1. Renee Rutledge, MS4 Diagnostic Radiology Elective

2.  Renal colic CT first proposed for work-up of flank pain in 1995 (Smith et al), vs intravenous urography which was the gold standard at that time  Since then has been shown to have sensitivity of 97%, specificity of 96%, and accuracy of 97%.  Detects presence, size and location of stones and +/- obstruction  ‘00 Case Western ED study found CT significantly increased emergency department clinician diagnostic confidence

3.  Radiation Dose: Estimated effective dose 8.5mSv  Cost: $1100 at OHSU  Most important, estimated relative rate of recurrence is 35.3% over 10 years...do we expose them to cost/radiation each time they have acute onset flank pain?

4.  U Penn study calculated estimated effective doses for patients from renal colic CTs performed over a 6 year period  5564 studies, 144 studies on pediatric pts (age 2-17 years)  Mean effective dose of 8.5 mSv (vs 0.7 mSv for KUB)  176 pts had 3 or more exams, 19 pts had ≥6 & 1 pt had 18!  Estimated cumulative effective doses from 19.5 to 153.7 mSv.  All patients with multiple examinations had a known history of nephrolithiasis.  Estimated risk of cancer induction from a 10 mSv ionizing radiation dose is 1 in 1000 (1 in 2000 fatal)  Cancer induction rate for 100mSv is 1/100!

5.  Italian study compared renal colic CT vs KUB + US with the following conclusions: Renal colic CT KUB + US -Sens 92.4% -Sens 77.1% -Spec 96.4% -Spec 92.7% -PPV 98% -PPV 95.3% -NPV 86.9% -NPV 68%  Overall accuracy of CT was better (94 vs 83%) but...  No clinically important misdiagnoses  All missed stoned passed spontaneously

6.  Elton et al conducted a study of 203 pts with proven ureteral calculi  The following four-finding prediction rule correctly classified 90% of patients presenting to the ED 1. Acute onset 2. Flank pain 3. Hematuria 4. Positive KUB radiograph

7.  Physical findings in ureterolithiasis  Study of 1333 pts with acute abdominal pain  Microscopic hematuria had a sensitivity of 75%, specificity of 99%, positive Likelihood Ratio of 73.1 & negative LR of 0.3  Loin tenderness had a sensitivity of only 15% but specificity of 99%, +LR 27.7, -LR 0.9  Renal tenderness had a sensitivity of 86%, specificity 76%, +LR 3.6, -LR 0.2

8.  LR of 1 indicates no change in pre & post-test probability, the higher the positive LR & lower the negative LR the greater the “diagnostic weight”

9.  Up to 98% of stones ≤5mm pass spontaneously with supportive care such as hydration & pain control  Urgent urologic consultation warranted in pts with urosepsis, acute renal failure, anuria or intractable pain/nausea/vomiting…all noted w/o CT  Urologic intervention is indicated in pts with a stone ≥10 mm in diameter (visible on KUB) and in patients who fail to pass the stone after a trial of conservative management.  Alternative diagnoses detected with renal colic CT like ovarian pathology, pylonephritis, appendicitis and diverticulitis hopefully have other clinical/laboratory findings to point us in that direction.

10.  In a young patient with a high pretest probability (acute, unilateral flank pain with hematuria)…consider omitting the CT & avoiding the radiation.  In older patients with fever, leukocytosis, normal UA or other confounding factors, scan away!

11.  Smith, RC, AT Rosenfield, KA Choe, KR Essenmacher, M Verga, MG Glickman & RC Lange. "Acute flank pain: comparison of non-contrast- enhanced CT and intravenous urography.." Radiology 194(1995): 789-94.  Abramson, Simeon, N Walders, KE Applegate, RC Gilkeson & MR Robbin. "Impact in the Emergency Department of Unenhanced CT on Diagnostic Confidence and Therapeutic Efficacy in Patients with Suspected Renal Colic." American Journal of Roentgenology 175(2000): 1689-95.  Katz, SI, S Saluja, JA Brink & HP Forman. "Radiation Dose Associated with Unenhanced CT for Suspected Renal Colic: Impact of Repetitive Studies." American Journal of Roentgenology 186(2006): 1120-24.  Catalano, Orlando, A Nunziata, F Altei & A Siani. "Suspected ureteral colic: primary helical CT versus selective helical CT after unenhanced radiography and sonography.." American Journal of Roentgenology 178(2002): 379-387.  Elton, TJ, CS Roth, TH Berquist & MD Silverstein. "A clinical prediction rule for the diagnosis of ureteral calculi in emergency departments.." Journal of General Internal Medicine 8(1993): 57-62.  McGee, Stephen. Evidence Based Physical Diagnosis. 2nd. St Louis: Elsevier, 2007.  Segura, JW, GM Preminger, DG Assimos, SP Dretler, RI Kahn, JE Lingeman & JN Macaluso Jr. "Ureteral Stones Clinical Guidelines Panel summary report on the management of ureteral calculi. The American Urological Association.." The Journal of Urology 158(1997): 1915-21.