title: Impact of date of onset on the absence of hematuria in patients with acute renal colic.
abstract: OBJECTIVE
  Hematuria is absent in a significant proportion of patients with acute ureterolithiasis. We determined whether time from pain onset has any impact on the sensitivity of hematuria tests in the diagnosis of ureterolithiasis.
  
  
  METHODS
  We retrospectively reviewed the records of 537 patients with suspected acute unilateral renal colic during a 29-month period with regard to the interval between pain onset and urinalysis, including the dipstick test and microscopic red blood cell count as well as other clinical findings. Although ureterolithiasis was determined by plain x-ray and ultrasonography primarily, stone absence was diagnosed by computerized tomography.
  
  
  RESULTS
  Ureterolithiasis was diagnosed in 452 patients (84.2%). The dipstick test had higher sensitivity (0.780 vs 0.718) but it was equivalent on ROC analysis compared with microscopic examination (area under the curve 0.696 vs 0.694, p = 0.92). Hematuria test sensitivity was 0.95, 0.83, 0.65, 0.68, 0.77, 0.86 and 0.68 on days 0, 1, 2, 3, 4, 5 to 7 and 8 or more from pain onset, respectively (ANOVA p = 0.004). On logistic regression analysis including hydronephrosis grade, and stone size and location the interval between onset and urinalysis was the only independent factor affecting the incidence of negative hematuria in patients with ureterolithiasis (p = 0.03, 95% CI 0.89 to 0.99).
  
  
  CONCLUSIONS
  The interval between pain onset and urine collection has a significant impact on the diagnostic performance of hematuria tests. The incidence of negative hematuria is highest on the days 3 and 4.
mesh_terms: D000208:Acute Disease; D000328:Adult; D003085:Colic / Q000150:complications*; D005260:Female; D006417:Hematuria / Q000209:etiology*; D006801:Humans; D007674:Kidney Diseases / Q000150:complications*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013997:Time Factors