Is there a learning curve in diagnosing urolithiasis with noncontrast helical computed tomography?
OBJECTIVE
To report one department's experience with helical computed tomographic (HCT) evaluation of patients with suspected renal colic to diagnose ureteral calculi; to determine whether there is a learning curve in performing HCT in this context; and to determine whether HCT for the evaluation of renal colic exposes patients to more radiation than the standard intravenous pyelography (IVP) combined with nephrotomography.


METHODS
All patients presenting to the emergency department with flank or abdominal pain were evaluated with nonreformatted noncontrast HCT. To determine changes in diagnostic accuracy, patients were divided into 2 groups: those evaluated between September 1996 and January 1997 (group 1, 67 patients), and those seen from February to June 1997 (group 2, 53 patients). A radiation exposure study was performed using phantoms, and radiation exposure for HCT, IVP and nephrotomography was measured.


RESULTS
Review of HCT scans to diagnose ureteral calculi had a sensitivity of 91.7%, specificity of 82.6%, and accuracy of 87.2% in group 1, and a sensitivity of 95.5%, specificity of 86.7%, and accuracy of 91.9% in group 2. Patients undergoing IVP with nephrotomography were exposed to an effective dose equivalent of 343 mrem (dSv) (for men) and 664 mrem (for women). The effective dose equivalent for an HCT scan was 180 mrem.


CONCLUSIONS
HCT offers excellent, rapid diagnostic accuracy without the need for intravenous contrast medium and with a lower radiation exposure level than IVP in evaluating patients with acute flank pain. There is a small but real learning curve in evaluating patients with acute flank pain with HCT.
Department of Urology, Wake Forest University, School of Medicine, Winston-Salem, NC 27157, USA. crosser@wfubmc.edu
C J
CJ
Rosser
R
R
Zagoria
R
R
Dixon
W C
WC
Scurry
R L
RL
Bare
D L
DL
McCullough
D G
DG
Assimos
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002983:Clinical Competence; D003085:Colic / Q000000981:diagnostic imaging; D003287:Contrast Media; D005260:Female; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed; D014513:Ureter / Q000000981:diagnostic imaging; D014514:Ureteral Calculi / Q000000981:diagnostic imaging*; D014567:Urography
D003287:Contrast Media