Acute Appendicitis In Children

Appendicitis is the commonest surgical emergency in children, with a lifetime risk of 7 to 9% and a peak incidence at 10 to 12 years (rare under 3 years, about 1 to 2% of cases).

Perforation rates are inversely related to age:

• about 80 to 100% in children under 3 years
• 50 to 70% in 3 to 5 years
• 30 to 40% in children aged 5 to 12 years
• about 20 to 30% in adolescents

Delay in diagnosis is the main contributor, because young children cannot give a history, and the omentum is underdeveloped, so the infection is poorly contained and the inflammation spreads quickly.

Pathophysiology is the same as in adults (lumen obstruction by faecolith or lymphoid hyperplasia). Important differences in children: more frequent diagnostic delay, more atypical presentations, greater perforation rate, and more frequent unnecessary surgery, so decisions benefit from structured scores and ultrasound.

Differential diagnosis: viral gastroenteritis, mesenteric adenitis, constipation, urinary tract infection, lower lobe pneumonia, streptococcal pharyngitis, intussusception, Meckel diverticulitis, Crohn disease, Henoch-Schonlein purpura, ovarian torsion or cyst, pelvic inflammatory disease, ectopic pregnancy, testicular torsion, diabetic ketoacidosis, sickle cell crisis, and abdominal migraine.

• Older children and adolescents have the classic sequence: periumbilical pain migrating to the right iliac fossa, anorexia, nausea, vomiting (after the pain began; if vomiting precedes the pain, gastroenteritis is more likely), and low grade fever. They may refuse to walk, walk bent over, or limp, and hopping and coughing hurt. Right iliac fossa tenderness, guarding, rebound, and Rovsing sign are present.
• Preschool children and infants: irritability, vomiting, fever, diarrhoea (30% have diarrhoea, causing diagnostic confusion with gastroenteritis), abdominal distension, lethargy, refusal to eat, and a limp or refusal to move the right leg. Perforation is often present at diagnosis (the child is toxic, with a rigid distended abdomen).
• Features of perforation: high fever (above 38.5 degrees C), persistent vomiting, tachycardia, diffuse tenderness and guarding, rigidity, distension, and shock. A mass in the right iliac fossa after 3 to 5 days indicates a phlegmon or abscess. Pelvic abscess may cause diarrhoea and tenesmus.
• Examination technique in children: build trust, examine with a warm hand and a distracting conversation, start away from the tender point, watch the face for grimacing, ask the child to jump or cough, and use a stethoscope to palpate. Digital rectal examination is not routine and should be reserved for equivocal cases.

Clinical scores:

• Paediatric Appendicitis Score (PAS): migration of pain, anorexia, nausea and vomiting, tenderness in the right iliac fossa (2 points), cough or hopping tenderness (2 points), fever, leucocytosis (2 points), and neutrophilia; total 10. A score of 7 or above suggests appendicitis; 3 or below is low risk
• Alvarado score and paediatric appendicitis risk calculator (pARC): validated tools combined with imaging and serial examination

Laboratory tests: full blood count (leucocytosis in most, but a normal count does not exclude), C-reactive protein (higher values correlate with perforation), urinalysis (excludes urinary tract infection, but sterile pyuria can occur), electrolytes, and a pregnancy test in post-menarchal girls. Procalcitonin is of limited use.

Imaging:

• Ultrasound is the first line investigation: non-compressible, blind ending tubular structure over 6 mm in outer diameter, wall thickness over 2 mm, hyperaemia on Doppler, appendicolith, periappendiceal fluid, and echogenic mesenteric fat. Sensitivity is about 85 to 95% and specificity about 90 to 95% in experienced hands. A normal appendix visualised clearly excludes it; if the appendix is not visualised and there is no secondary signs (non-visualisation), the risk is low in a child with low-to-moderate clinical risk, and a repeat examination or follow up is recommended
• MRI (rapid protocol without contrast, 5 to 10 minutes) is highly accurate (sensitivity 95% and specificity 97%) and avoids radiation; used after equivocal ultrasound where available
• CT with intravenous contrast is reserved for equivocal cases after ultrasound (and MRI if available), because of radiation concerns; use low dose protocols
• Algorithm: low risk (PAS under 4 and low pARC) observed; intermediate risk gets ultrasound, and if inconclusive MRI or CT, or serial examination; high risk goes to surgery without delay, with or without imaging

Initial care. Resuscitate and correct dehydration with isotonic fluid boluses of 10 to 20 mL/kg, followed by maintenance fluids with dextrose saline; nil by mouth; analgesia (paracetamol 15 mg/kg IV, ibuprofen 10 mg/kg, morphine 0.05 to 0.1 mg/kg IV titrated); antiemetic (ondansetron 0.1 to 0.15 mg/kg, maximum 4 mg). Early paediatric surgical consultation.

Antibiotics.

• Pre-operative: single dose prophylaxis for uncomplicated appendicitis, for example ceftriaxone 50 mg/kg (maximum 2 g) with metronidazole 10 mg/kg (maximum 500 mg) or cefoxitin 40 mg/kg; stop after surgery in simple appendicitis
• Complicated appendicitis (perforated, gangrenous, abscess): ceftriaxone 50 to 75 mg/kg daily with metronidazole 10 mg/kg every 8 hours, or piperacillin tazobactam 100 mg/kg of piperacillin component every 8 hours (maximum 4.5 g per dose; 90 to 112.5 mg/kg per dose depending on formulary), or meropenem 20 mg/kg every 8 hours for severe disease; continue until clinical resolution (afebrile for 24 hours, normalising white cell count, and tolerating diet) with a typical duration of 3 to 5 days post-operatively (4 days after source control is as effective as longer courses, and no oral step down is routinely necessary); consider switching to oral amoxicillin clavulanate 22.5 mg/kg of the amoxicillin component twice daily if early discharge is desired and the clinical picture permits