Pediatric Appendicitis

Etiology

Appendicitis most commonly results from obstruction of the appendiceal lumen, which may be caused by lymphoid hyperplasia, fecaliths, foreign bodies, or, less commonly, tumors.[4][5] The appendix contains abundant lymphoid tissue in the mucosa and submucosa, especially in children and adolescents, making it particularly susceptible to lymphoid hyperplasia. This immune response can narrow or occlude the lumen, leading to increased intraluminal pressure, bacterial overgrowth, ischemia, and subsequent inflammation of the appendiceal wall.

Epidemiology

Appendicitis is the most common surgical condition in children, with an annual incidence in the United States estimated at 83 cases per 100,000 population.[6] Although it can occur at any age, the peak incidence is between 15 and 19 years.[7] Appendicitis is slightly more common in males than females, with a male-to-female ratio of approximately 1.4:1. The lifetime risk is about 8.6% in males and 6.7% in females.[8]

Globally, incidence rates vary based on geographic and socioeconomic factors, with higher rates observed in industrialized countries. Improved sanitation and dietary changes have been associated with declining incidence in some regions, while increasing rates are noted in others undergoing dietary Westernization.

Children have a higher risk of perforation compared to adults, with perforation occurring in approximately 30% of pediatric hospital admissions for appendicitis.[9] This may be due to nonspecific presentations that mimic other gastrointestinal illnesses, contributing to delays in diagnosis and treatment.[10]

Pathophysiology

Appendicitis typically begins with luminal obstruction, which leads to continued mucus secretion, increased intraluminal pressure, and progressive distention of the appendix. As pressure builds, venous outflow is compromised, resulting in ischemia, bacterial overgrowth, and eventual necrosis.[11] If untreated, this process culminates in perforation and peritonitis.[12] Pain initially presents as poorly localized periumbilical discomfort due to visceral afferent fibers that follow sympathetic innervation and enter the spinal cord at T10. The pain localizes to the right lower quadrant as inflammation progresses and involves the parietal peritoneum.

History and Physical

Clinical History

The classic presentation of appendicitis begins with vague, colicky periumbilical or epigastric pain that migrates to the right lower quadrant within 24 hours of symptom onset. Abdominal pain often precedes vomiting and may be accompanied by anorexia and fever. Dysuria or hematuria can occur due to the appendix’s proximity to the urinary tract. Anorexia is common, but not universally present. Diarrhea may also be present and can lead to misdiagnosis as gastroenteritis, particularly in younger children.

Typical symptoms are often absent in the pediatric population, especially in children younger than 5. History may include nonspecific complaints eg, diffuse abdominal pain, vomiting, low-grade fever, or irritability in these cases. Signs (eg, lethargy, fever, or diffuse tenderness) may be the only clues in infants and toddlers.

The following anatomic positions of the appendix significantly influence symptom location:

• A retrocecal appendix can present with flank or back pain.
• A pelvic appendix can present with suprapubic pain, urinary symptoms, or tenesmus.
• A long appendix can present as right upper quadrant or left lower quadrant pain.[13][14]

Physical Examination

Physical findings of pediatric appendicitis vary by age including:

• Age <2 years: Nonspecific signs, eg, fever and diffuse abdominal tenderness
• Ages 2 to 5 years: Fever, right lower quadrant tenderness, and involuntary guarding
• Age >5 years: Localized lower quadrant tenderness, guarding, and rebound [15]

The most consistent finding is tenderness at McBurney’s point—two-thirds the distance from the umbilicus to the right anterior superior iliac spine. Other exam signs include:

• Rovsing sign: Right lower quadrant (RLQ) pain with palpation of the left lower quadrant.

• Psoas sign: RLQ pain with passive extension of the right thigh.

• Obturator sign: RLQ pain with internal rotation of the flexed right hip.

Clinicians should note that no single historical or physical exam finding is diagnostic. These signs should be interpreted in the context of the overall clinical picture. A rectal examination is generally not helpful in evaluating pediatric appendicitis.

Evaluation

Appendicitis remains a clinical diagnosis, and imaging is not always required when the presentation is classic. In cases with atypical symptoms, particularly in female patients of reproductive age, imaging is useful to improve diagnostic confidence. Surgical consultation should be sought early, especially in patients with clear signs of appendicitis, and should not be delayed for imaging or laboratory studies. Laboratory and imaging tests should be interpreted in the context of the patient's clinical history and physical examination.[3][16][17] 

White Blood Cell Count

Although no definitive biomarker for appendicitis has been established, laboratory tests can support clinical suspicion. Leukocytosis with a left shift may suggest early inflammation, but lacks specificity. Elevated white blood cell (WBC) count can also be seen in gastroenteritis, mesenteric adenitis, and pelvic inflammatory disease, while a normal WBC count does not exclude appendicitis.

Urinalysis

Urinalysis is typically normal but may show pyuria in 7% to 25% of pediatric cases.[18] This finding may be due to an inflamed appendix irritating the adjacent ureter or bladder.

Ultrasound

Ultrasound (US) is the preferred initial imaging modality in children due to its safety profile and absence of ionizing radiation. Ultrasound is also cost-effective, though operator-dependent. A noncompressible, enlarged appendix (>6 mm) with wall thickening and luminal distention is considered diagnostic. Other findings may include an appendicolith, periappendiceal fluid, or a complex RLQ mass. Sensitivity ranges from 72.5% to 94.8%, and specificity from 95% to 99%. Further imaging with computed tomography (CT) or magnetic resonance imaging (MRI) may be required when the US is nondiagnostic. A positive ultrasound may obviate the need for CT, while a negative or inconclusive result does not reliably exclude appendicitis.[19][20]

Computed Tomography Scan

Abdominal and pelvic CT offers high diagnostic accuracy, with a sensitivity of 94% and specificity of 95%.[21] This modality remains the most definitive, especially in equivocal or complicated cases. However, its use should be judicious due to concerns about radiation exposure in children.[22] To address this, limited-range CT protocols have been proposed to significantly reduce radiation dose while maintaining diagnostic quality.[23]

Characteristic CT findings in appendicitis include:

• A dilated appendix (>6 mm)
• Wall thickening (>2 mm)
• Peri-appendiceal fat stranding
• Appendicolith
• Abscess
• Free intraperitoneal fluid

In cases with prolonged symptoms or diffuse peritoneal signs suggestive of rupture, CT remains the preferred modality. However, perforation can obscure hallmark features, sometimes making the appendix itself difficult to visualize.

Magnetic Resonance Imaging

MRI is a reliable diagnostic tool for appendicitis and is especially useful when ultrasound is inconclusive. It offers comparable sensitivity and specificity to CT, without the risks of ionizing radiation.[24][25] However, MRI has practical limitations, including higher cost, longer scan times, and the need for skilled interpretation. Availability is often limited, and younger children may require sedation.

MRI is not the preferred modality for unstable patients. Intravenous (IV) gadolinium contrast should be avoided during pregnancy due to placental diffusion, as well as in patients with renal impairment, due to the risk of nephrogenic systemic fibrosis. Recent studies have evaluated the effectiveness of rapid, noncontrast MRI protocols that do not require sedation, expanding MRI's potential use in pediatric populations.[26]

Clinical Decision Tools for Pediatric Appendicitis

Several clinical scoring systems have been developed to assist in the risk stratification of pediatric patients with suspected appendicitis. These tools integrate clinical findings and laboratory values to categorize patients into low, moderate, or high-risk groups. When used with ultrasonography, they improve diagnostic accuracy and help reduce unnecessary CT imaging.[27] Commonly used tools include the following:

• Alvarado score: A 10-point system based on the mnemonic MANTRELS: Migration of pain, Anorexia, Nausea/vomiting, Tenderness in the right lower quadrant, Rebound pain, Elevation in temperature, Leukocytosis, and Shift to the left. It was initially developed for adults but is also applied in pediatric populations.[28]

• Pediatric appendicitis score (PAS): This score considers migration of pain, anorexia, nausea or vomiting, fever >38 °C, RLQ tenderness, percussion or hopping tenderness, leukocytosis >10,000 cells/mm³, and polymorphonuclear neutrophilia >7,500 cells/mm³. A score of ≥6 is suggestive of appendicitis.[29]

• Pediatric appendicitis risk calculator (pARC): A more comprehensive tool, pARC incorporates age, sex, temperature, symptom duration, pain location and migration, nausea/vomiting, pain with walking, guarding, WBC, and absolute neutrophil count. With an ANC of 0.85, it demonstrates superior predictive accuracy compared to other scoring systems.[30]

Treatment / Management

Uncomplicated Appendicitis

Appendectomy remains the standard of care for acute, uncomplicated appendicitis, with laparoscopic appendectomy preferred due to faster recovery and fewer complications compared to open surgery.[31][32] However, recent evidence has challenged the universality of surgical management. Multiple randomized clinical trials in adults have shown that nonoperative treatment, primarily with antibiotics, can be safe and effective for select cases of uncomplicated appendicitis.[33][34] A systematic review of 8 randomized trials found no significant difference in outcomes between operative and nonoperative approaches. This has prompted interest in extending nonoperative strategies to pediatric populations.[35][36](A1)

Nonoperative management may be considered in carefully selected children to avoid surgery-related risks. Inclusion criteria typically include:

• Age >7 years

• White blood cell count between 5,000 and 18,000/μL

• Symptom duration <48 hours

• Imaging confirming nonperforated appendicitis

• Appendiceal diameter <1.1 cm

• Absence of appendicolith, phlegmon, or abscess

Exclusion criteria are based on predictors of nonoperative failure, such as prolonged symptoms, presence of an appendicolith or abscess, and significantly elevated inflammatory markers (eg, CRP >4 mg/dL).

The nonoperative protocol generally includes 1 to 2 days of intravenous broad-spectrum antibiotics, followed by a 7- to 10-day course of oral antibiotics if clinical improvement occurs. Children who fail to improve—marked by persistent pain, fever, or inability to tolerate a diet—should undergo prompt surgical intervention. While this approach may lead to more extended hospital stays and carries a risk of recurrence, careful patient selection can minimize these drawbacks.[37]

Complicated Appendicitis

Appendicitis is classified as complicated when there is gross perforation, presence of a fecalith, abscess, or frank purulence in the abdomen.[38] Management depends on clinical stability and the extent of infection, including:

• Generalized peritonitis: requires emergency appendectomy

• Contained perforation with abscess: may be managed with intravenous antibiotics alone or in combination with percutaneous drainage

• Interval appendectomy (performed weeks later): sometimes considered after nonoperative resolution of infection, though routine use remains debated

Current United States and international guidelines support a tailored approach, prioritizing early diagnosis, appropriate imaging, and timely surgical consultation, while allowing for selective nonoperative strategies in appropriate patients.

Differential Diagnosis

In children, abdominal pain can result from a wide range of conditions that may mimic acute appendicitis. Careful clinical evaluation is essential, especially in populations such as infants, sexually active adolescents, and those with atypical presentations, to rule out alternative diagnoses, including:

• Intussusception: Presents with intermittent, severe abdominal pain, a palpable abdominal mass, and “currant jelly” stools. This condition may be confused with appendicitis due to overlapping pain symptoms.

• Malrotation with volvulus: Often presents in infancy with bilious vomiting and abdominal distension. Pain may be severe and disproportionate to physical exam findings.

• Ectopic pregnancy: In adolescent females, this must be ruled out. Ectopic pregnancy typically presents with lower abdominal pain, amenorrhea, and possibly vaginal bleeding.

• Testicular torsion: Can present with abdominal pain and should always be considered in boys with scrotal discomfort, swelling, or tenderness. A genitourinary exam is critical to exclude this urologic emergency.

• Gastroenteritis: Viral or bacterial gastroenteritis can cause abdominal pain, vomiting, and diarrhea, overlapping with symptoms of appendicitis.

• Pelvic inflammatory disease (PID): This condition should be considered in sexually active adolescent females presenting with lower abdominal or pelvic pain. Diagnosis is clinical and supported by findings such as cervical motion tenderness, uterine tenderness, or adnexal tenderness on pelvic examination.

A thorough history, physical exam, and appropriate use of laboratory and imaging studies are essential to differentiate these conditions from appendicitis.

Prognosis

The prognosis for otherwise healthy children with uncomplicated appendicitis is generally excellent. Most recover fully after appendectomy, with a return to school expected within 1 week and resumption of full physical activity within 2 to 3 weeks, depending on the individual. Nonoperative management has shown promising results in select cases. However, studies report a recurrence rate of approximately 22% at 1 year and increased resource utilization, including more extended hospital stays and follow-up requirements.[39] In contrast, the prognosis worsens significantly with complicated appendicitis, eg, perforation or abscess formation, which is associated with increased morbidity and, in rare cases, mortality. Early recognition and appropriate intervention are key to minimizing complications and improving outcomes.

Complications

Perforation is a significant complication of appendicitis, with reported rates ranging from 10% to 30%, though this varies widely by age. Children at the extremes of age, particularly those under 2 years, are at the highest risk, with perforation rates reported as high as 90% in this group.[13] Patients with perforated appendicitis face a markedly increased risk of postoperative complications, which occur in approximately 20% to 30% of cases. These may include intra-abdominal abscess formation, diffuse peritonitis, and sepsis.

The most common postoperative complication following appendectomy is wound infection. Other complications, including postoperative intra-abdominal abscess and small bowel obstruction, occur more frequently in cases of complicated appendicitis. The incidence of these complications is approximately 6.7% in complicated appendicitis compared to 1.7% in uncomplicated cases.[40]