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Abdominal CT: Necessity, Nephropathy, and Allergy Myths. Joe Lex, MD, FACEP, FAAEM Temple University School of Medicine Philadelphia, PA [email protected] Disclosure. Nothing to declare. Cape Town, SA. www.GiantSteps-EM.Com. July 19 – 22 nd San Diego, California

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abdominal ct necessity nephropathy and allergy myths

Abdominal CT: Necessity, Nephropathy, and Allergy Myths

Joe Lex, MD, FACEP, FAAEM

Temple University School of Medicine

Philadelphia, PA

[email protected]

disclosure
Disclosure

Nothing

to

declare

slide4

www.GiantSteps-EM.Com

July 19 – 22nd

San Diego, California

Four Speakers Only:

Amal Mattu

Ghazala Sharieff

Joe Lex

Greg Henry

Not a speaker

slide5

Mediterranean Emergency Medicine Congress V

14-17 September 2009

Valencia, Spain

objectives
Objectives
  • Assess the necessity of oral and intravenous contrast material
  • Discuss strategies to avoid adverse outcomes from intravenous contrast
question 1
Question #1

How does oral contrast affect the accuracy of an abdominal CT scan?

history of contrast
History of Contrast
  • “Step and Scan” replaced by helical technology
  • Single-beam replaced by multiple beam
  • Rapid scans eliminate artifact from movement, respirations, peristalsis
importance of contrast
Importance of Contrast
  • Many studies show no contrast required in most situations
  • Confounding variables:
    • Scanner: dynamic vs. helical vs. multi-detector
    • Contrast: oral vs. IV vs. rectal
    • Interpreter reliability
oral contrast longer stay
Oral Contrast = Longer Stay
  • High volume urban ED: 107,000 visits / year
  • N = 183 patients
  • Excluded trauma, pediatrics, pregnant

Huynh LN, et al. Emerg Radiol. 2004 Jul; 10(6):310-3.

oral contrast longer stay1
Oral Contrast = Longer Stay

Huynh LN, et al. Emerg Radiol. 2004 Jul; 10(6):310-3.

oral contrast accuracy
Oral Contrast: Accuracy
  • 118 patients scanned before and after oral contrast
  • Blinded interpretation by different radiologists

Lee SY, et al. Emerg Radiol. 2006 May; 12(4):150-7.

oral contrast accuracy1
Oral Contrast: Accuracy
  • 11 had normal non-contrast but abnormal contrast
  • 6 had abnormal non-contrast but normal contrast scans
  • 4 had both scans abnormal, but disagreement over abnormality

Lee SY, et al. Emerg Radiol. 2006 May; 12(4):150-7.

oral contrast accuracy2
Oral Contrast: Accuracy
  • Post-hoc analysis: one true discordant result
  • Unblinded review: disagreement due to inter-observer variability
  • Other studies: discrepancy rates up to 38%

Lee SY, et al. Emerg Radiol. 2006 May; 12(4):150-7.

oral contrast appendicitis
Oral Contrast: Appendicitis
  • Meta-analysis: 23 studies of CT for appendicitis
  • CT without contrast similar to or better than CT with contrast

Anderson BA, et al. Am J Surg. 2005 Sep; 190(3):474-8.

oral contrast appendicitis1
Oral Contrast: Appendicitis

Anderson BA, et al. Am J Surg. 2005 Sep; 190(3):474-8.

oral contrast conclusion
Oral Contrast: Conclusion
  • Many radiologists very comfortable interpreting studies without oral contrast
  • Although oral contrast takes 90 minutes to opacify bowel, it adds 3 hours to ED stay
oral contrast conclusion1
Oral Contrast: Conclusion
  • Oral contrast adds little to accuracy
  • Local radiologist may not be comfortable interpreting studies without oral contrast
question 2
Question #2

How does intravenous contrast affect the accuracy of an abdominal CT scan?

iv contrast risks
IV Contrast: Risks
  • Associated risks
    • Allergic and anaphylactoid reactions
    • Contrast induced nephropathy
  • New scanners adequate to diagnose common problems without IV contrast: appendicitis, diverticulitis, pancreatitis
iv contrast accuracy
IV Contrast: Accuracy
  • 164 unenhanced CT of patients with abdominal pain
  • Diagnosis made in 71 (43%)
  • Non-diagnostic given IV contrast
  • All reviewed by 2 radiologists
  • No significant difference with IV contrast

Basak S, et al. Clin Imaging. 2002 Nov-Dec; 26(6):405-7.

iv contrast necessity
IV Contrast: Necessity
  • Suspected appendicitis: unenhanced CT  laparoscopy
  • Appendicitis diagnosed…

…by CT in 83/103 (80.6%)

…at laparoscopy in 87/103 (84.5%)

  • CT sensitivity 95.4%, specificity 100%

in\'t Hof KH, et al. Br J Surg. 2004 Dec; 91(12):1641-5.

iv contrast necessity1
IV Contrast: Necessity
  • Unenhanced CT in 109 patients
  • Final diagnosis by surgery or F/U
  • 66 TN, 37 TP, 4 FN, 2 FP
    • Sensitivity: 90%, Specificity: 97%
    • PPV and NPV: 95%
    • Accuracy: 94%
  • Alternate diagnosis on CT: 22%

Lane MJ, et al. AJR Am J Roentgenol. 1997 Feb; 168(2):405-9.

conclusions iv contrast
Conclusions: IV contrast
  • CT technology has evolved rapidly
  • IV contrast adds little to accuracy
  • Local radiologists may not be comfortable interpreting studies without IV contrast
adverse reaction occurrence
Adverse Reaction Occurrence
  • 112,000 patients
  • Total reactions: 5.65 %

Shehadi WH. Am J Roentgenol Radium Ther Nucl Med. 1975 May;124(1):145-52

question 3
Question #3

What is the connection between iodine and seafood or shellfish allergy and intravenous contrast material?

iodine allergy
“Iodine Allergy”
  • Physiologic impossibility
  • Iodine essential to life
  • Found in thyroid hormones, amino acids
  • Shellfish allergy to muscle protein tropomyosin

Huang SW. Allergy Asthma Proc. 2005 Nov-Dec;26(6):468-9.

seafood allergy
Seafood Allergy
  • Anaphylactoid, not IgE mediated
  • No response to skin testing
  • Recurrence: <25% repeat
  • Increased risk: foods, asthma, hay-fever, hives, drug allergies
  • No additional risk for seafood

Schlifke A, et al. Can J Emerg Med. 2003; 5(3):166-168.

question 4
Question #4

If a patient says “I’m allergic to contrast dye,” can’t I just give some diphenhydramine and steroids before they’re injected?

preventing adverse reactions
Preventing Adverse Reactions
  • ACR recommendation if history of moderate or severe reaction

50 mg prednisone 13, 7 & 1 hour prior

50 mg diphenhydramine 1 hour prior

32 mg methylprednisolone 12 & 2 hours prior

How does that help us??

http://www.acr.org/s_acr/bin.asp?TrackID=&SID=1&DID=24981&CID=2131&VID=2&DOC=File.PDF

does pretreatment work
Does Pretreatment Work?
  • Meta-analysis: six studies
  • Four used antihistamines
    • Pooled RR: 0.4 (95% CI 0.18–0.9)
  • Insufficient data for pooled statistic for corticosteroids
    • Suggested reduction for methylprednisolone

Delaney A, et al. BMC Med Imaging. 2006 Apr 27;6:2.

does pretreatment work1
Does Pretreatment Work?
  • Steroid pretreatment reduced…

…respiratory symptoms from 1.4% to 0.4%

…respiratory and hemodynamic symptoms from 0.9% to 0.2%

  • NNT to prevent one severe reaction: 100 – 150

Tramer MR, et al. BMJ. 2006 Sep 30; 333(7570):675.

conclusions
Conclusions

Pretreatment…

…in unselected patients not useful

…recommended in patients with prior anaphylaxis

…may not prevent severe or life threatening reactions

Life threatening reactions rare

question 5
Question #5

What about the patient with a history of asthma? Does that increase the risk of an allergic reaction?

asthmatics and iv contrast
Asthmatics and IV contrast
  • Risk of serious reaction increased 5-fold in patients with asthma, multiple allergies
  • Rate of serious reactions still sufficiently low (0.1%) that pre-medication not advised

Morcos SK. Br J Radiol. 2005 Aug; 78(932):686-93.

question 6
Question #6

Should we do a serum creatinine on everyone before they get an intravenous contrast load?

contrast induced nephropathy
Contrast Induced Nephropathy
  • Definition of CIN
    • Absolute  in Cr of 0.5mg/dL
    • Relative  of 25% in 48 hours
  • Biggest risk: preexisting  Cr
  •  exponentially with Cr
    • Baseline Cr <1.5 mg/dL: 2%
    • Baseline Cr >2.5 mg/dL: 20%

Moore RD, et al. Radiology. 1992 Mar; 182(3):649-55.

when to check creatinine
Age > 70 years

CHF

Cirrhosis

Diabetes

Multiple myeloma

Anemia

Sepsis

Hypotension

Hypertension

Nephrotoxic drug: NSAID, ACE inhibitor, furosemide

When to Check Creatinine
question 7
Question #7

Can I prevent contrast-induced nephropathy by giving the patient NAC or bicarb or something else?

what doesn t work
What DOESN’T Work

Diuresis: mannitol, furosemide

  • “Flush” contrast through kidneys
  • Intuitively make since
  • Actually increase CIN rate

Solomon R, et al. N Engl J Med 1994 Nov 24; 331(21):1416-30

what doesn t work1
What DOESN’T Work

Common vasodilators: dopamine, fenoldopam

  • Increase renal flow
  • Intuitively make since
  • Actually increase CIN rate

Stone GW et al. Rev Cardiovasc Med. 2001;2 Suppl 1:S31-6.

what doesn t work2
What DOESN’T Work

Other vasodilators: atrial natriuretic peptide, calcium channel blockers, ACE- inhibitors, endothelin receptor antagonists

  • Intuitively make since
  • Actually increase CIN rate
what doesn t work3
What DOESN’T Work

Aminophylline / theophylline

  • Several studies
  • Results conflicting

Pannu N et al. JAMA 2006 Jun 21; 295(23):2765-69

what doesn t work4
What DOESN’T Work

Aminophylline / theophylline

“Theophylline may reduce the incidence of CIN with an efficacy that is perhaps comparable to that reported in studies of N-acetylcysteine. However, findings are inconsistent across studies.”

Bagshaw SM, et al. Arch Intern Med. 2005 May 23;165(10):1087-93.

preventing cin
Preventing CIN

NSS better than D5½NS

  • 1620 patients for angiography
  • D5½NS: 2.0% incidence CIN
  • NSS: 0.7% incidence of CIN

Mueller C, et al. Arch Intern Med. 2002 Feb 11; 162(3):329-36.

preventing cin1
Preventing CIN

NaHCO3 better than NSS (??)

  • Replace 150mL in 1 liter D5W with three amps of NaHCO3
  • Infuse 3 mL/kg for 1 hour before and 1 mL/kg for 6 hours after contrast administration
  • CIN reduced from 13.6% to 1.7%

Merten GJ, et al. JAMA. 2004 May 19; 291(19):2328-34.

preventing cin2
Preventing CIN

N-acetylcysteine (NAC)

  • Suggest NAC does nothing to prevent CIN
  • Rather it interferes with proper measurement of serum Cr
  • DOE rather than POEM??

Hoffman U et al. J Am Soc Nephrol. 2004 Feb; 15(2):407-410.

preventing cin3
Preventing CIN

N-acetylcysteine (NAC)

  • 87 adults with renal insufficiency
  • Half received 900-mg injection of NAC one hour before and another immediately after contrast medium injected
  • Other half: hydration only

Poletti PA, et al. AJR Am J Roentgenol. 2007 Sep;189(3):687-92.

preventing cin4
Preventing CIN

N-acetylcysteine (NAC)

  • Serum creatinine and cystatin C measured at admission and on days 2 and 4 after CT
  • 25% or greater increase in SCr in 9/43 (21%) in control group and in 2/44 (5%) in NAC group

Poletti PA, et al. AJR Am J Roentgenol. 2007 Sep;189(3):687-92.

preventing cin5
Preventing CIN

N-acetylcysteine (NAC)

  • 25% or greater increase in cystatin C concentration in 9/40 (22%) in control group and in 7/41 (17%) in NAC group

Poletti PA, et al. AJR Am J Roentgenol. 2007 Sep;189(3):687-92.

cin conclusions
CIN: Conclusions
  • Virtually all studies require pretreatment 12 hours or more in advance of procedure
  • Hydration helps: no controversy
  • NAC impractical for EM practice, MAY help
  • Bicarbonate: no protection
  • Vitamin C: no protection
question 71
Question #7

What if my patient takes metformin?

metformin and iv contrast
Metformin and IV Contrast
  • Metformin-associated lactic acidosis (MALA): complication
  • Recommendation #1: withhold metformin 48h before IV contrast
  • Recommendation, modified: withhold metformin for 48h after IV contrast
metformin contraindications
Hypersensitivity

DKA

Diabetic coma

Chronic liver disease

CHF

Vitamin B-12 deficiency

Recent MI

Shock

Severe systemic disease

Pulmonary insufficiency

Metformin Contraindications
slide66
MALA

Comprehensive review: 18 cases

  • Literature review
  • Data reported to manufacturers
  • Reports to FDA

McCartney MM, et al. Clin Radiol. 1999 Jan; 54(1):29-33.

slide67
MALA
  • Most were taking metformin despite contraindications
  • Exactly one case of MALA reported in patient with normal renal function

McCartney MM, et al. Clin Radiol. 1999 Jan; 54(1):29-33.

mala conclusion
MALA: Conclusion
  • Although evidence is scanty, it is prudent to withhold metformin for 48 hours following contrast study
some final thoughts
Some Final Thoughts
  • Much has changed from early days of CT scanning
  • What was accepted ten years ago is no longer true
  • Talk with your radiologists about their comfort levels
some final thoughts1
Some Final Thoughts
  • There is probably no way to prevent allergic reactions
  • There may be no way to prevent CIN in ED patients
ad