Pediatric Appendicitis

  • Etiology: occurs over 24-36 hours: hyperplasia of lymphoid follicles / parasites / neuroendocrine (carcinoid) tumor -> distension of appendix -> ischemic mucosal damage -> bacterial overgrown and wall invasion -> transmural inflammation -> perforation
  • AXR: appendicolith in 15%, may have distal small bowel obstruction
  • US:
    — Normal appendix: compressible blind ending tubular structure originating from base of cecum that does not have peristalsis, transverse diameter is < 6 mm, no wall thickening, central echogenic line which is acoustic reflection from collapsed luminal interface — Note: terminal ileum can mimic appendix but has hypoechoic folds and has peristalsis — Acute appendicitis: noncompressible blind ending tubular structure with transverse diameter > 6 mm, appendiceal wall thickness > 3 mm, hyperemia on color doppler US, periappediceal hypoechoic halo from wall edema, periappendiceal hyperechogenicty from periappendiceal edema, appendicolith
    — Note: some say appendiceal transverse diameter of 6-8 mm is indeterminate for acute appendicitis and that appendiceal transverse diameter of > 8 mm is diagnostic of acute appendicitis
    — Perforated appendicitis: appendix may not be seen or may be decompressed with diameter < 6 mm, phlegmon with poorly defined bowel loops in right lower quadrant with increased echogenicity, mass of mixed echogenicity, focal bowel wall thickening, intraperitoneal fluid, loculated fluid, frank abscess
  • CT: diameter > 8 mm (diameter 6-8 mm is indeterminate), enhancing, appendicolith in 30%, periappendiceal fat stranding, periappendiceal fluid / abscess are signs of perforation
  • Clinical:
    — Simple appendicitis: periumbilical pain that localizes to right lower quadrant with fever and vomiting is seen in < 50% of patients, 33% of patients have nonspecific symptoms
    — Perforated appendicitis: pain relief then more generalized pain and fever and generalized peritonitis
AXR of appendicolith
AXR AP shows an oval-shaped calcification in the right lower quadrant just above the right iliac crest at the level of the L4 vertebral body.

Radiology Cases of Perforated Appendicitis

AXR of small bowel obstruction due to perforated appendicitis
AXR supine (left) shows multiple dilated loops of small bowel that have air fluid levels on the AXR upright (right). There is also a suggestion of a soft tissue mass in the right lower quadrant which is displacing the bowel loops medially.
CT of perforated appendicitis
AP radiograph of the right femur was unremarkable. Coronal STIR MRI of the right hip and femur was unremarkable aside from incidental bright pelvic free fluid noted just above the bladder. Coronal 2D reconstruction from a CT with IV and oral contrast of the abdomen shows a large complex fluid collection containing air and a central calcification in the right lower quadrant which was lying next to the psoas muscle.

Radiology Cases of Appendicitis in Morgagni Hernia

CXR of Morgagni Hernia that contained acute appendicitis
CXR PA shows the right heart border to be obscured and the lateral shows loops of bowel rising above the diaphragm anterior to the heart.

Gross Pathology Cases of Appendicitis

Pathologic image of acute appendicitis with appendicoliths
Pathological image with the appendix opened longitudinally shows it to be grossly inflamed with two appendicoliths within the lumen of the appendix.