II. Indications

  1. Suspected Appendicitis

III. Precautions

  1. Consider Bedside Ultrasound in the emergency department
  2. Appendix Ultrasound can be used to diagnose Appendicitis, but not exclude Appendicitis
    1. Negative Ultrasound may require additional imaging (e.g. CT Abdomen, MRI Appendix)
    2. Positive Ultrasound, diagnostic for Appendicitis
      1. Spares additional imaging (and radiation exposure) prior to appendectomy
  3. Perform at centers where ultrasonographer and radiologist are highly skilled at Ultrasound evaluation of appendix
    1. Imaging study of choice for children with suspected Appendicitis if experienced Ultrasound staff
      1. RLQ Abdominal Ultrasound has a high Test Specificity and Test Sensitivity for Appendicitis in children
    2. CT Abomen is recommended instead if appendix abscess is suspected

IV. Technique

  1. Systematic approach is important (see videos by Adam Sivitz, MD)
  2. Make the patient comfortable
    1. Pretreat with Opioid Analgesics to allow for adequate compression with Ultrasound
    2. Consider anxiolysis
    3. Consider distracting toy or movie for a child
  3. Start with curvilinear probe (abdominal probe or cardiac probe)
    1. Used in Approach 2 (see below)
    2. Evaluate differential diagnosis
      1. RUQ Ultrasound for Gall Bladder
      2. Pelvic Ultrasound for Ovarian Cyst
      3. Limited Ultrasound for Acute Renal Colic
    3. Identify landmarks for appendix scan
      1. Iliac vessels (medial to appendix)
      2. Psoas muscle (deep to appendix)
      3. Ascending colon
        1. Lacks bright hyperechoic rings of plica circularis seen in Small Intestine
      4. Bladder
        1. Consider using as acoustic window to visualize retrocecal appendix
  4. Linear probe (images down to 6 cm depth)
    1. Approach 1: Based on Cecum Identification (Adam Sivitz, MD method)
      1. Identify Large Bowel in RLQ (haustra, no peristalsis) with transverse linear probe
        1. Follow Large Bowel inferiorly with underlying psoas muscle
      2. Rotate probe to long axis and move medially toward cecum
        1. Identify boundary of Small Bowel (peristalsis) and Large Bowel
    2. Approach 2: Based on curvilinear probe landmarks (see above)
      1. Position patient with right leg over left (brings right psoas muscle anterior)
      2. Start at region of maximal pain with probe indicator at 12:00
      3. Slowly scan in both longitudinal and transverse approaches across the right lower Abdomen
        1. Covering the area in lawnmower-like swaths
    3. Apply graded compression with Ultrasound probe
      1. Slowly increasing pressure displaces bowel gas
    4. Apply posterior manual pressure
      1. Hand behind patient's low back and push anteriorly
    5. Observe for blind-ended tubular structure
      1. See Interpretation below

V. Interpretation

  1. Normal appendix (difficult to visualize on Ultrasound)
    1. Blind-ended structure
    2. Wall appears as 3 white lines separated by hypoechoic layers
    3. Five layers (from inner to outer)
      1. Mucosa-lumen interface (most echogenic, inner-most layer)
      2. Mucosa (hypoechoic)
      3. Sub-Mucosa (echogenic)
      4. Muscularis propria (hypoechoic)
      5. Serosa (echogenic)
  2. Signs suggestive of Appendicitis
    1. Dilated, non-compressible blind-ended structure
      1. Outer appendix diameter (cross-section) 7 mm or greater
      2. Appendicolith may be found within lumen (non-compressible)
      3. Typically lacks peristalsis
    2. Peri-appendix changes
      1. Free fluid may surround area
      2. Fat stranding
        1. Edema and hyperechoic heterogeneous peri-appendiceal fat
    3. Appendix wall changes
      1. Thickened, edematous appendix wall
      2. Ring of Fire Sign
        1. Appendix outer wall hyperemic on color power doppler
  3. Signs suggestive of perforated appendix
    1. Loculated pericecal fluid
    2. Phlegmon
    3. Appendiceal abscess
    4. Pericecal fat
  4. Causes of false positive Ultrasounds
    1. Meckel's Diverticulum
    2. Pelvic Inflammatory Disease
    3. Endometriosis
    4. Cecal Diverticulitis
    5. Inflammatory Bowel Disease

VI. Efficacy

  1. Identifies alternative diagnoses
  2. Very operator dependent
    1. Steep learning curve for both ultrasonagrapher and radiologist
  3. Test Sensitivity for acute Appendicitis
    1. Radiology performed: 72-88%
    2. Emergency Bedside Ultrasound: 65% (Test Specificity 90%)
      1. Fox (2008) Eur J Emerg Med 15(2): 80-5 [PubMed]
    3. Test Sensitivity may increase for perforated appendix
  4. Conditions with decreased efficacy
    1. Overweight
    2. Female
    3. Retrocecal appendix

VIII. References

  1. Claudius and Seif in Herbert (2013) EM:Rap 13(11): 1-3
  2. Majoewsky (2013) EM:Rap 13(10):11

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