The characteristics of
urate metabolism in renal hypouricemic patients with
hematuria were studied to clarify the risk factors for
hematuria in patients with
renal hypouricemia. In 16 Japanese patients with isolated
renal hypouricemia,
urate metabolism was measured using the
urate clearance study and the subtype of
renal hypouricemia [defective presecretory reabsorption (Pre), defective postsecretory reabsorption (Post), enhanced tubular secretion (Secretion) and defective presecretory and postsecretory reabsorption (Pre&Post)] were determined by the pharmacological tests.
Hematuria was seen in 7 out of the 16 patients (44%), all of whom were females (58%). Serum
urate and urinary
urate concentrations were significantly higher in the group with
hematuria (Sur = 1.76 +/- 0.31 mg/dl and Uur/Ucr = 0.75 +/- 0.12: p<0.05) than in the group without
hematuria (Sur = 1.44 +/- 0.46 mg/dl and Uur/Ucr = 0.56 +/- 0.04), although there was no difference in the
urate excretion rate between the two groups.
Hematuria was more likely to be accompanied by Post (75%) and Secretion (75%), which showed significantly higher urinary
urate concentration (Uur/Ucr = 0.75 +/- 0.1 and 0.69 +/- 0.13, respectively) than by Pre (25%) and Pre&Post (0%), which showed lower urinary
urate concentration (0.61 +/- 0.06 and 0.62 +/- 0.05, respectively). The risk factors for
hematuria in patients with
renal hypouricemia are the elevation of urinary
urate concentration and the subtypes of Post and Secretion.