Practical Points in Emergency CT for Emergency Physicians
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Transcript of Practical Points in Emergency CT for Emergency Physicians
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Practical Points in Emergency CT for EP
Rathachai Kaewlai, MDRamathibodi Hospital, Mahidol University, Bangkok
Annual Conference of Thai Emergency Physicians (ACTEP)Greenery Resort Khao Yai, Nakhon Ratchasima | 28 Nov 2014
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Emergency Physician Tasks
• Perform a thorough history and physical• Formulate a reasonable DDx• Order imaging tests based on suspected
diagnosis• Correctly perform the imaging test• Correctly interpret the imaging test• Correctly apply the test result to patient care
David T. Schwartz, MD. NYU
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Outline
• Imaging utilization in ED• Radiation dose from emergency CT• IV contrast issues• PO contrast issue• What CT can diagnose and what it cannot
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CT Imaging Share Increases Significantly in a Decade U.S. Medicare Data
CT18%
XR78%
US3%
MRI0%
NM1%
2002
CT30%
XR65%
US4%
MRI1%
NM0%
2012
Levin DC, et al. J Am Coll Radiol 2014;11:1044-1047.
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CT per 1,000 ED visits Also Increases from 6% to 15%U.S. Medicare Data
Levin DC, et al. J Am Coll Radiol 2014;11:1044-1047.
Bundling of upper/lower abdomen
codes2012: 150 CTs per
1000 ED visits
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% of Visits with CT PerformedUSA (15%) vs. Canada (8%)
Berdahl CT, et al. Ann Emerg Med 2013;62:486-494.
20142012
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Fear of Lawsuits Does Not Drives Unnecessary ED High-cost Imaging
Waxman DA, et al. N Eng J Med 2014;371:1518-1525.
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Minimal Variations Found Amount Emergency Physicians on Imaging Utilization
Wong HJ, et al. Radiology 2013;268:779-789.
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More ED Imaging Utilization in Certain Patients’ and Visit Characteristics
Wong HJ, et al. Radiology 2013;268:779-789.
Advanced ageArrived by ambulance
Higher acuity areaMore secondary
diagnoses
MoreHigh-cost imaging when
ED most busyMore
Low-cost imaging when ED least busy
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Lesson #1
• CT continues to be the main imaging workhorse in ED, following x-ray
• CT utilization increases even in the midst of cost-cutting reform and in States where malpractice has been reformed
• What drives CT use in ED is likely multifactorial and physicians’ characteristics might not be a culprit
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There is no safe dose of radiation.- Edward P Radford, MD
Scholar of the Risks from Radiation
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Mechanism of X-ray InjuryMedscape © Nat Rev Cancer 2009
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Tissue Sensitivity
Most sensitive
Least sensitive
Bone marrow (red), colon, lung, stomach, breast
Gonads Bladder, esophagus, liver, thyroidBone surface, brain, salivary glands, skin
Ref: ICRP 2007
Tissue Sensitivity ~ rate of cell proliferation Inversely ~ to age Inversely ~ to degree of cell
differentiation Higher dose = more damage Young = more damage
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Diagnostic x-ray RiskProcedures Effective Dose
(mSv)Risks
CXR (PA), extremity XR <0.1 Negligible
Abdomen XR, LS spine XR 0.1-1 Extremely low “death from flying 7200 km”
Brain CT, single-phase abdomen CT, single-phase chest CT
1-10 Very low “death from driving 3200 km)
Multiphase CT 10-100 Low
Interventions, repeated CT >100 Moderate
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Avoid Unnecessary CT
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Avoid Unnecessary CT: Import Outside Studies into PACS
In an age in which we can download movies and music from the cloud, it is
inexcusable to subject patients to avoidable cost and radiation exposure when the technology exists to ensure
that images are readily accessible.Zane RD. JWatch Emergency Medicine
Moore HB, et al. J Trauma 2013;74:813-817.
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Lesson #2
• CT radiation dose is a real concern especially in children and young adults who have longer life expectancy
• High-radiation risk procedures: multiphase CT and repeated CT
• Beside technical changes on Radiology side, EP can help by selecting an appropriate imaging for clinical question and avoid duplicated exams whenever possible
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IV Contrast
High osmolarity (1500+)Ionic
Low osmolarity (300-900)Non-ionic
OLD, IONIC, HYPEROSMOLAR AGENTS
NEW, NON-IONIC, LOW OSMOLAR AGENTS
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Benefits of IV contrastVisualization of structures and pathologies, focal pathology in solid organs and necessary for CT angio
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Disadvantages of IV ContrastAnaphylactoid reaction (mostly mild: skin rash)
http://aic-server4.aic.cuhk.edu.hk/web8/Hi%20res/anaphylaxis.jpg
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No True Iodine Allergy
Iodine is a part of our body and important source of metabolism (thyroid hormone).Seafood allergy is because of muscular proteins
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Rate of Contrast ReactionLasser EC, et al. Radiology 1997;203:605-610.
5-15% 0.2-0.7%Fatality ~ 2.1 per 1 million (US FDA)
OLD, IONIC, HYPEROSMOLAR AGENTS
NEW, NON-IONIC, LOW OSMOLAR AGENTS
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Lesson #3
• Newer, non-ionic, low-osmolar contrast is much safer than older ones
• Most reactions are mild, cutaneous• There is no true iodine allergy• What we should ask patients: prior history of
reaction to IV contrast (most substantial), atopy and asthma
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Contrast-induced NephropathyControversies
Definition of CIN | No control group on studies of CINNo risk threshold of renal function test | Problem with sCr vs. eGFR
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Acute Kidney Injury: AKIN Definition
• Any one of these within 48 hours of contrast– Absolute increase of sCr >0.3 mg/dL– % increase of sCr >50% (1.5 fold above
baseline)– Urine output decrease to <0.5 mL/kg/h
for at least 6 hrs
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• Serum creatinine limited by – Influence of gender, muscle mass, nutritional status, age– Can be “normal” until GFR decreases by 50%
• Estimated GFR with Cockcroft-Gault or Modification of Diet in Renal Disease (MDRD)
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Acute Kidney Injury from IV Contrast
Data from cardiac cath overestimates risk of intravenous contrastNewhouse JH, et al. AJR Am J Roentgenol 2008;191:376-382.
Cardiac cath data (arterial injection)
IV (venous) injection
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Acute Kidney Injury from IV Contrast
Newhouse JH, et al. AJR Am J Roentgenol 2008;191:376-382.
Studies with a control group of patients NOT receiving IV contrast>50% of 30,000 patients showed change in sCr
>40% showed change of at least 0.4 mg/dL
https://c2.staticflickr.com/6/5049/5241695367_aa1610e8e1_z.jpg
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Risk Threshold
• No universal agreement on threshold• No agreement on how long from baseline to
use sCr before IV contrast• Ramathibodi protocol
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Lesson #4
• Controversies on IV contrast and renal toxicity persist. Now it is best to follow local standardized protocol
• Best method to reduce risk of CIN is adequate hydration prior and after exposure
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Oral Contrast Controversy
Jakebouma.com
V.S.
BARIUM
ThickerLower risk of aspiration
Not used if suspect perforation
WATER SOLUBLE
Higher aspiration riskBetter choice if suspect perforation
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Oral Contrast: Benefitsbetter delineation of bowel, movement to rectum suggests incomplete obstruction or ileus
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Oral Contrast
• New with MDCT, less need for PO contrast• Dramatic decrease in ED time intervals in
patients receiving NCCT in evaluation of flank pain (312 min for renal stone NCCT vs. 599 min for abd CT with PO contrast
Hunyh LN, et al. Emerg Radiol 2004;10:310-313.
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Even without oral contrast, cancer of the colon and terminal ileum can be appreciated
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Lesson #5
• Avoiding oral contrast can help speed up the process of getting a CT
• This can be helpful in certain group of patients: trauma, acute abdomen (not suspected of perforation or fistula)
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Select the Right Imaging Exam
• Selecting correct imaging modality can affect patient outcome, prevent delay and influence type and onset of Rx
• Acute abdominal imaging options: X-ray, ultrasound, CT
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When CT is Helpful
Perforated appendicitis
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When CT is Helpful
Acute cecal diverticulitis
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When CT is Helpful
C.difficile colitis
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When CT is Helpful
Adhesive small bowel obstruction
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When CT is Helpful
Closed loop small bowel obstruction
Closed loop small bowel obstruction
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When CT is Helpful
Mesenteric arterial occlusion with bowel ischemia
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When CT is Helpful
Perforated acute cholecystitis
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When CT is Helpful
Obstructing right UVJ stone
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Lesson #6: Disorders that can be missed by CT -- Abdomen
• Low-grade SBO• Colonic volvulus• Mesenteric ischemia
(early)• Ischemic bowel
obstruction• Ovarian torsion
• Mild pancreatitis• Traumatic bowel
perforation• Diaphragmatic tear• Mild appendicitis
(occasionally)
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Lesson #6: Disorders that can be missed by CT -- Others
• Small SAH• DAI• Early cerebral contusion• Early ischemic stroke• Small lesions (tumors,
aneurysms)• Posterior fossa
• Subsegmental PE• PE in poorly performed
study• Coronary cause (in non-
coronary CTA)
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Conclusion• CT is the main imaging workhorse in ED, following x-ray. What
drives CT use in ED is likely multifactorial• CT radiation dose concern in people with longer life
expectancy• Newer, non-ionic, low-osmolar contrast is much safer than
older ones• Controversies on IV contrast and renal toxicity persist. Now it
is best to follow local standardized protocol• Oral contrast can be avoided in certain scenarios• Know things that can be diagnosed or missed on CT