Forget the blood, not the stone! Microhaematuria in acute urolithiasis and the role of early CT scanning.
BACKGROUND
Although urinalysis is simple and inexpensive to perform, the finding of microhaematuria on urinalysis may be unreliable for diagnosing urolithiasis.


OBJECTIVE
To evaluate microhaematuria as a diagnostic marker for urolithiasis compared with low-dose unenhanced multidetector computed tomography (MDCT) as the "gold standard".


METHODS
A level 1 emergency department in a tertiary referral university teaching hospital.


METHODS
Retrospective analysis.


METHODS
A study was undertaken to assess whether the finding of microhaematuria was diagnostic for urolithiasis using a low-dose unenhanced MDCT-based diagnosis as the reference standard by reviewing the records of all patients who presented to the emergency department with colicky flank pain and underwent a CT scan between January 2003 and December 2005.


RESULTS
Urolithiasis was present (as defined by low-dose unenhanced MDCT) in 507/638 patients (79%); 341/638 (53%) were true positive for urolithiasis, 76 (12%) were true negative, 55 (9%) were false positive and 166 (26%) were false negative. Microhaematuria as a test for urolithiasis in patients presenting to the emergency department therefore has a sensitivity, specificity, positive predictive value and negative predictive value of 67%, 58%, 86% and 31%, respectively. 58% of the urinalysis results were negative for haematuria in the subset of patients with significant alternative diagnoses.


CONCLUSIONS
The sensitivity, specificity and negative predictive value of microhaematuria on urinalysis for urolithiasis using unenhanced MDCT as the reference standard were low. This suggests that, when urolithiasis is clinically suspected, unenhanced MDCT is indicated without urinalysis being a prerequisite.
Xafis
K
K
Department of Emergency Medicine, University Hospital of Berne, Berne 3010, Switzerland.
Thalmann
G
G
Benneker
L M
LM
Stoupis
C
C
Buggy
D J
DJ
Zimmermann
H
H
Exadaktylos
A K
AK
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D042241:Early Diagnosis; D004636:Emergency Service, Hospital; D005188:False Negative Reactions; D005189:False Positive Reactions; D006417:Hematuria / Q000209:etiology*; D006801:Humans; D008875:Middle Aged; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016482:Urinalysis / Q000592:standards*; D052878:Urolithiasis / Q000150:complications / Q000175:diagnosis*; D055815:Young Adult