Radiographic Evaluation of Acute Appendicitis

							Radiographic Evaluation of
    Acute Appendicitis


   Ryan Marlin
Radiology Clerkship
  February 2005
               Typical Case:
• 10 year old male patient with fever, nausea, vomiting,
  anorexia and right lower quadrant pain that began
  yesterday.

• Physical Exam: Temp = 38.5C, localized right lower
  quadrant pain with guarding on palpation of the
  abdomen, rebound tenderness

• Lab values: WBC = 12,000 with 70% neutrophils and
  15% bands.
   What do you do next?
A. Order a plain film upright
   radiograph of the abdomen
B. Order an Ultrasound of the
   abdomen
C. Order a CT of the abdomen
D. Order an MRI of the abdomen
E. Go straight to surgery
          ANSWER:



E. Go straight to surgery
 Acute Appendicitis: common things
           are common
• Most common surgical
  cause of acute abdominal
  pain – approx 250,000 new
  cases per year in the US

• Most common emergency
  surgical procedure in peds
  and adolescents

• Misdiagnosis is common:
  15%-33% of surgically
  removed appendices show
  no pathologic features of
  appendicitis
Problems with misdiagnosis
   or delayed diagnosis:
• Unnecessary Costs

• Unnecessary exposure to radiation

• Increased morbidity due to
  increased rates of perforation
  resulting from longer time to
  diagnosis and surgery
Time Delay in Appendicitis
 Diagnosis and Treatment




Lee SL, Walsh AJ, Jung SH. Computed Tomography and Ultrasonography Do Not Improve and May
Delay the Diagnosis and Treatment of Acute Appendicitis. Arch Surg 136:May 2001. p556-562
    Obstacles to Diagnosis
• Position of the appendix:
   – Size varies from 2-20cm
   – Tip can lie in retrocaecal, pelvic, subcaecal, preileal
     and post-ileal positions


• Closely mimicked by other common
  conditions: ureteral calculi, gynecological pathology
  such as acute salpingitis, ectopic pregnancy, etc.


• Age, gender and comorbidities:
  eg. Up to 45% of females of reproductive age
  are misdiagnosed
  Differential Diagnosis for Acute
            Appendicitis
Gastrointestinal            Gynecologic                   Pulmonary
Abdominal pain, cause       Ectopic pregnancy             Pleuritis
unknown                     Endometriosis                 Pneumonia (basilar)
Cholecystitis               Ovarian torsion               Pulmonary infarction
Crohn's disease             Pelvic inflammatory disease
Diverticulitis              Ruptured ovarian cyst
Duodenal ulcer              (follicular, corpus luteum)
                                                          Genitourinary
                                                          Kidney stone
Gastroenteritis             Tubo-ovarian abscess
                                                          Prostatitis
Intestinal obstruction
                                                          Pyelonephritis
Intussusception
Meckel's diverticulitis
                            Systemic                      Testicular torsion
                            Diabetic ketoacidosis         Urinary tract infection
Mesenteric
                            Porphyria                     Wilms' tumor
lymphadenitis
                            Sickle cell disease
Necrotizing enterocolitis
                            Henoch-Schönlein purpura
Neoplasm (carcinoid,                                      Other
carcinoma, lymphoma)                                      Parasitic infection
Omental torsion                                           Psoas abscess
Pancreatitis                                              Rectus sheath hematoma
Perforated viscus
Volvulus
        Physical Signs Associated with
       Appendicitis (what the books say)
Sign               Description

McBurney sign      Localized right lower quadrant pain or guarding on
                   palpation of the abdomen (the single most important
                   sign)
Psoas sign         Pain on hyperextension of right thigh (often indicates
                   retroperitoneal retrocecal appendix)
Obturator sign     Pain on internal rotation of right thigh (pelvic appendix)
Rovsing sign       Pain in the right lower quadrant with palpation of the left
                   lower quadrant
Dunphy’s sign      Increased pain in the right lower quadrant with coughing

Hip flexion        Patient maintains hip flexion with knees drawn up for
                   comfort
Other peritoneal   Rebound tenderness, hyperesthesia of the skin in the
signs              right lower quadrant
         History and Physical
Most common      Sensitivity   Specificity
Signs/Sx
Right lower         81%           53%
quadrant pain
Anorexia            68%           36%
Nausea              58%           37%
Fever               67%           79%
Pain Migration      64%           82%
               History and Physical
  Advantages:                                                    Disadvantages:
• Cheap, efficient, safe                                       • No single clinical
  and noninvasive                                                finding can
                                                                 effectively rule in or
• Surgical protocols                                             rule out appendicitis
  based on patient risk
  and H&P reduce use
  of imaging while                                             • Overall diagnostic
  increasing diagnostic                                          accuracy is only
  accuracy*                                                      approx 80%
 *Garcia Peña BM., Cook EF, Mandl, K. Selective Imaging
   Strategies for the Diagnosis of Appendicitis in Children.
   PEDIATRICS. 113( 1) Jan 2004, pp. 24-28
      Plain Film Radiography
• Not cost effective

• Not specific

• Can be misleading

• Not recommended
  unless other pathology is
  suspected: eg. perforation,
  intestinal obstruction,
  ureteral calculus
          Ultrasonography
 Advantages:                Disadvantages:
• Safe and Non-           • Sensitivity very
  invasive: No ionizing     dependent on
  radiation                 operator skill

• Cost-effective: cheap   • Greater potential for
  and can efficiently       false positives
  rule out other
  abnormalities           • Normal appendix
                            must be visualized to
• Very sensitive with a     rule out appendicitis:
  skilled technician:       Diagnosis limited by
  (71 to 97% accuracy)      position of appendix
          Ultrasonography




Transverse abdominal US demonstrates a
noncompressible mixed echotexture mass in the RLQ
consistent with appendiceal abscess/phlegmon.
Computed Tomography (CT)
  Advantages:              Disadvantages:
• More Precise than      • Radiation and/or
  US: less hospital to     contrast exposure:
  hospital variation       increased risk for
                           peds and pregnant
                           women
• More accurately
  identifies pathology   • Cost: relatively
                           expensive
• Reveals normal
  appendix better than   • Patient discomfort:
  US                       children often unable
                           to tolerate without
                           sedation
CT: Should it be the Gold Standard?
   According to one study:
   • Case series of 389 appendectomies between
     2000-2002
 Year        % Cases Diagnosed using CT                % Cases w/ normal pathology
2000                        52%                                        17%
2001                        74%                                         9%
2002                        86%                                         2%

   • The perforated appendicitis rate
     decreased from 25% in 2000 to 9%
     in 2002.*
        *Jones K, Pena AA, Dunn EL, Nadalo L, Mangram AJ. Are negative appendectomies still
        acceptable?Am J Surg. 2004 Dec;188(6):748-54
       Acute Appendicitis on CT


The arrow points to an
area of soft tissue
induration within the
retrocecal fat. There is
a rim like area of higher
attenuation within this
area that is fluid filled.




An axial slice of a CT scan done with intravenous and oral contrast
  that is compatible with a diagnosis of acute appendicitis. The
              presence of rupture cannot be excluded.
                MRI
• Low risk, no ionizing radiation

BUT……
• Relatively new modality: little data
• Expensive
• Not widely used and unnecessary
  The Big Picture:
Is US or CT better?
Predictive Probablility of US vs CT




      Terasawa T, Blackmore CC, Bent S, Kohlwes RJ. Systematic review: computed
      tomography and ultrasonography to detect acute appendicitis in adults and adolescents.
      Ann Intern Med. 2004 Oct 5;141(7):537-46
                      So is CT better?
• Many studies suggest that CT has better accuracy, but
  blinded prospective studies at community hospitals
  have found no difference between US and CT

• Metanalysis suggests that many studies that show the
  superiority of a modality are flawed and that diagnostic
  accuracy is inflated:
    – Most studies use different reference standards such as
      surgical confirmation, and clinical follow-up for patients
      with positive test results and those with negative results.

    – This can falsely overestimate test performance, including
      sensitivity and specificity


 Poortman P, Lohle PN, Schoemaker CM, Oostvogel HJ, Teepen HJ, Zwinderman KA, et al. Comparison of
 CT and sonography in the diagnosis of acute appendicitis: a blinded prospective study. AJR Am J Roentgenol.
 2003;181:1355-9.
   Rely on clinical judgment, NOT a
           “Gold Standard”
                                                              Protocols/Risk Stratification:
 Evidence suggests                                            • Increase diagnostic
 that surgical                                                  Accuracy
 protocols and risk
 stratification produce
 better results than                                          • Decreased rates of false
 relying solely on                                              positives
 imaging findings to
 guide clinical                                               • Decreased rates of
 decisions*                                                     missed appendicitis

*Garcia-Pena, BM et al. Selective Imaging Strategies for the Diagnosis of Appendicitis in Children. Pediatrics 113(1) Jan 04.
Garcia-Pena, BM et al. Effect of an Imaging Protocol on clinical Outcomes Among Pediatric Patients with Appendicitis.
Pediatrics 110(6). Dec 02.
  Examples of protocols and Risk
Stratification for Equivocal Patients
 Surgical Protocol             Risk Stratification
                                 Suspected Appendicitis
     Suspected                   Polys <67%        Polys >67%
    Appendicitis                 Bands <5%         WBC >10,000
                                 No Guarding        Guarding
                               Abdominal Pain <   Abdominal Pain
      Perform US                   13hrs             >13hrs

     +           --
Appendectomy  +  CT             Low Risk          High Risk
                      --
                                  US                   CT
                                +Surgery            + Surgery
      Observe/discharge Home
                                - Observe           - Observe
                         Example:
• Case Series: 1338
  children with          40%
  suspected appendicitis
                         35%
                                                          Perforation
                              30%
• US-CT protocol              25%
  implemented                                             Negative
                              20%                         appendectomy
                         15%
• 60% had equivocal
  Physical exam findings 10%
                          5%
• Patients w/ unequivocal     0%
  findings went straight to          Before     After
  appendectomy and had              Protocol   Protocol
  similar outcomes
                   Summary
• Imaging should be considered within the context of a
  good history and physical

• Evidence suggests that physician errors in diagnostic
  decision-making more often lead to misdiagnosis or
  delayed diagnosis of appendicitis than rates of US and
  CT use.


• Risk stratification based on clinical findings and use of
  imaging studies based on protocols reduces rates of
  inaccurate diagnosis and unnecessary use of imaging
  studies
              Conclusion
• There is currently no standardized
  protocol for diagnosis of acute
  appendicitis

• Diagnosis of Acute Appendicitis should
  include:
  – Accurate H&P, lab studies, urinalysis
  – Consideration of risk when exposing
    patients to unnecessary radiation
  – Selective use of US and CT
                                   References
Graff L. et al. False-negative and False-positive Errors in Abdominal Pain Evaluation: Failure to Diagnose
    Acute Appendicitis and Unnecessary Surgery. Acad. Emerg. Med. 7(11) 2000. pg 1245-1255.
Garcia-Pena, BM et al. Selective Imaging Strategies for the Diagnosis of Appendicitis in Children.
    Pediatrics 113(1) Jan 04.
Garcia-Pena, BM et al. Effect of an Imaging Protocol on clinical Outcomes Among Pediatric Patients with
    Appendicitis. Pediatrics 110(6). Dec 02.
Kaiser S, Mesas-Burgos C, Soderman E, Frenckner B. Appendicitis in children--impact of US and CT on
    the negative appendectomy rate. Eur J Pediatr Surg. 2004 Aug;14(4):260-4
Jones K, Pena AA, Dunn EL, Nadalo L, Mangram AJ. Are negative appendectomies still
    acceptable?Am J Surg. 2004 Dec;188(6):748-54
Lee SL, Walsh AJ, Jung SH. Computed Tomography and Ultrasonography Do Not Improve and May
    Delay the Diagnosis and Treatment of Acute Appendicitis. Arch Surg 136:May 2001. p556-562
Old JL, et al. Imaging for Suspected Appendicitis. Am Fam Physician 2005;71:p71-78
Poortman P, Lohle PN, Schoemaker CM, Oostvogel HJ, Teepen HJ, Zwinderman KA, et al. Comparison of
    CT and sonography in the diagnosis of acute appendicitis: a blinded prospective study. AJR Am J
    Roentgenol. 2003;181:1355-9.
Terasawa T, Blackmore CC, Bent S, Kohlwes RJ. Systematic review: computed tomography and
    ultrasonography to detect acute appendicitis in adults and adolescents. Ann Intern Med. 2004 Oct
    5;141(7):537-46