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Imaging for Acute Appendicitis Navy Emergency Medicine PowerPoint Presentation

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  • Slide 1 - Imaging for Acute Appendicitis LT David Bruner LCDR Todd Parker Staff Emergency Physicians April 2009
  • Slide 2 - Objectives Cases Consider what you would do Imaging choices US CT Non-contrast vs oral contrast vs rectal MRI Reconsider Cases/Discussion
  • Slide 3 - Case 1 15 yo male - 1 day worsening abdominal pain Periumbilical  migrated to RLQ Nausea, vomiting, anorexia, hurts to walk, no fever RLQ guarding / rebound / Heel Tap / Rovsing Labs: WBC – 8.9 H/H – 12/37 UA – 12 WBC, Pos Leuk Est, rare bacteria What imaging, if any?
  • Slide 4 - Case 2 8 yo f - >24 hrs of worsening RLQ pain Diarrhea and nausea, subjective fever Urinary frequency / abdominal pain with micturition T – 101.0 P – 121 BP – 108/62 RLQ TTP at McBurney’s point Guard/mild rebound UA Negative WBC – Pending
  • Slide 5 - Case 3 37 yo man - 30 hours of worsening RLQ pain N/V and Fever to 100.5 No urinary symptoms PMHx of kidney stones – but this is different Wife and daughter recently sick with N/V/D RLQ TTP with guarding and rebound UA Negative Does he need a CT? If so, what kind
  • Slide 6 - Case 4 31 yo female - 2 days worsening pain Epigastric at first, now only RLQ Nausea, subjective fever, menses No urinary symptoms Positive McBurney’s, Rovsing, Heel Tap No CMT or adnexal masses felt HCG negative, UA negative Imaging?
  • Slide 7 - Case 4-1 Same as Case 4 except . . . . No vaginal bleeding HCG Positive ED US reveals IUP at 10 weeks Imaging?
  • Slide 8 - Case 5 73 yo female 30 hours lower abdominal pain and nausea No vomiting /diarrhea, fever, bloody stool, or dysuria Hx of HTN Otherwise negative PMHx and PSHx Bilateral Lower Quad TTP R > L, mild guarding P – 98 T – 100.8 BP – 135/76
  • Slide 9 - Clearly Imaging Reduces NAR Acceptable Negative Appendectomy Rate (NAR)? Historically 10-20% Higher % acceptable in women and peds With increased imaging 5-10% NAR Significantly increased pre-operative CT From 32% to 95% - Wegner study Wagner et al., Surgery. 2008; 144(2) Retrospective review of four-year time periods before and after frequent CT NAR decreased 16% to 6% NAR decreased mostly due to adult women No change in NAR with kids (8%) Adult male decreased from 9% to 5% (NSS) Adult women decreased 20% to 7% Kim, K. et al, “The Impact of Helical CT on Negative Appendectomy Rate: A Multi-Center Comparison; JEM 2008; 34(1) CT Rate and NAR inversely related NAR decreased 20% to 6% Limited by no follow up on negative scans Guss et al., “Impact of Abdominal Helical CT on the Rate of Negative Appendicitis” JEM 2008; 34(1) Retrospective review of before and after frequent CT Decrease in NAR from 15.5% to 7.6% 12% CT rate before readily available, 81% after
  • Slide 10 - Ultrasound Very safe! No radiation, no contrast required Sensitivity and Specificity: Adult - Sensitivity – 74-83%, Specificity – 93-97% Pediatrics – Sensitivity -88%, Specificity – 94% Variables: Body habitus, Location, Skill If can’t visualize – need to move on to the next step Findings on US for appendicitis Non-compressible appendix Appendix >6mm diameter Signs of perforation Free fluid Abscess
  • Slide 11 - Computed Tomography High overall accuracy, Sens, Spec, NPV, and PPV Available at all hours Risks: Radiation Contrast problems Allergic reactions Nephrotoxicity
  • Slide 12 - Oral Contrast Pros Sensitivity 94-98% / specificity 95-99% Alternative diagnoses May see extravasation Better if little intra-abdominal fat Fluid collections Comfort with reading contrasted vs non-contrasted Cons Large volume contrast What if vomiting? If not, probably will Risk of aspiration Aren’t they NPO? Increases difficulty of assessing bowel wall 2 hour delay Delays surgical decision Risk of perforation 4-8 hrs to advance
  • Slide 13 - Rectal Contrast CT Gravity drip – little risk of perforation Few minutes to perform scan As little as 15 minutes Accuracy equal to oral contrast No reported increased discomfort
  • Slide 14 - Rectal contrast study Berg ER, et al, Acad Emerg Med. 2006 Oct; 13(10) Compared oral and rectal contrast CT in a randomized trial Showed decreased length of stay in the ED by one hour No increased patient discomfort between oral or rectal contrast Equal diagnostic accuracy. Stephen AE, et al., J Ped Surg. Mar 2003; 38(3) 96/283 kids had rectal contrast 95% Sens and PPV Missed cases still went to OR because of clinical scenario
  • Slide 15 - Non-Contrast CT For diagnosis of appendicitis No need to drink contrast – no delay No change in diagnostic accuracy with IV Contrast Sensitivity 94-98% Specificity – 95-99% Significant supporting evidence for non-contrast CT in suspected appendicitis
  • Slide 16 - Lane MJ, et al, Radiology. 1999; 213 300 consecutive patients Non-contrast CT for appendicitis Compared with surgical pathology results 96% sensitive 99% specific 97% accuracy “Stacked the Deck”
  • Slide 17 - Hoecker CC, et al, JEM. May 2005 Retrospective study 112 children Atypical presentation (13% of total abd pain pts) CT’d without PO contrast (helical CT) 40% positive appendicitis rate Compared to those given PO contrast (prev studies) Equal sensitivity and specificity in both groups Overall 91% diagnostic accuracy
  • Slide 18 - Lowe LH, et al., Am J Roent. Jan 2001 Retrospective cohort of 72 children with non-contrast CT (atypical PE) 97% sensitive (95% CI, 91-100%) 100% specific (95% CI, 96-100%) Only took 5 minutes to perform the study
  • Slide 19 - Lowe, L. H., et al, Radiology 2001; 221 75 consecutive patients - non-contrast CT Atypical/Equivocal PE findings Compared residents’ and attendings’ reads Results: 91% agreement in reading studies 96% specificity and 88% accuracy in residents 98% specificity and 97% accuracy in attendings Attendings more confident of reads
  • Slide 20 - Ege G, et al., Br J Radiology. 2002; 75 296 adults non-con CT for suspected appendicitis Equivocal Exams Only 45% positive for appendicitis Compared with surgical pathology or follow up 96% sens and 98% spec/ 97% PPV and 98% NPV Recommends non-con CT for diagnosis of appendicitis in adults Negative study requires observation or follow up
  • Slide 21 - Systematic review of 23 studies (19 prospective, 4 retrospective) Over 3700 patients over 16 years old Anderson BA, et al, Am J Surg. Sep 2005
  • Slide 22 - IV Contrast Basak S, et al., J Clin Imag. 2002; 26. Performed study without contrast then with contrast No difference in making the diagnosis with IV or no contrast Some even thought IV obscured the intra-abdominal structures Keyzer, C., et al, Am J Roent. August 2008 Equal agreement between resident and attending reads Equal ability to visualize the appendix
  • Slide 23 - Alternative Diagnoses? Likely the most compelling argument What are the data? No good head to head studies Plenty of data showing that both enhanced and unenhanced find alternative diagnoses Which is best?
  • Slide 24 - Alternative Diagnoses in Non-Contrasted Studies Malone, A. et al, Am J Roentgen 1993 35% alternative diagnosis Diverticulitis, Ovarian Cysts or masses, PID, IBD Lane MJ, et al, Radiology. 1999 21% alternative diagnosis Ureteral Calculi, Diverticulitis, Chron’s, Mesenteric Adenitis, Neoplasms Alternative diagnoses advocated by IV and Oral/Rectal contrast Epiploic appendagitis, diverticulitis, Meckel’s Torsion, gynecologic disorders, obstructive uropathy, RLL PNA How much advantage does contrasted vs non-contrasted study provide?
  • Slide 25 - Why Scan at All? Kalliakmans V, et al., Scan J Surg. 2005; 94(3) 717 adults evaluated for appendicitis by 6 surgeons Normal practice patterns - recorded decisions 11% Negative appendectomy rate based on history, physical, and labs CT did not change diagnostic accuracy except in cases of atypical history and physical Recommends only using CT in equivocal cases
  • Slide 26 - CT in Pediatrics Increased lifetime cancer risk Less intra-abdominal fat Is a negative CT enough? Garcia K, et al, Radiology. Feb 2009 1139 pediatric cases over 4 years CT results compared to surgical pathology or follow up All except 8 had CT with IV contrast only NPV (non-visualized appendix) – 98.7% NPV (Visualized) – 99.8% NPV (Partially visualized) – 100%
  • Slide 27 - What About MRI? Pros: No radiation and can do reconstructions Cons: Cost, Time, not always available 24/7 Highly accurate, operator dependent Sensitivity 93-99% Specificity 94-100% Less robust evidence, but most studies show reliable and reproducible diagnostic accuracy Caution with gadolinium if pregnant
  • Slide 28 - Pregnancy and Appendicitis Same incidence as non-pregnant Questionable evidence of appendix moving out of RLQ Risk of surgery/anesthesia is less than risk of mortality to mother and fetus if appendicitis is missed or perforation occurs Want to avoid radiation risks to fetus – right? US may miss appendix in a different location MRI has good sensitivity and specificity in appendicitis Pedrosa, I et al, Radiology. Mar 2006 51 consecutive pregnant pts suspicion for appendicitis Underwent MRI if US inconclusive 4 had appendicitis – MRI correctly dx all 3 inconclusive – clinically resolved spontaneously Sens – 100% / Spec – 93.6% / Accuracy – 94% Pedrosa, I et al, Radiology. Mar 2009 148 consecutive pregnant pts suspicion for appendicitis Underwent MRI, 140/148 had ultrasound first 14 had appendicitis – MRI correctly dx all, U/S 5/14 9 False-Positives Sens – 100% / Spec – 93% / PPV – 61% / NPV – 100%
  • Slide 29 - Cases What did you decide to do?
  • Slide 30 - Case 1 – 15 yo male with 1 day of pain, migration, and peritonitis No imaging – take to the OR Kalliakmans V, et al., Scan J Surg. 2005; 94(3 Guss DA, et al., JEM. 2008; 34(1) Wagner PL, et al., Surgery. 2008 Aug; 144(2) All showed no improved negative appy rate for males with pre-operative CT scanning. “The routine use of CT for adult male and pediatric patients with a clinical picture suggestive of acute appendicitis should therefore be discouraged.”
  • Slide 31 - Case 2 – 8 yo girl, 1 day of pain, peritoneal signs, fever Actual case US done first Then an MRI was performed Then went to the OR Recommendation in this case US or straight to the OR CT vs MRI if still unsure
  • Slide 32 - Another case 13 year old girl Ultrasound Positive Appy Straight to the OR
  • Slide 33 - Case 3 – 37 yo male, 36 hours of pain, RLQ ttp, fever, hx of stones Non-contrast CT What if his WBC count was 19.5 with a left shift? No imaging . . . To the OR?
  • Slide 34 - Case 4 – 31 yo female, good exam, negative urine Do you want to avoid radiation? Could start with US Could go directly to CT Little reason for MRI
  • Slide 35 - Case 4-1 - Pregnant US first MRI vs CT Serial exams Dose of radiation thought to be teratogenic and increase risk of cancer in fetuses is 50 mGy ACOG gives CT a level 2 recommendation - Must weigh risks and benefits Patel SJ, Reede DL, Katz DS, et al., RadioGraphics. 2007; 1705-22. McCollough CH, Schuler BA, Atwell TD, et al., Radiographics. 2007; 27:909-918. Ratnaplalan S, Bona N, Chandra K, American Journal of Roentgenography. 2004 May; 182:1107-9. American College of Radiology. ACoR 04-05 bylaws. Reston, VA: American College of Radiology, 2005. ACOG Committee on Obstetric Practice. Guidelines for Diagnostic Imaging during Pregnancy. ACOG Committee Opinion no 299, September 2004. Obstetrics and Gynecology 2004; 104:647-651.
  • Slide 36 - Case 5 – 73 yo woman Non-contrast CT What if her Creatinine is 2.2? Does she need IV Contrast
  • Slide 37 - Take home points Classic presentations do not require imaging Reserve imaging for equivocal cases Abdominal CT estimated increase cancer risk 1 in 2000 CT not shown to decrease NAR in men and children Multiple studies suggest oral contrast provides no added value – no need to make them drink Consider US first for kids, women, and pregnant MRI is a reasonable alternative if available Can CT pregnant women safely – inform of risks Consider Informed Consent in certain cases
  • Slide 38 - Discussion

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