Check for pseudohematuria
A negative urine dipstick result for blood with a concurrent negative result for bilirubin from a patient with discolored
urine warrants testing a second urine sample in case RBCs are only intermittently present. If the second sample's dipstick
or sediment examination results remain negative for RBCs, consider pseudohematuria—urine discoloration from pigments derived
from drugs such as doxorubicin, food dyes, toxins such as mercury, or inherited conditions such as porphyria—and review the
patient's historical and physical examination findings.4 If you suspect pseudohematuria, persistent discoloration of urine supernatant after centrifugation may provide further evidence
of this condition. If you cannot find evidence of an abnormal exogenous or endogenous pigment resulting in discoloration,
it is possible that the color is a normal manifestation of urochrome and urobilin (normal urine pigments) in a concentrated
urine sample. In this instance, the urine typically has a dark-yellow to brown hue.
In rare instances, abnormal pigment in urine cannot be identified by standard evaluation methods and, if persistent, could
be pursued by expanded laboratory testing. State veterinary diagnostic laboratories are good resources for investigating the
possible presence of toxins, dyes, medications, and porphyrins. In addition, PennGen, the Section of Medical Genetics associated
with the University of Pennsylvania School of Veterinary Medicine, may be able to provide guidance in detecting inherited
disorders of heme synthesis in young patients.
STEP 2: RE-EVALUATE HISTORICAL AND PHYSICAL EXAMINATION FINDINGS
A thorough history and physical examination often play important roles in identifying hematuria as a potential problem and
localizing the source of hematuria (Figure 2). Obtain the patient's reproductive history and, in intact females, estrous cycle information as part of a complete history.
Ask the owner about the possibility of trauma to the pet, including whether the pet has a history of recent vigorous exercise
prior to the observation of discolored urine.
Note clinical signs, history, and variations in hematuria based on the collection method
Identifying signs of systemic disease, urination frequency, and dysuria can help establish whether the hematuria more likely
originates from the upper urinary tract, lower urinary tract, or genital tract. Classic signs of lower urinary tract disease
include pollakiuria and dysuria. Signs of systemic disease such as weight loss or fever support upper urinary tract or, in
some cases, genital tract disease.
Difficult defecation in male dogs may indicate prostatic disease. A patient's medication history or its potential exposure
to toxins may signal hematuria related to a coagulopathy or originating from the upper urinary tract. Determining whether
the owner has seen evidence of bleeding unrelated to the urinary tract may also connect hematuria to a coagulopathy. Suspect
a coagulopathy if the physical examination reveals bleeding from another organ system, including petechiation or ecchymoses
of the skin. Perform a fundic examination not only to determine evidence of infectious or neoplastic disease but also to look
for retinal hemorrhage that could indicate a coagulopathy.
Although systemic hypertension is not generally considered a primary cause of hematuria, its presence is often associated
with renal disease and could exacerbate bleeding and alter treatment. Historical and physical findings that may indicate systemic
hypertension include polydipsia and polyuria; cardiac murmur; tachycardia; epistaxis; neurologic signs such as disorientation,
ataxia, or seizures; and ocular abnormalities such as choroidopathy, retinopathy, and hemorrhage.
When blood is observed grossly in a voided sample but is not as readily apparent in urine obtained by cystocentesis or catheterization,
suspect a genital or urethral source of hematuria. However, hematuria from a genital tract or urethral source can sometimes
be observed in both voided and nonvoided samples since the collection technique can result in iatrogenic RBC contamination
or because material from the genital tract or urethra may reflux into the bladder, especially in patients with prostatic disease.