Is hematuria really hematuria?
Asymptomatic Microscopic Hematuria (AMH)
A perplexing urologic problem that I frequently hear Primary Care Physicians ask about is microscopic hematuria. I have decided to devote a PCP Update to this topic acknowledging that the vast majority of the following information was taken right from the American Urologic Association Guidelines for the diagnosis, evaluation, and follow-up of asymptomatic microscopic hematuria in adults.
A separate article will discuss gross (visible) hematuria which does require urologic evaluation unless secondary to a documented urinary tract infection by culture.
The definition of asymptomatic microscopic hematuria is defined as three or more red blood cells (RBC) per high-powered field on a properly collected urine specimen. A negative repeat microscopic urinalysis following a positive test does not preclude the need for evaluation as outlined below. A positive dipstick urinalysis does not define asymptomatic microscopic hematuria (AMH).
Evaluation should be based solely on the findings of a microscopic evaluation of the urinary sediment and not on a dipstick. Realizing that most primary care practices do not routinely do microscopic examinations, the first step at a urologic office is to obtain a urine specimen in addition to a dipstick and do a microscopic examination. If, indeed, the dipstick is positive, but the microscopic examination is negative, patients are given three dipsticks to take home and check at various times on different days and then return for a second microscopic evaluation. Again, three or more red blood cells per high-powered field are required to confirm the diagnosis of AMH. In the absence of AMH, and there is some concern on the part of the referring physician, patient or urologist, then a renal ultrasound can be obtained.
Assessment of AMH should include a careful history, exam, and laboratory evaluation to rule out benign causes of AMH such as infection, menstruation, vigorous exercise, medical renal disease, trauma, or recent urologic procedures.
Once a benign cause has been ruled out, the present of AMH should prompt a urologic evaluation. In the initial evaluation, an estimate of renal function should be obtained (may include calculated eGFR, creatinine, and BUN). AMH that occurs in patients who are taking anti-coagulants requires urologic evaluation and nephologic evaluation regardless of the type and level of anti-coagulant therapy. For the urologic evaluation of AMH, cystoscopy should be performed in all patients over the age of 35.
In patients younger than 35, cystoscopy may be performed at the physician's discretion. Cystoscopy should be performed in all patients who present with risk factors for urinary malignancy (irritative voiding symptoms, current or past tobacco use, chemical exposures) regardless of age.
The initial evaluation of AMH should include radiographic evaluation. Multi-phasic computed tomographic (CT) urography with and without IV contrast, including secretory phase to evaluate the renal parenchyma to rule out a renal mass and an excretory phase to evaluate the urothelium of the upper tract. CT is the imaging procedure of choice because it has the highest sensitivity and specificity for imaging the upper tracts. In patients with relative or absolute contraindications that preclude the use of multi-phasic CT (renal insufficiency, pregnancy, contrast allergy), MRI with and without IV contrast is an acceptable alternative. The use of urine cytology and urine markers are not recommended as part of the routine evaluation of AMH. In patients with persistent AMH in spite of a negative workup, or those with other risk factors for carcinoma in situ (irritative symptoms, current or past tobacco use, chemical exposure) cytology may be useful.
The bottom line recommendations for primary care physicians is that if the dipstick shows any evidence of blood, microscopic examination should be performed. If you are unable to do so, we would be happy to see the patients in our office. Once microscopic evaluation of the urine can be obtained, a decision can be made whether to proceed with a work-up and exactly what type of work-up is indicated. The lack of symptoms associated with AMH is not indicative of the absence of problems since rarely will upper tract pathology result in symptoms. While lower tract irritative symptoms can be associated with bladder cancer, the absence of these symptoms does not exclude the possibility of significant disease.
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