[Asymptomatic microhematuria: follow-up in 39 patients].

: We have studied 39 patients with asymptomatic microhematuria (AM) over a mean period of 3.7 years (2.6 to 5.3). In 28 patients, the etiology of the AM had remained unknown despite extensive work-up at the time of AM diagnosis. During follow-up, the urine was examined by the dipstick method and a urine sediment was prepared by standard techniques. Erythrocyturia was judged as grade I or grade II (3-9 or less than 9 erythrocytes/hpf) and classified by phase-contrast microscopy as glomerular or non-glomerular (greater than 30% or less than 30% of erythrocytes with glomerular characteristics). The results were as follows. All patients were in good health during the whole follow-up. None developed significant proteinuria or gross hematuria. AM persisted in 28 of the 39 patients (72%) and in 22 of the 28 with AM of unknown etiology (79%). Persistence of AM was independent of grade and morphology of AM. Among the patients with AM of unknown cause, the fifteen who initially showed grade I AM had grade I AM in 92% and grade II AM in 8% of follow-up urinalyses, and the seven with grade II AM at the first examination had grade II AM in 65% and grade I AM in 35% of follow-up urinalyses (p = 0.007). The last morphologic classification of AM corresponded to the first in all patients with grade II AM, but only in 74% of patients with grade I AM. The following conclusions were drawn. (1) Most AM of unknown etiology persists over several years irrespective of grade and morphology of erythrocyturia.(ABSTRACT TRUNCATED AT 250 WORDS)