Renee Rutledge, MS4
Diagnostic Radiology Elective
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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?
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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 -217
years)
Mean effective dose of 8.5mSv (vs 0.7 mSv for KUB)
176 pts had 3 ormore exams, 19 pts had ≥6 & 1 pt had
18!
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Estimated cumulative effective doses from 19.5 to 153.7mSv.
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!
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Italian study compared renal colic CT vs KUB + US
with the following conclusions:
Renal colic CT
KUB + US
-Sens92.4%
-Sens77.1%
-Spec 96.4%
-Spec 92.7%
-PPV 98%
-PPV 95.3%
-NPV 86.9%
-NPV 68%
Overall accuracy of CT was better (94vs 83%) but...
No clinically important misdiagnoses
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All missed stoned passed spontaneously
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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.
2.
3.
4.
Acute onset
Flank pain
Hematuria
Positive KUB radiograph
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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
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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”
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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.
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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!
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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.