[Microhematuria of renal origin--differential diagnosis, clarification and interpretation].

Microhematuria offers a wide spectrum of diagnostic possibilities. Once the finding is confirmed, the diagnosis of prerenal, renal-parenchymatous and postrenal (or even factitious) hematuria and differentiation between glomerular and nonglomerular bleeding sources is based on the patient's history, a complete clinical status, special urinary findings (mainly red cell casts, proteinuria and red cell morphology) and blood chemistry (serum creatinine or creatinine clearance). If on the basis of this information glomerular or renal-parenchymatous microhematuria seems likely, further diagnostic procedures include immunological tests and, if indicated and justified, renal biopsy. Urography and other imaging procedures, urinary cytology and cystoscopy (firmly indicated when doubts persist or all the evidence points to postrenal hematuria) are deferred whenever glomerular hematuria seems likely. The special aspects of isolated renal microhematuria are discussed.