rule out vaginitis—signs
include vaginal discharge, erythema of vaginal mucosa, licking of the
vulva, and attracting male dogs.
Rule out pyometra,
metritis—signs include vaginal discharge, large uterus, pyrexia, depression,
anorexia, polyuria, polydipsia, and a recent history of estrus,
parturition, or progestin administration.
Rule out
balanoposthitis—signs include preputial discharge, erythema of preputial
or penile mucosa, and licking of the prepuce.
Rule out prostatitis,
prostatic abscess, or prostatic neoplasia—signs include urethral
discharge, prostatomegaly, pyrexia, depression, dysuria, tenesmus, caudal
abdominal pain, and stiff gait.
Rule out urethritis,
urethroliths, urethral neoplasms—signs include dysuria, pollakiuria,
stranguria, and/or palpable uroliths or mass lesions in the urethra.
Rule out inflammatory
disorders of urinary bladder and kidneys.
Specimens Collected by
Cystocentesis
Rule out urethral
obstruction—signs include stranguria, anuria, and a large overdistended
urinary bladder.
Rule out prostatic and
urethral disorders (see above); purulent prostatic or urethral exudates
can reflux into the urinary bladder.
Rule out cystitis,
urocystoliths, and urinary bladder neoplasia—signs may include dysuria,
pollakiuria, stranguria, and/or palpable uroliths or mass lesions in the
urinary bladder.
Rule out
pyelonephritis—signs may include pyrexia, depression, anorexia, polyuria,
polydipsia, renal pain, and renomegaly.
Rule out post-traumatic
pyuria—signs may include the history of trauma, including iatrogenic
causes.
LABORATORY FINDINGS
Drugs That May Alter Laboratory Results
WBCs, lyse rapidly in hypotonic or alkaline urine.
Administration of alkalinizing agents (e.g., sodium bicarbonate, potassium
citrate, chlorothiazide, or acetazolamide) or agents that produce hypotonic
urine (e.g., diuretics and glucocorticoids) may falsely decrease urine WBC
numbers.
Leukocyte esterase reagent strip (dipstick) methods are not
recommended for use in canine (not sensitive) or feline (not specific) urine
samples. In addition, nitrofurantoin, cephalosporins, and gentamicin can cause
false-positive leukocyte esterase reactions.
Urinary WBC concentrations can be low in patients with
inflammatory disorders who have been given steroidal or nonsteroidal
anti-inflammatory drugs.
Disorders That May Alter Laboratory Results
Disorders associated with diminished WBC function or
absolute neutropenia can artificially lower WBC values.
Disorders associated with the production of hypotonic urine
or alkaline urine artificially lower WBC values.
Miscellaneous Factors That May Alter Laboratory Results
False-negative leukocyte esterase reaction in dogs when
urine is tested by the reagent strip (dipstick) method.
False-positive and false-negative leukocyte esterase
reaction in cats when urine is tested by the reagent strip (dipstick) method.
Valid if Run in Human Laboratory?
Valid if urinary sediment is examined microscopically;
invalid if only leukocyte esterase reagent strip (dipstick) method is used.
CBC/BIOCHEMISTRY/URINALYSIS
Pyuria in specimens collected by voiding, manual
compression, or transurethral catheterization indicates an inflammatory lesion
involving at least the urinary or genital tracts.
Pyuria in specimens collected by cystocentesis localizes the
site of inflammation to at least the urinary tract, but does not exclude the
urethra and genital tract. Reflux of prostatic exudates into the urinary
bladder may result in pyuria in patients with prostatic disease.
Pyuria associated with WBC casts is unequivocal evidence of
renal parenchymal inflammation.
Generalized renal injury may be associated with concomitant
leukocytosis, isosthenuria, and azotemia.
Pyuria associated with bacteria, fungi, or parasite ova in
sufficient numbers to be seen by microscopic sediment examination indicates
that the inflammatory lesion was caused or complicated by urinary tract
infection. Detection of bacteria in urine sediment by light microscopy may be
enhanced by placing a drop (20 μL) of urine sediment on a glass slide, allowing
it to dry without spreading, staining with Diff-Quik, and examining for
bacteria under oil immersion (1,000 ×).
Pyuria associated with neoplastic cells indicates neoplasia.
Diagnosis of urinary tract neoplasia by cytologic examination of urine may be
complicated by epithelial cell hyperplasia and atypia caused by urinary tract
inflammation or the physicochemical properties of urine (pH and tonicity
causing cell scalding).
OTHER LABORATORY TESTS
Perform quantitative urine culture on all patients with
pyuria; it provides the most definitive means of identifying and characterizing
bacterial urinary tract infection. It is important to note that the absence of
pyuria does not rule out the bacteriuria as patients with bacteriuria
frequently do not have pyuria.
Negative urine culture results suggest a non-infectious
cause of inflammation (e.g., uroliths, neoplasia) or inflammation associated
with urinary tract infection caused by fastidious organisms (e.g., mycoplasmas
and viruses) or by organisms capable of forming intracellular bacterial
colonies or biofilms. False-negative culture results may also be due to recent
antimicrobic therapy, sample mishandling, or delays between specimen collection
and culture.
Cytologic evaluation of urinary sediment, prostatic fluid,
urethral or vaginal discharges, or biopsy specimens obtained by catheter or
needle biopsy may help evaluate patients with localized urinary or genital
tract disease. Cytologic examination may establish a definitive diagnosis of
urinary tract neoplasia, but negative cytologic findings do not rule out
neoplasia.
IMAGING
Survey abdominal radiography, contrast urethrocystography
and cystography, urinary tract ultrasonography, and excretory urography are
important means of identifying and localizing underlying causes.
DIAGNOSTIC PROCEDURES
Urethrocystoscopy—indicated in patients with persistent
lesions of the lower urinary tract for which a definitive diagnosis has not
been established by other, less invasive, means.
Light microscopic evaluation of tissue specimens—indicated
in patients with lesions of the urinary or genital tracts for which a
definitive diagnosis has not been established by other, less invasive, means;
tissue specimens may be obtained by membrane disruption (traumatic)
catheterization biopsy, cystoscopy and forceps biopsy, or exploratory
laparotomy; aspiration and punch biopsy techniques may be used to evaluate the
prostate gland.
TREATMENT
Treatment varies, depending on the underlying cause and
specific organs involved.
Pyuria associated with systemic signs of illness (i.e.,
pyrexia, depression, anorexia, vomiting, dehydration, leukocytosis, polyuria,
and polydipsia) or urinary obstruction warrants aggressive diagnostic
evaluation and initiation of specific, supportive, and/or symptomatic
treatment.
MEDICATIONS
DRUG(S)
Depending on the underlying cause
CONTRAINDICATIONS
Avoid glucocorticoids or other immunosuppressive agents in
patients suspected of having urinary or genital tract infections.
Avoid potentially nephrotoxic drugs (e.g., gentamicin) in
febrile, dehydrated, or azotemic patients and those suspected of having
pyelonephritis, septicemia, or pre-existing renal disease.
FOLLOW-UP
PATIENT MONITORING
Response to treatment by serial urinalyses, including
examination of urine sediment; collect specimens from most patients by cystocentesis
to avoid contamination by preputial or vaginal exudates; perform transurethral
catheterization if the expected benefits outweigh the risk of iatrogenic
bacterial urinary tract infection.
POSSIBLE COMPLICATIONS
Infectious and non-infectious inflammatory disorders of the
urinary tract can cause primary renal failure, urinary obstruction, uremia,
septicemia, and death.
Pyuria is a potential risk factor for the formation of
matrix or matrix-crystalline urethral plugs and subsequent urethral obstruction
in male cats.
MISCELLANEOUS
ASSOCIATED CONDITIONS
Hematuria
Proteinuria
Bacteriuria
SYNONYMS
Leukocyturia
ABBREVIATION
WBC = white blood cell