Clinical Pearls & Morning Reports
Published July 7, 2021
The most common causes of microhematuria are nonmalignant: glomerulopathies (e.g., IgA nephropathy or thin glomerular basement membrane disease) and inflammatory conditions of the urethra, prostate, and bladder, as well as renal calculi and benign prostatic hypertrophy. Read the NEJM Review Article here.
Q: How is true microhematuria currently defined?
A: True microhematuria is most often defined as more than 2 or 3 red cells per high-power field, and this finding should be confirmed on two or three separate urinalyses. Some experts suggest that if even a single urinalysis is positive, a patient should have follow-up urinalyses for at least a year, so as to avoid missing an intermittent source of microhematuria that could signify a clinically important problem.
Q: In a patient with microscopic hematuria, what finding on microscopic examination suggests an upper urinary tract source of bleeding?
A: The morphologic characteristics of red cells, as well as a review of dipstick results, the formed elements in the urinary sediment, and any other urinary abnormalities detected, may suggest whether upper or lower urinary tract bleeding is more likely. Lower urinary tract hematuria is characterized by normal red cells. If dysmorphic red cells are found, the diagnostic evaluation should first focus on the possibility of a glomerulopathy, particularly if casts, especially red-cell casts, are present.
A: Visible hematuria often has an obvious explanation, which is congruent with the patient’s history, signs, and symptoms (e.g., the passage of a kidney stone, acute hemorrhagic cystitis, or a sickle-cell crisis). However, many other conditions can cause visible hematuria. Thus, the evaluation of gross hematuria should be focused on the basis of the patient’s symptoms and concomitant clinical and laboratory findings. In adults over the age of 40 years (some sources suggest a cutoff age of 35 years), an unexplained episode of visible hematuria may signify bladder or upper urinary tract cancer, and most experts suggest urologic referral along with imaging and cystoscopy to rule out cancer. For many patients, ultrasonography plus cystoscopy suffices. CT urography is recommended by some sources but is more costly than ultrasonography and usually includes the administration of contrast material. The use of magnetic resonance imaging is not generally recommended. It is said that dysuria is present in approximately 80% of patients with bladder cancer and that dysuria doubles the likelihood of finding a bladder cancer.
A: Urinary cytologic analysis has long been recommended as a possible adjunct to cystoscopy and can serve as a way to find evidence of small carcinomas that are overlooked on cystoscopy. In a study by Mishriki et al., in which 2278 patients underwent urinary cytologic analysis, only 2 were determined to have cancer on the basis of the cytologic findings. Cytologic analysis in a study by Hofland et al. showed cancer in 4 of 1000 urine samples, and in 2 of those 4 samples, cancer was detected only on the basis of cytologic findings. Current practice is to limit the use of cytologic analysis to cases of gross hematuria or symptomatic hematuria.