Imaging in Appendicitis


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Ultrasound and CT findings in Acute appendicitis

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Imaging in Appendicitis

  1. 1. ACUTE APPENDICITIS Dr. P.Sandeep
  2. 2. APPENDIX    The appendix arises from the posteromedial surface of the caecum, approximately 2-3cm inferiorly to the ileocaecal valve, where the taena coli converge. It is a blind diverticulum, which is variable in length from 2-20cm. The appendix lies on its own mesentery, the mesoappendix, within which run vessals and lymphatics.
  3. 3.  Location of the base of the appendix is relatively constant, located roughly between the iliocecal valve and the apex of the caecum. But the tip of the appendix can have a variable position within the abdominal cavity: a. b. c. d. e. behind the caecum (ascending retrocaecal) : 65% inferior to the caecum (subcaecal) : 31% behind the caecum (transverse retrocaecal) : 2% anterior to the ileum (ascending paracaecal preileal) : 1% posteior to the ileum (ascending paracaecal
  4. 4. Blood supply  Arterial - Appendicular artery, a branch of the Ileocolic artery (a derivative of the superior mesenteric artery)  Venous - similarly named veins draining to the portal venous system
  5. 5. Plain film  An appendicolith is seen in 10% of patients, with 90% going on to develop appendicitis some time in the future.  The appendix can fill with contrast during a barium enema study Ultrasound  Normal appendix is visible in 60% of children and thin adults.
  6. 6. CT:    The maximal normal appendiceal diameter is quite variable; although it usually is 7mm or less. The lumen of the normal appendix may fill with contrast material, or it may contain intraluminal air or fluid. In children who often have much less intraperitoneal and retroperitoneal fat to delineate the cecum and appendix compared with adults, it is difficult to differentiate the normal appendix from adjacent unopacified bowel loops.
  7. 7. CT scan after oral contrast administration shows normal appendix with intraluminal enteric contrast material and gas (arrows). Appendix wall is nearly imperceptibly thin
  8. 8. Appendicitis    Inflammation of the appendix. Acute appendicitis occurs when the appendiceal lumen is obstructed, leading to fluid accumulation, luminal distention, inflammation, and, finally, perforation. Obstruction may be caused by : a. b. c. d. e. lymphoid hyperplasia (60%) appendicolith foreign bodies Crohn's disease other rare causes, e.g. stricture, tumor, parasite
  9. 9.  Tip of appendix is often first site of inflammation and appendiceal perforation.
  10. 10.   Appendicitis traditionally has been a clinical diagnosis, many patients are found to have normal appendixes at surgery. However, negative laparotomy can be avoided in many patients if modern diagnostic methods are used to confirm or exclude acute appendicitis.
  11. 11. IMAGING Radiography: Non specific  Appendicolith in 5-10% of patients  Sentinel loop: dilated atonic ileum containing air-fluid levels.  Dilated caecum  Widening and blurring of properitoneal fat lin  Scoliosis with concavity to right  Right lower quadrant mass indenting on caecum  Loss of right psoas margin  Free peritoneal air very uncommon  With perforation    Small bowel obstruction RLQ extraluminal gas Displacement of bowel loops from RLQ
  12. 12. Fluoroscopy:  Barium Enema  Non-filling of appendix (normal in 1/3 of patients)  Focal mural thickening of medial wall of cecum ("arrowhead deformity")
  13. 13. Ultrasound: sensitivity of 85% and specificity of 92% The graded-compression technique of US is performed with a high resolution, linear array transducer  Non-compressible, blind-ending tubular structure.  The maximal appendiceal diameter, from outside wall to outside wall, is greater than 7 mm  Sonographic "McBurney sign" with focal pain over appendix  Target appearance : If fluid is present in the lumen, a fluid-filled center and surrounded by a echogenic mucosa and submucosa and hypoechoic muscularis, may be seen when imaging in the axial plane  Shadowing, echogenic appendicolith.  Increased periappendiceal echogenicity representing fat infiltration and enlarged mesenteric lymph nodes
  14. 14. Target sign
  15. 15. Appendicolith Longitudinal US scans through an inflamed appendix show an echogenic appendicolith with acoustic shadowing
  16. 16.  Perforation • • • Loss of the echogenic submucosal layer Presence of a loculated periappendiceal or pelvic fluid collection or abscess The appendix itself is visible in only 40%–60% of patients with appendiceal perforation.
  17. 17. Perforation Longitudinal and transverse US scans through an inflamed appendix show a diffuse hypoechoic and enlarged appendix (between electronic calipers), with loss of the normally echogenic submucosal layer. At surgery, appendiceal perforation was noted
  18. 18. Longitudinal US scan through the right lower quadrant shows an enlarged appendix (between electronic calipers) with surrounding loculated fluid. Appendiceal perforation was noted at surgery
  19. 19. Color Doppler:  Peripheral wall hyperemia, reflecting inflammatory hyperperfusion.    In early inflammation, color flow may be absent or limited to the appendiceal tip. Color flow may also be absent in gangrenous appendicitis. In appendiceal perforation  hyperemia in the periappendiceal soft tissues or within a well-defined abscess
  20. 20. Longitudinal and transverse US images through an inflamed appendix demonstrate marked hyperemia along the periphery
  21. 21. False-negative diagnosis: 1. Early inflammation is limited to the appendiceal tip, which can be missed if only the proximal appendix is Imaged.  visualize the entire length of the appendix. 2. Failure to visualize the appendix  Inability to compress the right lower quadrant adequately  Aberrant location of the appendix, such as retrocecal position.  can be minimized by having the patient identify the site of maximal tenderness and by scanning in a coronal plane with the transducer parallel to the iliac wing. If the psoas muscle is visualized, a retrocecal appendix should be seen  Appendiceal  perforation. Identification of secondary findings can help to suggest the
  22. 22. Distal appendicitis Transverse US image through the proximal appendix (between electronic calipers) demonstrates a normal appendiceal diameter less than 6 mm.. Transverse US scan through the distal appendix (between electronic calipers) demonstrates appendiceal enlargement. The distal appendix measures 8.1 mm.
  23. 23. False-positive diagnosis: 1. Normal appendix may be visible with gradedcompression  Measures 6 mm or less in maximal outer diameter, is compressible, and lacks adjacent inflammatory changes 2. Periappendiceal inflammation due to Crohn disease or pelvic inflammatory disease 3. Inflamed Meckel diverticulum 4. Spontaneous resolution of acute appendicitis
  24. 24. Normal appendix Longitudinal and transverse US images through the right lower quadrant demonstrate a normal appendix (between electronic calipers) measuring less than 6 mm in diameter.
  25. 25. CT Findings Sensitivity and specificity approaches 100% The highest diagnostic efficacy at CT has been obtained with the use of rectal contrast material and thin collimation through the lower abdomen and pelvis     Dilated appendix >7 mm Appendiceal wall thickening (≥3mm) and enhancement. Mural stratification of the appendiceal wall Circumferential or focal apical cecal thickening    useful in allowing diagnosis of acute appendicitis if there is difficulty in identifying an enlarged appendix Arrowhead sign: focal cecal wall thickening centered on the appendiceal orifice: enteric contrast material in the cecal lumen points to the abnormal appendix and assumes a triangular configuration The cecal bar sign: Inflammatory soft tissue at the base of the appendix that separates the appendix from the contrast-filled cecum.
  26. 26.  Appendicolith May be incidental finding  Retained barium can be differentiated from an appendicolith by viewing the digital scout radiograph, as retained barium will have a higher attenuation  may have prognostic importance : increases the likelihood of appendiceal perforation    Periappendiceal fat stranding Adjacent bowel wall thickening, free peritoneal fluid, mesenteric lymphadenopathy, intraperitoneal phlegmon, or abscess
  27. 27. Axial CT scan obtained through the lower abdomenwith thin collimation following the intravenous and rectal administration of contrast material demonstrates a contrast material–filled normal proximal appendix (arrow) (b)Axial CT image obtained 1 cm below ashows the normal contrast material– filled distal appendix (arrow)
  28. 28. Axial CT scan obtained through the lower abdomen with thin collimation following the intravenous and rectal administration of contrast material demonstrates an enlarged proximal appendix with intense enhancement of the appendiceal wall. Axial CT scan obtained 1 cm below ademonstrates intense contrast material enhancement of the distal appendix.
  29. 29. Axial CT scan obtained through the upper pelvis with thin collimation following the intravenous and rectal administration of contrast material demonstrates an appendicolith within the appendix (arrow)
  30. 30. Axial CT scan obtained through the upper pelvis with thin collimation following the intravenous and oral administration of contrast material demonstrates focal thickening at the cecal apex (arrow). Axial CT scan obtained 2 cm below shows an enlarged appendix (arrow)
  31. 31. 16-year-old girl with acute appendicitis. Axial CT after oral and IV contrast material shows cecal wall thickening around appendiceal orifice. Enteric contrast material in cecal lumen points to enlarged appendix (arrow) and assumes triangular
  32. 32. Complications  Perforation     Periappendiceal Abscess   defect in the enhancing appendiceal walL presence of localized periappendiceal inflammation presence of one or more appendicoliths in association with periappendiceal inflammation is virtually diagnostic of perforation loculated, rim-enhancing fluid collection that may have mass effect on adjacent bowel loops Peritonitis   interloop fluid and free-fluid tracking along the peritoneal reflections CE CT helps differentiate bacterial peritonitis from ascites by showing enhancement and thickening of peritoneal reflections, inflammatory changes in the mesentery and omentum, engorgement of regional mesenteric vessels, and hyperemic changes in contiguous bowel segments.
  33. 33. Pitfalls in the CT diagnosis of acute appendicitis 1. Overlapping range in maximal appendiceal diameter between inflamed and uninflamed appendices.  2. Inflamed appendix may be mistaken for unopacified bowel loops.  3. assess for associated secondary changes, including cecal apical thickening and infiltration of periappendiceal fat optimize cecal and colonic opacification Early appendiceal inflammation may be limited to the appendiceal tip.  identify the entire appendix at CT
  34. 34.  Bowel Obstruction   mechanical obstruction, likely secondary to entrapment of the distal ileum in a periappendiceal inflammatory mass Gangrenous Appendicitis Gangrenous appendicitis is the result of intramural and arterial thromboses.  pneumatosis,  shaggy appendiceal wall,  patchy areas of mural nonperfusion. 
  35. 35. Axial CT scan obtained through the upper pelvis with thin collimation following the intravenous and rectal administration of contrast material demonstrates a normal-appearing proximal appendix originating from the cecal apex (arrow).
  36. 36. Axial CT scan obtained through the upper pelvis with thin collimation following the intravenous and rectal administration of contrast material demonstrates focal cecal apical thickening (arrow). Axial CT scan obtained 1 cm below ademonstrates an enlarged curvilinear appendix (arrow). Note that there is not a good plane of separation between the appendix and adjacent unopacified small bowel loops. The cecal apical thickening was helpful in calling attention to the abnormal appendix.
  37. 37. 6-year-old girl with acute appendicitis. CT scans obtained before and after IV contrast administration. Unenhanced scan is indeterminate because appendix is not confidently visualized. Enhanced scan shows dilated appendix with thickened, hyperenhancing wall
  38. 38. Advantages of US:  Lower cost  Lack of ionizing radiation  Ability to assess vascularity through color Doppleranalysis  Provide dynamic information through graded-compression  Delineate gynecologic disease which is a common mimic of acute appendicitis. Advantages of CT:  Less operator dependency than US.  Higher diagnostic accuracy.  Enhanced delineation of disease extent in perforated appendicitis.  Valuable in obese patients, since they are typically difficult to evaluate with US.
  39. 39. Differential Diagnosis 1. 2. 3. 4. 5. 6. Mesenteric Adenitis Cecal Diverticulitis Epiploic Appendagitis Crohn’s Disease Infectious Terminal Ileitis Appendiceal Mucocele
  40. 40. REFERNCES   Carlos J. Sivit, MD, Marilyn J. Siegel, MD, Kimberly E. Applegate, MD Kurt D. Newman, MD : When Appendicitis Is Suspected in Children. Pinto Leite et al : CT Evaluation of Appendicitis and Its Complications: Imaging Techniques and Key Diagnostic Findings