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

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

Outline

• Imaging utilization in ED

• Radiation dose from emergency CT

• IV contrast issues

• PO contrast issue

• What CT can diagnose and what it cannot

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.

CT per 1,000 ED visits Also Increases from 6% to 15%

U.S. Medicare DataLevin DC, et al. J Am Coll Radiol 2014;11:1044-1047.

Bundling of upper/lower abdomen

codes

2012: 150 CTs per 1000 ED visits

% of Visits with CT PerformedUSA (15%) vs. Canada (8%)

Berdahl CT, et al. Ann Emerg Med 2013;62:486-494.

20142012

Fear of Lawsuits Does Not Drives Unnecessary ED High-cost Imaging

Waxman DA, et al. N Eng J Med 2014;371:1518-1525.

Minimal Variations Found Amount Emergency Physicians on Imaging

UtilizationWong HJ, et al. Radiology 2013;268:779-789.

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

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 multifactorialand physicians’ characteristics might not be a culprit

There is no safe dose of radiation.- Edward P Radford, MD

Scholar of the Risks from Radiation

Mechanism of X-ray InjuryMedscape © Nat Rev Cancer 2009

Tissue Sensitivity

Most sensitive

Least sensitive

Bone marrow (red), colon, lung, stomach, breast

Gonads

Bladder, esophagus, liver, thyroid

Bone 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

Diagnostic x-ray Risk

Procedures 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-phaseabdomen CT, single-phase chest CT

1-10 Very low “death from driving 3200 km)

Multiphase CT 10-100 Low

Interventions, repeated CT >100 Moderate

Avoid Unnecessary CT

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.

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

IV Contrast

High osmolarity (1500+)Ionic

Low osmolarity (300-900)Non-ionic

OLD, IONIC, HYPEROSMOLAR AGENTS

NEW, NON-IONIC, LOW OSMOLAR AGENTS

Benefits of IV contrastVisualization of structures and pathologies, focal pathology in solid organs and necessary for CT angio

Disadvantages of IV ContrastAnaphylactoid reaction (mostly mild: skin rash)

http://aic-server4.aic.cuhk.edu.hk/web8/Hi%20res/anaphylaxis.jpg

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

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

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

Contrast-induced NephropathyControversies

Definition of CIN | No control group on studies of CINNo risk threshold of renal function test | Problem with sCr vs. eGFR

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/hfor at least 6 hrs

• 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)

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

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

Risk Threshold

• No universal agreement on threshold

• No agreement on how long from baseline to use sCr before IV contrast

• Ramathibodi protocol

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

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

Oral Contrast: Benefitsbetter delineation of bowel, movement to rectum suggests incomplete obstruction or ileus

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.

Even without oral contrast, cancer of the colon and terminal ileum can be appreciated

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)

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

When CT is Helpful

Perforated appendicitis

When CT is Helpful

Acute cecal diverticulitis

When CT is Helpful

C.difficile colitis

When CT is Helpful

Adhesive small bowel obstruction

When CT is Helpful

Closed loop small bowel obstruction

Closed loop small bowel obstruction

When CT is Helpful

Mesenteric arterial occlusion with bowel ischemia

When CT is Helpful

Perforated acute cholecystitis

When CT is Helpful

Obstructing right UVJ stone

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)

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)

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