Kim TH, et al. - Factors associated with absent hematuria were investigated in patients with symptomatic urinary stones. In this large cohort of 798 patients with renal colic, 6% had no microhematuria. In multivariate analysis, perinephric stranding, a lower stone location (located in an area from the distal ureter to the bladder), and elevated serum blood urea nitrogen (BUN) levels were associated with absent hematuria, however, no difference in the demographics, time of presentation and degree and location of pain between the groups (with and without hematuria) was noted.