A previously healthy 18-year-old woman is seen in your office complaining of a 3-day episode of "red urine," which has now resolved. She is frightened because this has never happened to her before.
- What additional symptoms should the historian ask about in a patient with this complaint?
- Can you make a diagnosis based on history alone?
- Should the patient have urgent radiographic imaging of her urinary tract?
Few symptoms are more alarming to patients than grossly red or brown urine. The first priority is to determine whether the discoloration is due to blood in the urine or another cause. Unless the symptoms are strongly suggestive, the diagnosis of gross hematuria, or visible blood in the urine, must be confirmed by centrifuging the urine specimen (Figure 41–1).
Diagnostic approach: Patient with suspected gross hematuria.
Microscopic hematuria is usually not noticed by the patient, but rather diagnosed on urinalysis performed after treatment for urinary tract infection or on routine urinalysis during insurance or employment screening. Neither the US Preventive Health Services Task Force nor the Canadian Task Force on Periodic Health recommends routine screening for microscopic hematuria.1
The presence of microscopic hematuria has a low predictive value for bladder cancer, even in high-risk elderly patients, and there is currently no evidence that early detection improves prognosis.1,2 In 5 studies examining prevalence, the percentage of patients with asymptomatic microscopic hematuria varied from 0.19% to 16.1%.3 Some studies indicate the prevalence is higher in older people and higher among women than men.1
For purposes of the ensuing discussion, it is assumed that the diagnosis of true gross or microscopic hematuria has already been established. Although the prevalence of serious disease (eg, malignancy) is higher in patients with gross hematuria, microscopic hematuria may also indicate significant genitourinary pathology.4,5 A careful history is essential in the evaluation of the patient with either condition.
|Hematuria||Bleeding from the urinary tract.|
|Gross hematuria||The presence of blood in the urine in sufficient quantity to be visible to the naked eye. A recent study indicates that more than 95% of clinicians will only recognize gross hematuria when > 3500 red blood cells per high-power field are present.6|
|Microscopic hematuria||2–3 red blood cells per high-power field on urine microscopy. A lower cutoff results in more false-positive results (decreased specificity), whereas a higher cutoff results in more missed disease (decreased sensitivity).|
Both microscopic and gross hematuria can be manifestations of serious disease, including malignancy.
|Common Causes of Microscopic and Gross Hematuria4|
|Hematuria, No. (%) of Patientsa|
|Microscopic (n = 1689)||Gross (n = 1200)|