Practical considerations for the further investigation of isolated asymptomatic microhematuria

The finding of isolated asymptomatic microhematuria usually raises questions about the need to perform further invasive investigations. Phase contrast microscopy of the urine sediment is a sensitive, non invasive method that provides information on the glomerular or non glomerular origin of hematuria, as well as on its grade. This analysis, however, must be performed by an experienced technician under standard conditions. The presence of dysmorphic (i.e. glomerular) erythrocytes indicates a glomerular disease if the count is higher than 10 erythrocytes per microliter and is considered physiological if the count is below this number. In these two cases, no further investigation will be undertaken if all criteria for isolated microhematuria are verified. Conversely, isomorphic erythrocytes reveal a non glomerular origin of hematuria, which may indicate a serious urological disease. In this case, further investigations (e.g. ultrasound, urine cytology) are recommended, taking into account the age of the patient.