The diagnostic approach to hematuria - Veterinary Medicine
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The diagnostic approach to hematuria
A common finding in dogs and cats, hematuria causes a swarm of differential diagnoses to come to mind. This internist provides a series of algorithms to help you zero in on the cause.


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.


Figure 2
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.

Figure 3
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.


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