The presence of microscopic hematuria detected by urine dipstick test in the evaluation of patients with renal colic

Abstract

Urolithiasis is a common diagnosis in patients presenting at our hospital with flank pain. One of the most important steps in the diagnostic algorithm of renal colic is the presence of hematuria, but this fact has been challenged by authors reporting a negative urinalysis for microscopic hematuria in about 9-18% of such patients. Our aim was to investigate whether the same results are obtained when a sample of urine is tested with a urine dipstick test (UDT) at the time of the initial examination. Data from patients with the clinical diagnosis of renal colic examined at the emergency department of our hospital were reviewed, and the sensitivity of hematuria in urine samples tested by UDT was recorded in a group consisting of patients for whom imaging showed evidence of a stone >3 mm in size. In cases in which UDT was negative, or showed only traces of red blood cells (RBCs), a formal urinalysis was performed. A total of 609 patients were finally included in the study, with a mean age of 49.2 years. Average stone size was 5.8 mm, located mainly in the lower part of the ureter. Dipstick analysis was positive for hematuria in 92.9%. A urinalysis, with a cut-off point of less than three red blood cells per high power field, was used as a means to verify the results of the UDT in 17.8% of cases: in 7.1% of UDT negative patients and 10.7% of patients with traces of blood. The urinalysis was negative in 5.1% of patients, adding only 2% to the diagnostic accuracy of UDT. Therefore, our findings suggest that the sensitivity of a UDT for hematuria in cases of suspected renal colic has a high degree of accuracy when performed at the emergency department, and can be used as a first-line, low cost examination. A microscopic analysis may be useful when the UDT is negative or not clear enough, to verify the results.