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.


VETERINARY MEDICINE


Urinalysis

Urinalysis is an essential part of evaluating hematuria, regardless of the source. Always consider the method of urine collection and the urine specific gravity when evaluating urinalysis results. Urinalysis is best performed within 30 minutes of sample collection. A longer delay can result in cellular deterioration, pH changes, bacterial growth, and precipitates that can be confused with crystals.5 Refrigerate urine samples that cannot be examined within 30 minutes of collection, but gradually warm them to room temperature to obtain accurate dipstick chemical analysis.

In most cases, obtaining urine by cystocentesis is desirable to avoid genital and environmental contamination. When a coagulopathy is suspected, cystocentesis should only be cautiously attempted because of the possibility of causing excessive bleeding. When hematuria is suspected to be of genital or urethral origin, comparing urinalysis results from a voided sample with results from a cystocentesis sample may provide evidence of a genital or urethral source.

Urine chemical and sediment examination. Urine chemical and sediment findings such as protein, infectious organisms, white blood cells, casts, and crystals can help determine definitive or contributing causes of hematuria. Always assess the clinical relevance of these findings in relationship to the urine collection technique and the total clinical evaluation of the patient. For example, crystals can be a normal finding in urine samples and are not considered a cause of hematuria, although their presence may be associated with potential sources of hematuria such as uroliths.

If you suspect a lower urinary tract infection (UTI), it is reasonable to try to eradicate the infection in an attempt to resolve the hematuria. Ideally, treat bacterial infections by selecting antibiotics based on bacterial culture and antimicrobial sensitivity testing results. Treat patients with multiple episodes of UTIs, systemic signs of illness, systemic fungal infections, genital tract infections, or upper UTIs with longer courses of antimicrobial drugs. These patients should undergo further diagnostic procedures to identify complicating factors and other organ system involvement. If parasites are identified in urine, such as Capillaria or Dioctophyma species ova or Dirofilaria species microfilariae, administer an appropriate parasiticide. In patients with Dioctophyma or Dirofilaria species infections, perform additional diagnostic procedures before treatment to assess kidney function and structure as well as other organs that might be affected by these parasites.

Blood pressure measurement

Routine screening for systemic hypertension by performing blood pressure measurements is advisable if you suspect upper urinary tract disorders or in cases in which localizing the source of hematuria cannot be reasonably accomplished through historical and physical examination findings.

Coagulation profile


Figure 6
Coagulopathy-related hematuria is more likely to be caused by a primary hemostatic defect involving platelets rather than secondary hemostatic clotting factor defects. Consequently, consider evaluating von Willebrand's factor activity and platelet function if the initial coagulation profile (Figure 6) is unremarkable or inconclusive. When a coagulopathy is identified, it is advisable to find the location of bleeding from the urogenital tract and to rule out any concurrent urogenital disease that might be exacerbating the patient's bleeding tendencies.

Diagnostic imaging

Diagnostic imaging plays an important role in tracking down the site and cause of hematuria. Abdominal radiography and ultrasonography are usually indicated in cases of hematuria. Imaging is indicated early in the diagnostic process in patients with a recent history of trauma or physical examination findings such as abdominal masses or abnormalities associated with a kidney, the bladder, the uterus, or the prostate. Use imaging to thoroughly examine the urogenital tract for irregularities, including masses, abnormalities in the shape and size of structures, and uroliths or bladder sediment.

Although blind aspirates and biopsies of suspicious areas of the urogenital tract can be performed, ultrasonography provides a potentially safer, more accurate method of obtaining samples for cytologic or histologic examination or culture. In patients with lower urinary tract signs, a retrograde contrast study may be indicated to identify urethral abnormalities, further evaluate bladder masses, and recognize radiolucent calculi. Patients with evidence of upper urinary tract disease or hematuria that has yet to be localized may be candidates for an excretory urogram to identify functional or subtler structural abnormalities. To avoid introducing bacteria or other contaminants, collect samples from the urogenital tract for bacterial culture or other analysis before performing contrast procedures. Advanced imaging such as computed tomography or magnetic resonance imaging may be indicated when the results of traditional imaging methods are inconclusive.


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Source: VETERINARY MEDICINE,
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