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Despite wide spread availability of sophisticated diagnostic imaging, acute appendicitis in pre-school children remains a diagnostic challenge. Most of these children present late, often with complications e.g. appendicular perforation, abscess formation and peritonitis and as result hospital stay is prolonged and is associated with increased morbidity and mortality.
The purpose of this article is to review peculiar features of acute appendicitis in preschool children.
Acute appendicitis is common surgical emergency among children (1–2% in pediatrics surgical admissions) [1–3]. Overall, 1–8% of children presenting with abdominal pain have acute appendicitis . However, Appendicitis is uncommon in pre-school Children (2 to 9% children presenting with acute appendicitis) . Despite the availability of advanced diagnostic imaging, the diagnosis of acute appendicitis in young children remains a challenge as most of such patients present late with complications e.g. perforation leading to abscess formation, generalized peritonitis and sepsis. The delay in the diagnosis of acute appendicitis has been attributed to nonspecific presentations, overlap of symptoms with many other common childhood illnesses, together with inability child to express and difficult abdominal examination in this age group. Misdiagnosis rate ranges from 28 to 57% in 2 to 12 year old children and approaches to nearly 100% in children younger than 2 years [6–8].
The vermiform appendix is a tube like diverticulum of the cecum with an average length of 4.5 cm in neonates and 9.5 cm in adults . The base is wider and funnel shaped in neonates and infants with lesser chances of luminal obstruction. It takes the cylindrical adult shape at the age of 1 to 2 years.
The base of the vermiform appendix is less likely to be variable in position and lies on the posteromedial surface of the cecum at the convergence of its three taenia coli, while its tip is highly variable in position. The appendicular tip is retrocaecal in 28–68%, followed by pelvic position in 27–53%, subcaecal in 2%, anterior or preilleal in 1%, within hernial sac in 2%, right upper quadrant in 4%, and in left upper and left lower quadrants in less than 0.1% each .
Fetal and infantile appendices are generally freely mobile and less likely to be fixed with the cecum, ascending colon, to the posterior abdominal wall and there are greater chances of diffuse spillage of intestinal contents after the appendix perforates in such patients, compared to a localized abscess in elderly children. The variable tip and different positions of the vermiform appendix might explain the nonspecific presentations of acute appendicitis, e.g. In retrocaecal and sub serosal positions if the appendix gets inflamed the anterior abdominal pain and tenderness are less likely to develop. However, these patients usually experience more flank pain or back pain with longer duration of symptoms and with higher rates of perforation.
The exact pathogenesis of acute appendicitis is multi factorial although it is still unclear. But it is irrefutable that obstruction of the lumen is the usually present. In preschool children this obstruction is usually due to lymphoid hyperplasia and less likely due to fecolith, as the appendix contains an excessive amount of lymphoid tissue in the submucosa which increase in size and number with growing age, reaching maximum in number and size during teenage with a higher possibility of developing acute appendicitis [1, 4]. Lymphoid hyperplasia is also associated with various inflammatory and infectious disorders such as gastroenteritis, amebiasis, respiratory infection, measles, and infectious mononucleosis. Faecoliths are formed by over layering of calcium salts and fecal debris on the inspissated feces within the lumen of the vermiform appendix. Luminal obstruction with continuous secretion and stagnation of fluids and mucus from epithelial cells result in increased intra-luminal pressure and distension of the appendix. Intestinal bacteria within the appendix multiply, and the edematous wall precipitates bacterial invasion. Also, the resulting compromise of the blood supply, decreased venous return, and eventually thrombosis of the appendicular artery and vein aggravates the inflammatory process, resulting in ischemia, necrosis, gangrene, and perforation.
The perforation of appendix result in either diffuse peritonitis, or localized appendicular abscess. Diffuse peritonitis is more common in younger children, due to a less developed omentum, whereas elderly children are relatively protected by well-developed omentum. The most common aerobic offenders for causing acute appendicitis are Escherichia coli, Klebsiella pneumoniae , peptostreptococcus, and pseudomonas species, and Bacteroides fragilis.
Acute appendicitis is one of the common causes of abdominal pain in children. The lifetime risk of developing acute appendicitis among males and females is 8.6 and 6.7%, respectively . Although acute appendicitis is uncommon in infants and younger children, still neonatal as well as prenatal cases have been reported [10–18]. The incidence of acute appendicitis gradually increases after birth, peaks during the late teens and gradually declines in the geriatric age. Recently published studies have revealed that the incidence of acute appendicitis varies considerably according to sex, race, socioeconomic and immigrant status of the general population [19–22]. Its incidence has been reported to be declining in some western countries during recent years [23, 24]. During the late half of the 20th century, the incidence of appendectomy has been declining among children of various age groups. The incidence of acute appendicitis has declined from 3.6/10,000 to 1.1/10,000 among preschoolers, from 18.6/10,000 to 6.8/10,000 in children aged 5–9 years, and from 29.2/10,000 to 19.3/10,000 in children aged 10–14 years . The decreasing incidence rates of acute appendicitis has been largely attributed to a better attention to various suggested etiological factors such as hygiene , diet , seasonal variation [28, 29], infection [4, 30], breast feeding  and genetic [32–34].
During early childhood, presentation is atypical which makes the diagnosis more difficult. Moreover, the children of this age group have poor communication skills that can results in miss understanding of the disease process. The varied clinical presentation in different age groups is well explained by anatomical variation and pathophysiological differences responsible for acute appendicitis. These factors are of great concern to the clinicians and emphasize the need to properly investigating such patients in achieving a successful management protocol.
In this age group, premature neonates are most likely to develop acute appendicitis [17, 35]. Here, luminal obstruction is not responsible for acute appendicitis. However, ischemia due to emboli or thrombotic event, obstructed internal or external hernia, cardiac anomalies and distal colonic obstruction as in Hirschprung’s disease, are the more likely causes of neonatal acute appendicitis.
Pain and nausea cannot be well appreciated as an evidence of acute appendicitis in these neonates. These patients usually present with abdominal distension in 60% to 90%, vomiting 59%, palpable mass 20–40%, irritability or lethargy in 22% and 12–16% with cellulitis of abdominal wall. However, hypotension, hypothermia, right hip stiffness and respiratory distress have been observed in some cases as well [12, 36–39].
The prominent symptoms in this age group are vomiting (85% to 90%), pain (35 to 81%), fever (40–60%), and diarrhea (18 to 46%). Other common symptoms during this age group are irritability (35% to 40%), cough or rhinitis (40%), grunting respiration (8% to 23%), right hip mobility restriction, pain and limping in 3% to 23%. Vomiting and irritability are also presenting symptoms of many other disorders at this age like gastroenteritis, mesenteric adenitis, intussusception, otitis media, and upper respiratory tract infections. On physical examination, majority of the infants (87% to100%) have temperature higher than 37oc and diffuse abdominal tenderness (55% to 92%); whereas localized right lower quadrant tenderness is observed in less than 50% of cases. Other noticeable signs are lethargy (40%), abdominal distension (30–52%), rigidity (23%), and abdominal or rectal mass (30%) [40–42]. As the presentation of acute appendicitis in this age group is nonspecific, vague, the mean time interval between the onsets of symptoms and final diagnosis is usually 3 to 4 days. This delay in diagnosis most often results in perforation (82–92%), and bowel obstruction 82% [40–42].
Acute appendicitis is still rare up to 6 years of age, accounting for only less than 5% of all childhood appendicitis [4, 43]. With growing age, children are able to communicate well and can describe the symptoms of acute appendicitis, early diagnosis of acute appendicitis becomes more easy and accurate. The majority of children in this age group present with complex complaints of 2 days duration and up to 17% have the symptoms for more than 6 days before the final diagnosis is reached . In this age group, abdominal pain is the most common presenting symptom (89% to100%), followed by vomiting (66% to100%), fever (80% to 87%) and anorexia (53% to 60%). On examination, localized right lower quadrant tenderness (58% to 85%) predominates over the diffuse tenderness (19% to 28%). Other physical signs include involuntary guarding (85%), rebound tenderness (50%), and temperature greater than 37.5 o c (82%) .
The non-specific clinical presentation in children less than 5 years, as well as difficult communicate with them , inadequate physical examination, irritability, and overlap of symptoms with other common childhood illnesses attribute to delayed diagnosis of acute appendicitis and high misdiagnosis rate. Hence they are more likely to develop complications such as perforation and abscess formation other factors contribute to perforation are thin-walled appendix, and inadequate omental barrier. The differential diagnosis in these children include, but not limited to, acute gastroenteritis, upper and lower respiratory tract infections, urinary tract infections, cholecystitis, constipation, intussusception , pelvic inflammatory disease, blunt abdominal trauma, obstructed hernia, testicular torsion, orchitis, nephrolithiasis, right hip septic arthritis, dehydration, sepsis, encephalopathy, and meningitis.
The overall rate of missed diagnosis ranges from 70 to100% among children of 3 years and younger, 19 to 57% in preschool age group (with perforation in 43% to 72% of the cases). This rate decreases to 12 to 28% for school age children, reaching less than 15% in adolescents [6, 43, 44].
In a clinical study, up to 15% of patients were seen twice or more in the emergency department before the diagnosis of acute appendicitis was made and the common features for misdiagnosed patients were relatively short duration of symptoms at the initial visit, most of them attended late at night, had fewer physical findings on examination, and were not well investigated . The rate of misdiagnosis rises as age decreases, and young children have a 5-fold risk of complicated appendicitis . In a study on 102 children where investigators explored risk factors for appendicular perforation, it was found that the duration of pain and the presence of appendicolith were the most statistically significant factors .
The diagnosis of acute appendicitis is not easy in young children. It necessitates the need for certain laboratory and radiological investigations in all age groups for making an accurate diagnosis,:
Children diagnosed with acute appendicitis should be immediately admitted for observation and/or emergent appendectomy. Children with atypical presentation require surgical consultation. A protocol using the appropriate application of scoring system, radiological adjuncts and in-patient close clinical observation will help to diagnose or exclude acute appendicitis. In-patient observation by a surgeon can help in differentiating atypical presentation of acute appendicitis from other disorders. A group of patients with very low risk based on the Alvorado or PAS scoring system can be discharged from the emergency room with an advice of repeat evaluation after 8 to 12 h [107, 108].
A protocol of active monitoring that involves frequent clinical examinations every 4 to 6 h, with or without repeat ultrasound, for patients without evidence of obvious physical signs mandating surgical exploration (ie, the presence of rebound tenderness or peritonitis) will enhance the diagnostic yield and will decrease the utilization of CT scan and radiation risk [3, 109].
Historically, open appendectomy has been practiced in young children all over the world for acute appendicitis. However with the advent of minimally invasive techniques, laparoscopic appendectomy has become increasingly popular among pediatric surgeons. Recently, researchers have started the use of antibiotics alone to treat low grade appendicitis as an alternative to surgery when the family refuses or prefers to avoid surgery . Traditionally, appendicular mass in very young age group has been managed as in adult population by conservative management, followed by interval appendectomy with good outcome, although this group of children poorly respond to conservative management. It is widely accepted that patients with appendicular abscess can be managed with immediate CT scan, or ultrasound guided per-cutaneous drainage and parenteral broad spectrum antibiotics, followed by interval appendectomy [111, 112]. The patients can later get the benefits of minimally invasive approach as well . In case of failed per-cutaneous drainage, open or laparoscopic surgical drainage is an alternative. However, we should bear in mind that young children don’t form localized abscess as older children and early intervention is recommend in such patients. Both mortality and morbidity rates in acute appendicitis have been significantly reduced with early diagnosis, broad spectrum antibiotics, fluid resuscitation, better anesthesia, well equipped intensive care units and improved surgical skills [114, 115].
Acute appendicitis in young children of preschool age group and infants is uncommon. Delay in the diagnosis and management predominantly result from poor communication skill, failure to elicit physical signs in irritable children, atypical presentation, and overlap of symptoms with other disorders. Late presentation leads to onset of complications such as appendicular perforation and peritonitis. Diagnosis in this age group requires a high index of suspicion, a careful history, and serial physical examinations. Admit and observe policy is highly recommended in equivocal cases. Diagnostic accuracy can be enhanced with the appropriate use of imaging tools such as ultrasound and CT scan depending upon the available facilities. Early diagnosis and prompt surgical intervention can reduce the morbidity and mortality rates associated with complicated appendicitis.
The author declares that he has no competing interests.