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Pediatric Appendicitis

DDX of RLQ pain:
- Appendicitis
- Intussusception
- Inflammatory bowel disease
- Meckel's diverticulum
- Malrotation
- Enteric duplication cyst
- Ingested foreign body
- Omental infarction
- Gastroenteritis
- Peptic ulcer disease
- Pyelonephritis
- Gynecologic disorders in females

1. Appendicolith - seen in only 10-15% of cases
2. Ileus - secondary to inflammation
3. SBO - secondary to appendiceal rupture (a perforated appendix is the most common cause of distal SBO in children less than three years of age)
4. Free air in cases of ruptured appendix - very rare

Sonography may also be used to evaluate gynecological abnormalities which may clinically simulate appendicitis in female patients. The disadvantages of ultrasound are its operator dependence and the inconsistent visualization of a normal appendix.

Normal appendix can be seen as tubular, blind-ended, attached to the cecum and relatively mobile, with a length of 5 to 10 centimeters and a maximum diameter of < 5 millimeters. Its normal three layers can be seen as concentric rings of alternating echogenicity when viewed in cross-section.

Sonographic signs of acute appendicitis include:

1.Tubular structure
3.Attached to cecum
4.Distension (diameter >6mm)
5.Lack of compressibility
7.Pelvic abscess (with perforation)

Interruptions in the hyper-echoic submucosal layer may indicate wall necrosis or perforation. Enlargement of the ileocolic mesenteric nodes is common, although not specific for appendicitis. Color Doppler interrogation may also be useful to demonstrate increased blood flow/hyperemia of the bowel wall which has been described with acute appendicitis.

If the initial search for findings of appendicitis is negative, it is prudent to evaluate the remainder of the abdominal and pelvic organs for other potential etiology of abdominal pain.

Causes of false negative results on US include:

1.Perforation of the appendix with accompanying decompression
2.Retrocecal appendix
3.Focal inflammation limited to the tip of the appendix
4.Shadowing of the appendix by intestinal gas

False positive results on US may be due to:

Secondary appendiceal enlargement due to other primary inflammatory condition such as inflammatory bowel disease or perforated peptic ulcer.

In cases of complicated appendicitis (ruptured appendix or peri-appendiceal abscess), or for an older or obese child, CT may be the modality of choice. Some studies contend that CT rather than ultrasound should be used in all patients as it is less operator-dependent, but most authors who focus on children advocate using ultrasound in at least one arm of their imaging algorithm. The disadvantages of CT in pediatric patients are the use of ionizing radiation and poorer inherent tissue contrast due to the typical lack of mesenteric fat in young children.

CT findings of acute appendicitis might include:

1.Appendiceal enlargement
2.Periappendiceal fat stranding
3.Thickened cecal wall
6.Mesenteric lymphadenopathy
7.Fluid collections - secondary to rupture of the appendix

Free air is very rarely present with rupture of the appendix, however CT is very sensitive in its detection

Treatment for acute appendicitis is surgical appendectomy. In subacute cases with abscess formation and ruptured appendix, initial non-operative management with IV antibiotics and subsequent elective surgery may be the chosen course of action. Imaging-guided drainage of a percutaneously accessible abscess may also be considered. CT or ultrasound are essential in guiding drainage procedures, and CT is often used in post-surgical or post-drainage follow-up.

Plain abdominal radiographs are often the first line of imaging in the setting of right lower quadrant pain. Following this, US or CT may be used.

US has the highest yield in:

2.Younger children
3.Those with symptoms lasting no longer than 1-2 days
4.Cases with clinical suspicion for gynecologic pathology

CT has the highest yield in:

2.Obese patients
3.Older children/adolescents (where graded compression US may be more difficult because of larger body size)
4.Those with prolonged symptoms lasting more than 2-3 days

Ultrasound has its optimal yield in acute appendicitis and CT in complicated or prolonged appendicitis.