Acute appendicitis is a common cause of acute abdominal pain in children. In general, the condition tends to present more severely in children than in adults, making timely diagnosis and appropriate treatment critically important. Acute appendicitis in children is most frequently observed in those aged 6–12 years, with a slightly higher incidence in males compared to females. The incidence increases with age after 5 years, but cases are rare in children under 2 years of age. In younger children, symptoms are often atypical, and their underdeveloped omentum limits the ability to localize inflammation. This results in a higher risk of rapid disease progression, including suppuration, perforation, necrosis, and diffuse peritonitis in a short time. Delayed diagnosis and treatment can lead to severe complications, or even death, warranting close attention. The misdiagnosis rate for acute appendicitis in infants and young children is estimated to be between 35% and 50%, and it exceeds 90% in neonates.
Etiology
The causes of acute appendicitis in children are complex and are associated with several factors:
Appendiceal Obstruction
Retained secretions increase intraluminal pressure, leading to impaired blood flow in the appendiceal wall and susceptibility to bacterial invasion. Common causes of obstruction include fecaliths, foreign bodies (e.g., fruit pits, ascaris parasites), appendiceal torsion, and luminal scarring or strictures.
Bacterial Infection
Bacteria can reach the appendix through damaged mucosa or via the bloodstream, triggering acute inflammation, which may be associated with conditions like pharyngitis, upper respiratory infections, or tonsillitis.
Neural Reflex
Gastrointestinal dysfunction may induce reflexive spasms of the appendiceal muscles and blood vessels, leading to luminal obstruction and impaired blood flow, which contribute to inflammation.
Pathology
Based on the pathological progression, acute appendicitis can be classified into three types:
Uncomplicated Appendicitis
The primary pathological changes involve mucosal hyperemia and edema, with infiltration by polymorphonuclear neutrophils.
Suppurative Appendicitis
In addition to mucosal involvement, the muscular and serosal layers are affected. Purulent exudates are present, and early peritoneal infection with exudation may occur, which can progress to perforation.
Gangrenous Appendicitis
Infection rapidly causes vascular spasm and thrombosis, leading to impaired blood circulation and extensive necrosis of the appendiceal wall, which appears dark purple. Although exudation may be limited, rapid infiltration of surrounding tissues often occurs, increasing the likelihood of adhesions.
Uncomplicated appendicitis is limited to the mucosa and may resolve with conservative treatment. However, secondary infection due to poor drainage of the appendiceal lumen may cause progression to suppurative appendicitis. Younger children, with shorter omenta and thinner appendiceal walls, are more prone to perforation and have less ability to localize inflammation, increasing the risk of diffuse peritonitis. Additionally, in children, the cecum is situated higher and is relatively mobile, leading to variability in tenderness location, which may manifest in atypical areas such as the right mid-abdomen or below the umbilicus.
Clinical Manifestations
Abdominal Pain
Abdominal pain is the primary symptom of acute appendicitis in children. The typical progression starts with pain around the periumbilical or epigastric region, which moves to the right lower abdomen after a few hours. The pain is continuous, but in cases of obstructive appendicitis, it may involve severe intermittent colicky pain. If perforation occurs, diffuse peritonitis causes persistent pain throughout the abdomen.
Gastrointestinal Symptoms
Affected children may exhibit poor appetite. In the early stages, nausea and vomiting may occur, though vomiting is typically infrequent. Reflexive vomiting is seen in the initial stages, while frequent vomiting and abdominal distension are more common after perforation and diffuse peritonitis develop. Constipation is often noted, but concurrent peritonitis or pelvic abscess may lead to rectal irritation, causing frequent watery stools.
Fever and Tachycardia
A slight fever is common in the early stages, but as the disease progresses, temperatures can rapidly rise to 38–39°C or higher. The speed of temperature elevation is more pronounced in younger children. Heart rate increases proportionally with fever and worsening intoxication. Severe cases present with high fever, rapid but weak pulse, and signs of systemic toxicity.
Abdominal Signs
Abdominal signs provide the most diagnostic value. Repeated examinations and thorough comparison of the left, right, upper, and lower abdominal areas are often necessary, especially in younger or uncooperative children. Sedatives may occasionally be required, and assessment during sleep may reduce the likelihood of misdiagnosis.
Fixed tenderness in the right lower abdomen is the most reliable sign. Early cases typically do not involve muscle rigidity, but localized muscular tension appears when inflammation spreads to the retroperitoneum. The anatomical position of the appendix may vary and does not always correspond to McBurney’s point. Tenderness may occur near the umbilicus or behind the cecum, but the location of tenderness generally remains consistent in individual patients.
When perforation is complicated by diffuse peritonitis, symptoms of toxicity become severe and often include lethargy, high fever, dehydration, and abdominal distension. Physical examination reveals weakened or absent bowel sounds, generalized abdominal tenderness, muscle rigidity, and the characteristic "board-like abdomen," with the most pronounced severity in the right lower quadrant.
Rectal examination can provide diagnostic value. Tenderness and swelling may be palpable on the anterior right wall of the rectum in appendicitis, and localized abscess formation may present as a palpable mass. In smaller children, a swollen appendix may even be directly palpable.
Auxiliary Examinations
Laboratory Tests
White blood cell count can be significantly elevated, typically ranging from (15–20) × 109/L in the early stages, with neutrophils comprising 80–90% of the total count. In rare cases of severe shock or systemic toxicity, body temperature and white blood cell count may appear normal or slightly reduced, reflecting an impaired immune response.
Ultrasound (B-Scan Ultrasound)
Ultrasound is currently the most commonly used auxiliary diagnostic tool. Findings include an inflamed, swollen appendix with a diameter greater than 6 mm, thickened walls, and the presence of intraluminal fluid, pus, or fecaliths. Adhesions with surrounding intestinal loops, localized abscess formation, or other complications may also be identified.
Abdominal Puncture
Abdominal puncture may be considered for challenging cases to assist in diagnosis.
CT or MRI
CT or MRI is typically reserved for cases with diagnostic uncertainty or when rare conditions such as tumors are being considered.
Diagnosis and Differential Diagnosis
Acute appendicitis can often be diagnosed based on a history of classic migratory right lower abdominal pain and the presence of fixed tenderness in the right lower quadrant, supported by laboratory and ultrasound findings. However, some cases present atypically with variable symptoms, particularly in children, who may have difficulty articulating a clear history and often fear physical examination. Misdiagnosis with other acute abdominal conditions is not uncommon. Common differential diagnoses include the following:
Acute Mesenteric Lymphadenitis
This is often associated with a recent history of acute upper respiratory tract infections or acute tonsillitis. The abdominal pain is more generalized, but since mesenteric lymph nodes are concentrated near the terminal ileum, right lower abdominal pain may be more prominent. Tenderness is usually not well-localized, and there is no muscle rigidity. Observation for several hours often shows no progression or a reduction in symptoms.
Acute Gastroenteritis
Some children with enteritis may initially present with abdominal pain, vomiting, and fever before diarrhea develops, leading to potential misdiagnosis as appendicitis. The abdominal pain is typically colicky and intermittent, with tenderness that is not fixed and minimal muscle rigidity. Observation over several hours often reveals the onset of diarrhea and resolution of tenderness, confirming the diagnosis.
Meckel's Diverticulitis
The diverticulum is located in the terminal ileum approximately 20–100 cm from the ileocecal valve. Inflammation leads to tenderness and muscle rigidity close to the midline, presenting symptoms similar to those of suppurative or gangrenous appendicitis, making preoperative differentiation difficult. A history of rectal bleeding should raise suspicion. Both conditions require early surgical intervention. During appendectomy, if the appendix appears normal, the terminal ileum within 100 cm of the ileocecal valve should be inspected for Meckel's diverticulum.
Henoch-Schönlein Purpura
Intraperitoneal and subserosal hemorrhage can cause abdominal pain and tenderness without muscle rigidity. The presence of subcutaneous purpura, joint swelling, and joint pain aids differentiation.
Right-Sided Pneumonia or Pleuritis
The phrenic nerve shares its origin with abdominal wall sensory nerves from the T7–T12 spinal segments. In cases of lower lobe right-sided pneumonia or pleuritis, diaphragmatic irritation may lead to referred abdominal pain and muscle tension in the right abdomen. Protecting the chest by pressing the right costal margin while gradually compressing the right lower abdomen can reveal that muscle tension diminishes progressively. In addition, pneumonia often presents with tachypnea and nasal flaring. Chest auscultation may reveal friction rubs, crackles, or diminished breath sounds, with chest X-rays providing further diagnostic confirmation.
Intestinal Spasms
School-aged children may experience recurrent episodes of intestinal spasms lasting 10–20 minutes. During episodes, tenderness is not fixed, there is no muscle rigidity, and symptoms generally resolve spontaneously without the need for specific treatment.
Torsion of an Ovarian Cyst
Girls experiencing torsion of a right-sided ovarian cyst may present with severe intermittent colicky pain in the right lower abdomen. Muscle tension and tenderness may develop due to hemorrhage or necrosis caused by compromised blood flow. Palpation of a round pelvic mass during a rectal or bimanual pelvic examination confirms the diagnosis. Ultrasound is useful for further differentiation.
Primary Peritonitis
More common in girls, this condition has an acute onset with high fever, abdominal distension, vomiting, elevated white blood cell counts (20–30) × 109/L, and diffuse abdominal tenderness and rigidity, especially in the lower abdomen. Differentiating it from peritonitis caused by perforated suppurative appendicitis can be challenging. Purulent fluid obtained via abdominal puncture is thin and odorless, with microscopy revealing cocci, confirming primary peritonitis. Exploratory laparotomy may sometimes be necessary to establish the underlying cause.
Ileocecal Tuberculosis
This may be misdiagnosed as gangrenous appendicitis with infiltration or abscess formation. Affected children often have a history of chronic abdominal pain, progressive weight loss, frequent low-grade fevers, and palpable masses. Other sites of tuberculosis involvement should also be examined. Tuberculosis tests and further observation are needed for a definitive diagnosis.
Acute Necrotizing Enterocolitis
This presents with a history of diarrhea and bloody stool, high fever, signs of severe infection or shock, and tenderness with rigidity in the right lower or entire abdomen. Differentiating between necrotizing enterocolitis and peritonitis caused by appendicitis often requires exploratory laparotomy for definitive diagnosis and appropriate surgical treatment.
Treatment
The primary principle for managing acute appendicitis in children is early surgery. Surgical options include open appendectomy or laparoscopic appendectomy. For cases with a prolonged disease course (three or more days) and inflammatory masses in the right lower abdomen suggesting an appendiceal abscess, nonoperative management may be attempted with careful observation. Indicators for transitioning to surgery include rising temperatures, expanding regions of tenderness, or increased tension in the abscess. Patients with uncertain diagnoses or suspected appendicitis warrant surgical exploration to rule out emergency conditions.
Given that the appendix serves as a microbial reservoir supporting gut flora restoration after gastrointestinal infections, emerging treatments like Endoscopic Retrograde Appendicitis Therapy (ERAT) have been explored. ERAT involves endoscopic approaches for flushing the appendix, removing fecaliths, and placing drainage stents. Clinical success has been achieved in certain cases, but long-term outcomes require further investigation.