UTILITY OF RENAL COLIC CT IN ACUTE

FLANK PAIN

Renee Rutledge, MS4Diagnostic Radiology Elective

The New Gold Standard for Detecting Ureteral Calculi…

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

Disadvantages

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?

Radiation Dose

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!

Other diagnostic imaging options

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

Clinical Predictors

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 onset2. Flank pain3. Hematuria4. Positive KUB radiograph

Evidence Based Physical Diagnosis by Stephen McGee

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

Is a +LR of 73 significant?

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”

Does the exact size/location of stone change treatment?

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.

Your call, but my humble suggestion is…

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!

Sources 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.