Significance of isolated hematuria and isolated pyuria in systemic lupus erythematosus

Hematuria or sterile pyuria as isolated urinary findings present a clinical dilemma for the treating physician. Our objective was to determine whether isolated hematuria and isolated sterile pyuria are associated with active systemic lupus erythematosus (SLE) with respect to renal and non-renal dise ase activity. This is a descriptive study from a large SLE cohort followed prospectively at the University of Toronto Lupus Clinic. All episodes of isolated hematur ia and isolated pyuria between 1970 and 2000 were identified from our datab ase. Isolated hematuria was defined as >5 red blood cells per high power fi eld: isolated sterile pyuria was defined as >5 white blood cells per high p ower field in the absence of urinary infection and other renal manifestatio ns. Non-renal disease activity (defined as nrSLEDAI > I) was determined at first episode of isolated hematuria and pyuria. Renal disease activity was assessed by scoring renal biopsies within 3 months of detecting isolated he maturia or sterile pyuria. Thirty-four percent (323/946) of our cohort had at least one episode of iso lated hematuria. Seventy-seven percent of these patients had concurrent non -renal disease activity. Of the 22 biopsies scored with isolated hematuria, 96% were abnormal (WHO > class I), including 52% with active nephritis. Tw enty-three percent (215/946) had at least one episode of isolated sterile p yuria. Seventy-eight percent of these patients had concurrent non-renal dis ease activity. All 12 biopsies scored with isolated pyuria were abnormal(WH O Class >1). including 75% with active nephritis. The appearance of isolate d hematuria and isolated pyuria is associated with active renal and nonrena l disease activity. An ongoing debate has emerged regarding the significance of isolated hematu ria and isolated pyuria with respect to SLE disease activity. The results o f this study suggest that isolated hematuria and isolated pyuria is associa ted with active renal and non-renal disease activity. Thus isolated hematur ia and isolated sterile pyuria should be considered manifestations of activ e SLE.