A Pediatric Radiology Textbook and Pediatric Radiology Digital Library
Pediatric Appendicitis
Etiology: — Obstruction of the appendiceal lumen by calcified fecolith or stool — Occurs over 24-36 hours: hyperplasia of lymphoid follicles or parasites or neuroendocrine (carcinoid) tumor leads to distension of appendix leads to ischemic mucosal damage leads to bacterial overgrown and wall invasion leads to transmural inflammation leads to perforation
Note: Obstructing appendicoliths cause appendicitis however not all appendicoliths are obstructing
Imaging AXR: — Appendicolith in 15% — May have distal small bowel obstruction
Imaging US Normal Appendix: — Compressible blind ending tubular structure originating from base of cecum that does not have peristalsis — Transverse diameter is less than 6 millimeters — No wall thickening — Central echogenic line which is acoustic reflection from collapsed luminal interface — 80% draped over iliac vessels
Note: Terminal ileum can mimic appendix but has hypoechoic folds and has peristalsis
Imaging US Acute Appendicitis: — Noncompressible blind ending tubular structure with transverse diameter greater than 6 millimeters — Appendiceal wall thickness greater than 3 millimeters — Hyperemia on US Color Doppler — Periappediceal hypoechoic halo from wall edema — Periappendiceal hyperechogenicty of periappendiceal fat in mesentery from periappendiceal edema — Appendicolith — Note: Most predictive ultrasound signs of acute appendicitis are transverse diameter greater than 6 millimeters (the larger the diameter, the more specific), echogenic periappendiceal fat, non-compressible appendix — Note: Transverse diameter should not be only criteria, some say appendiceal transverse diameter of 6-8 millimeters is indeterminate for acute appendicitis and that appendiceal transverse diameter of greater than 8 millimeters is diagnostic of acute appendicitis
Imaging Enema: — No longer done — Approximately 10% of normal appendices do not fill with contrast
Imaging CT Acute Appendicitis: — Transverse diameter greater than 8 millimeters (transverse diameter 6-8 millimeters is indeterminate) — Enhancing — Periappendiceal fat stranding — Appendicolith in 30% — Periappendiceal fluid and abscess are signs of perforation — Note: In patients with cystic fibrosis the appendix can have a larger than normal diameter
Imaging MR Normal Appendix: — Transverse diameter less than 7 millimeters — No periappendiceal changes — Paucity of fat can make visualization difficult so lack of inflammatory changes implies a normal exam
Imaging MR Acute Appendicitis: — Transverse diameter greater than 7 millimeters — Periappendiceal inflammation — Focus of diminished signal intensity represents an appendicolith
Note: Acute appendicitis rarely causes bowel wall thickening so if you see this think of infectious or inflammatory colitis
Note: Tip appendicitis is uncommon entity and is often over-diagnosed on imaging and is difficult to diagnose because of short affected segment
Note: Appendix can also be located in retrocecal region and pelvis
Note: When imaging patients with history of gastroschisis, omphalocele, malrotation, heterotaxy, the appendix is usually not in the right lower quadrant
Imaging US Perforated Appendicitis: — Appendix may not be seen or may be decompressed with diameter less than 6 millimeters — 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
Note: Imaging not sensitive for detection of perforated appendicitis
Note: Specific signs of perforated appendicitis are abscess, free air, disruption or discontinuity of appendiceal wall, free appendicolith which can cause recurrent and residual infection and predisposes patient for abscess
DDX: — Crohn disease can affect appendix so look for other findings of inflammatory bowel disease to distinguish from acute appendicitis — Lymphoid hyperplasia of appendix where appendix appears with a thickened hypoechoic appendiceal wall on ultrasound — Appendiceal carcinoid — Meckel diverticulitis can have similar appearance on ultrasound to acute appendicitis as inflamed blind-ending tubular structure so best way to prove it is not appendicitis is to identify its origin from ileum or see a normal appendix — Lower lobe bacterial pneumonia – check lungs on CXR and AXR and CT
Complications: Can serve as lead point for intussusception
Treatment: Ultimately surgical
Clinical: — Simple appendicitis: Periumbilical pain that localizes to right lower quadrant with fever and vomiting is seen in less than 50% of patients, 33% of patients have nonspecific symptoms — Perforated appendicitis: Initial pain then pain relief then more generalized pain and fever and generalized peritonitis — Appendicitis is uncommon in very young children, this along with their inability to provide history makes it difficult to diagnose and because of this young children with appendicitis present later and are more likely to have complications such as perforation
Radiology Cases of Appendicitis
Radiology Cases of Normal Appendix
Axial CT with intravenous and oral contrast of the abdomen shows a non-dilated tubular structure originating from the cecum filled with oral contrast and lying on top of the right psoas muscle with no inflammatory changes around it.
Radiology Cases of Normal Appendix in Cystic Fibrosis
Axial CT with contrast of the abdomen (above left) shows a low density liver due to fatty infiltration and a low density pancreas with calcifications that has a round low density fluid collection near the pancreatic head. The appendix in the right lower quadrant posterior to the cecum is dilated in diameter up to 10 mm but has no periappendiceal inflammation (above right and below). There is stool mixed with air in the terminal ileum medial to the cecum (above right and below).
Radiology Cases of Acute Appendicitis With 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.AXR supine shows two round radiopaque objects projecting over the right side of the middle and lower sacrum.Sagittal US of the right lower quadrant (above) shows a dilated, non-compressible, blind ending tubular structure measuring 10 mm in diameter with an echogenic focus at its tip causing posterior shadowing. Transverse US of the cecum (below) shows it to be thickened in appearance.Axial CT with contrast of the abdomen shows in the right lower quadrant an extremely large, fluid-filled, tubular structure containing several punctate calcifications within it and having some inflammatory changes surrounding it.
Radiology Cases of Acute Appendicitis
Transverse US of the right lower quadrant (above) shows a dilated, blind ending, non-compressible tubular structure (between the calipers) that is draped across the right psoas muscle and whose tip lies just above the right iliac vessels. Sagittal US of the right lower quadrant (below) showed the tubular structure to have a diameter of 9 mmSagittal US of the right lower quadrant shows a noncompressible blind ending J-shaped tubular structure (in the upper half of the image) with a transverse diameter of 8 mm with periappendiceal hyperechogenicty of the periappendiceal fat.
Radiology Cases of Acute Appendicitis in Morgagni Hernia
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.
Radiology Cases of Acute Appendicitis and Carcinoid Tumor of the Appendix
Axial CT with contrast of the abdomen (above) shows on top of the right psoas muscle and right iliac vessels in the right lower quadrant a dilated, fluid-filled tubular structure containing a calcification . Coronal CT (below) shows two calcifications within the tubular structure which is just medial to the cecum and surrounded by inflammatory changes.
Radiology Cases of 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.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 Perforated Appendicitis With Appendicolith
Sagittal US of the right lower quadrant (above left) shows a dilated, non-compressible, blind ending tubular structure between the calipers while a transverse US of the right lower quadrant (above right) shows echogenic fat surrounding an oval echogenic structure in the center of the image that has posterior shadowing. Axial CT with intravenous and oral contrast of the abdomen (below) shows a large cystic and septated mass in the center of and to the right of the pelvis that has an oval calcification in it anteriorly.
Radiology Cases of Perforated Appendicitis Causing Abdominal Abscess
Axial CT with contrast of the abdomen and pelvis shows low density fluid collections with enhancing rims anterior to the spleen (above), in the right pelvis (middle) and posterior to the bladder and anterior to the rectum (below).
Radiology Cases of Perforated Appendicitis Causing Retroperitoneal Fasciitis
Axial (above), coronal (below left) and sagittal (below right) CT without contrast of the abdomen shows a large of amount of air in the right posterior pararenal space with associated fat stranding. The appendix was normal in size and there was an appendicolith that was outside of the appendix (not provided).
Surgery Cases of Appendicitis
Surgical image shows the appendix to be grossly inflamed with exudate, but not to be perforated.
Gross Pathology Cases of Appendicitis
Pathological image with the appendix opened longitudinally shows it to be grossly inflamed with two appendicoliths within the lumen of the appendix.
Histopathology Cases of Appendicitis
Histopathological image of lower power, H&E stained section shows transmural inflammation with mucosal ulceration and serosal reaction with acute inflammatory exudate.Histopathological image of higher power H&E stained section shows the prominence of neutrophils.
