How many RBCs per high-power field in a routine urinalysis are notable and warrant further investigation?
Periodic review of a subject frequently taken for granted, eg, microhematuria, is not only appropriate but essential. With improvement of techniques and better understanding of various disease processes, it is important to update the clinical implications of microhematuria.
Carson et al (p 149) indicate that 81% of their patients with microhematuria followed up for two years had substantial genitourinary pathological conditions. Approximately 20 years ago, one of the authors, Laurence F. Green, MD, recorded only 10% of patients with microhematuria who had a substantive pathological condition. Thirteen percent of the present group of patients who were followed up for the two years had a malignant neoplasm of the genitourinary tract. The same evaluation 20 years ago showed only 2.2% of patients with microhematuria to have a malignant neoplasm of the urinary tract. The authors