Acute appendicitis in children: Clinical manifestations and diagnosis

INTRODUCTION — 

This topic will discuss the epidemiology, clinical features, and evaluation of children with suspected appendicitis. Detailed discussions of diagnostic imaging and treatment for pediatric appendicitis are found elsewhere. (See "Acute appendicitis in children: Diagnostic imaging" and "Acute appendicitis in children: Management".)

ANATOMY — 

In the majority of normal children, the appendix is located in the right lower quadrant of the abdomen, where it arises from the posteromedial aspect of the cecum and inferior to ileocecal junction. The tip of the appendix has a variable location but is retrocecal in over 60 percent of patients [1]. It is typically 6 to 10 cm in length.

The appendix may lie in the upper abdomen or on the left side in children with congenital abnormalities of intestinal position such as malrotation, situs inversus totalis, or following repair of diaphragmatic hernia, gastroschisis, and omphalocele [2].

Some anatomic features of the appendix may play a role in the incidence and presentation of appendicitis throughout childhood. These include the following [3]:

●In the first year of life, the appendix is funnel-shaped, perhaps making it less likely to become obstructed. (See 'Neonatal appendicitis' below.)

●Lymphoid follicles (round collection of lymphocytes and reticular cells) are interspersed in the colonic epithelium that lines the appendix and may play a role in obstruction of the appendix since these follicles reach their maximal size during adolescence, the age group in which the peak incidence of appendicitis occurs.

●The omentum is very thin and underdeveloped in young children and often cannot successfully seal off an appendiceal perforation, which may account for the diffuse peritonitis that typically follows perforation in young children.

PATHOPHYSIOLOGY — 

Most commonly, appendicitis is caused by nonspecific obstruction of the appendiceal lumen [3,4]. Fecal material (usually referred to as a fecalith) is the most common culprit; undigested food or other foreign material may also be responsible. Less commonly, enteric pathogens may directly infect the appendix or cause localized appendiceal lymphoid hyperplasia with obstruction [5]. Specific organisms include:

●Adenovirus (in combination with intussusception) [6]

●Rubeola virus (measles) [7]

●Epstein-Barr virus [8]

●Actinomyces israeli (Actinomycosis) [9]

●Parasites such as Enterobius vermicularis (pinworms) [10] or Ascaris lumbricoides (roundworms) [11]

Rarely, pediatric appendicitis arises from other conditions such as:

●Crohn disease (granulomatous inflammation of the appendix) [12]

●Appendiceal carcinoid tumor [13]

●Burkitt lymphoma [14]

●Appendiceal duplication (often in association with other duplications of the gastrointestinal genitourinary tract in children) [15]

Inspissated mucous obstruction of the appendiceal lumen in children with cystic fibrosis may mimic appendicitis clinically and on imaging but is more commonly a manifestation of distal intestinal obstruction syndrome. (See "Cystic fibrosis: Overview of gastrointestinal disease", section on 'Appendiceal disease'.)

EPIDEMIOLOGY — 

Appendicitis is the most common indication for emergency abdominal surgery in childhood and is diagnosed in 1 to 8 percent of children evaluated urgently for abdominal pain [16,17]. In the United States, the incidence increases from an annual rate of one to six per 10,000 children between birth and four years of age to 19 to 28 per 10,000 children younger than 14 years [18-20]. It presents most frequently in the second decade of life. Fewer than 5 percent of patients diagnosed with appendicitis are five years of age or less [21]. Males are more commonly affected than females (lifetime risk 9 and 7 percent, respectively). In South Korea, the epidemiology of appendicitis is similar to the United States, with a higher incidence during the second decade of life but no sex-based differences in life time risk [22].

Advanced disease is common in children younger than five years of age, occurring in up to 57 percent of cases [23]. This finding is explained, at least in part, by the frequency of nonspecific symptoms in young children with appendicitis, which leads to a delay in the diagnosis. It is also likely that the disease progresses more rapidly to generalized peritonitis in young children because of their underdeveloped omentum. (See 'Anatomy' above and 'Young children (<5 years)' below.)

Traditionally, success in achieving the goal of timely and accurate diagnosis for appendicitis has been reflected, in part, by the balance between perforation rates and rates of negative appendectomy. In general, perforation correlates with duration of symptoms [24]. The reported rates of perforation vary significantly by age as follows:

●Neonates – 50 to 85 percent [25-28]  

●Young children (<5 years) – 51 to 100 percent [26,29-34]

●School-age (5 to 12 years) – 11 to 32 percent [31,33]

●Adolescents (>12 years) – 10 to 20 percent [18,23,35]

Similarly, negative appendectomy rates vary by age but are also impacted by sex. In 2023, the overall negative appendectomy in US children was 2.4 percent [36]. The highest rates are seen in children <5 years and girls old enough to experience ovarian pathologies [36,37].

CLINICAL MANIFESTATIONS

Common signs and symptoms — The classic presentation of appendicitis includes the following clinical findings, which usually occur in this order [3]:

●Anorexia

●Periumbilical pain (early)

●Vomiting after the onset of pain

●Migration of pain to the right lower quadrant

Additional clinical signs and symptoms include:

●Pain with movement – walking or shifting position in bed or on stretcher

●Fever (commonly occurring 24 to 48 hours after onset of symptoms)

●Right lower quadrant tenderness

●Signs of localized or generalized peritoneal irritation such as:

•Localized right lower quadrant abdominal tenderness elicited by cough, hopping, or the examiner bumping the examining table or the soles of the patient's feet.

•Involuntary muscle guarding with abdominal palpation.

•Positive Rovsing sign (pain in the right lower quadrant with palpation of the left side).

•Obturator sign (pain on flexion and internal rotation of the right hip, which is seen when the inflamed appendix lies in the pelvis and causes irritation of the obturator internus muscle).

•Iliopsoas sign (pain on extension of the right hip, which is found in retrocecal appendicitis).

•Rebound tenderness (elicited by the examiner placing steady pressure with his or her hand in the right lower quadrant for 10 to 15 seconds and then suddenly releasing the pressure; a positive finding consists of increased pain with removal of pressure). Percussion tenderness can also effectively reveal underlying peritonitis. It is elicited in a gentler manner compared with rebound tenderness by tapping or percussing over an area of tenderness. Should this very superficial stimulus produce pain, then the clinician should suspect peritonitis.

The Rovsing, obturator, and iliopsoas signs may be difficult to elicit in young children. In addition, as with adults, their accuracy has not been well defined [3,38]. The absence of the classic signs of appendicitis should not cause the clinician to exclude the diagnosis of appendicitis. However, when present in children 3 to 12 years of age, these signs have high specificity for acute appendicitis (86 to 98 percent, depending upon age) [31].

Although this classic pattern of clinical findings does occur in school-age children and adolescents, it is less common overall in pediatric patients with appendicitis than in adults. (See 'School-age (5 to 12 years)' below and 'Adolescent' below and "Acute appendicitis in adults: Clinical manifestations and differential diagnosis", section on 'Clinical manifestations'.)

In infants and young children, this pattern may not occur at all, perhaps because of differences in the pathophysiology of the disease and in the child's ability to relate information regarding signs and symptoms. (See 'Neonates (0 to 30 days)' below and 'Young children (<5 years)' below.)

Furthermore, among children, the absence of classic clinical features of appendicitis (such as fever, anorexia, migration of pain to the right lower quadrant, and rebound tenderness) are neither sensitive nor specific for excluding appendicitis, especially in younger patients [3]. This was demonstrated in a prospective series describing children evaluated in an emergency department (ED) for suspected appendicitis in whom the following features were noted among the patients with appendicitis [39]:

●Lack of migration of pain to right lower quadrant in 50 percent

●Absence of anorexia in 40 percent

●No rebound tenderness in 52 percent

Thus, diagnosing appendicitis among children is frequently challenging because typical symptoms and signs are often not present, specific findings of appendicitis are difficult to elicit in this patient population, and clinical findings frequently overlap with other conditions. (See 'Differential diagnosis' below.)

Clinical features by age

Neonates (0 to 30 days) — Case reports and case series indicate that abdominal distension, vomiting, and decreased feeding, are the most commonly reported findings in neonates with appendicitis [25,40]. Temperature instability/fever and septic shock may also develop. The approximate frequency of clinical features of neonatal appendicitis based upon over 100 cases is as follows [25,40]:

●Abdominal distension – 50 to 75 percent

●Vomiting (may be bilious) – up to 40 percent

●Decreased or refused oral intake – up to 40 percent

●Abdominal tenderness – 9 to 38 percent

●Sepsis – 38 percent

●Temperature instability – 33 percent

●Fever – 28 percent

●Lethargy – 18 to 24 percent

●Abdominal wall cellulitis – 4 to 24 percent

●Respiratory distress – 15 percent

●Abdominal mass – 3 to 12 percent

●Hematochezia (possibly representing necrotizing enterocolitis of the appendix) – 10 percent

●Irritability – 9 percent

The diagnosis of true appendicitis in a newborn may warrant evaluation for Hirschsprung disease [41]. More often, the findings of neonatal appendicitis are nonspecific and overlap with other more common neonatal surgical diseases, especially necrotizing enterocolitis. (See 'Neonatal appendicitis' below.)

Young children (<5 years) — Appendicitis is less prevalent in preschool children than children >5 years of age. Fever and diffuse abdominal tenderness with rebound or guarding are the predominant physical findings although irritability, grunting respirations, difficulty with or refusal to ambulate, and right hip complaints may also be present. Because they are more likely than older children to present with advanced appendicitis, rebound diffuse tenderness, and guarding are often present.

Typical findings on history are nonspecific such as fever, vomiting, and abdominal pain, all of which can also occur with other surgical diagnoses such as intussusception. Diarrhea is also relatively common making appendicitis difficult to differentiate from acute gastroenteritis, a much more common condition in these patients [29,30,32]. Children with appendicitis often have "diarrhea" that arises from the inflamed appendix or an associated abscess abutting the rectosigmoid colon that exerts pressure on the rectum and causes tenesmus with frequent, small volume, mucous stools that are nonodorous. By contrast, children with gastroenteritis and diarrhea usually have large volume, malodorous diarrhea. (See 'Differential diagnosis' below.)

Direct inflammation of the bladder by an inflamed appendix may also result in dysuria and frequency. Urinalysis may show leucocytes without the presence of bacteria or nitrates. (See 'Laboratory testing' below.)

Based upon observational studies, the relative frequency and variability of clinical findings in infants and children younger than five years is as follows [29,30,32]:

●Abdominal pain – 72 to 94 percent

●Fever – 62 to 90 percent

●Vomiting – 80 to 83 percent

●Anorexia – 42 to 74 percent

●Rebound tenderness – 81 percent

●Guarding – 62 to 72 percent

●Diffuse tenderness – 56 percent

●Localized tenderness – 38 percent

●Abdominal distension – 35 percent

●Diarrhea (frequent, low volume, with or without mucus) – 32 to 46 percent

School-age (5 to 12 years) — Appendicitis is more common in this age group than younger children, and although there are exceptions, they are more likely to the "classic" presentation described above. (See 'Common signs and symptoms' above.)

The relative frequency of these findings is illustrated in an observational study of 379 children 3 to 12 years (84 children under five years of age) [31]:

●Anorexia – 75 percent

●Vomiting – 66 percent

●Fever – 47 percent

●Diarrhea – 16 percent

●Nausea – 79 percent

●Maximum abdominal tenderness in the right lower quadrant – 82 percent

●Difficulty walking – 82 percent

●Pain with percussion, hopping, or coughing – 79 percent

Adolescent — The clinical features of appendicitis in this age group are similar to those in adults and often include the classic findings of fever, anorexia, periumbilical abdominal pain that migrates to the right lower quadrant, and vomiting. Involuntary guarding and rebound tenderness are present more often with perforation. The onset of pain typically occurs before vomiting and is a sensitive indicator of appendicitis. (See 'Clinical manifestations' above and "Acute appendicitis in adults: Clinical manifestations and differential diagnosis", section on 'Clinical manifestations'.)

Information regarding menstrual history and sexual activity can be helpful in distinguishing gynecologic disorders from appendicitis in perimenarchal females. Common conditions that may mimic appendicitis include (see 'Other nonsurgical diagnoses' below):

●Mittelschmerz (see "Evaluation of acute pelvic pain in female children and adolescents", section on 'Mittelschmerz')

●Ovarian cysts (see "Ovarian cysts in infants, children, and adolescents")

●Ovarian torsion (see "Ovarian and fallopian tube torsion")

●Ectopic pregnancy (see "Ectopic pregnancy: Clinical manifestations and diagnosis")

●Pelvic inflammatory disease (see "Pelvic inflammatory disease: Clinical manifestations and diagnosis")

Abdominal examination

Approach and analgesia — Despite its limitations, a careful abdominal examination is essential to the diagnosis of pediatric appendicitis. A reliable examination requires that the child be quiet and cooperative [3]. Similarly, the child can be initially examined in the position in which they are most comfortable, such as a caretaker's lap, prior to a standard evaluation.

In some patients, the degree of pain makes physical examination of the abdomen challenging. Patients with acute appendicitis often require analgesia to tolerate examination. Analgesia should be tailored to the degree of pain; some patients may require opioid therapy. It is not necessary to withhold opioid therapy out of concern that it may mask clinical signs and/or cloud the diagnosis. This approach is consistent with guidance from the American Academy of Pediatrics [42,43].

In the past, analgesia for patients with appendicitis was discouraged in the mistaken belief that pain control would mask symptoms and cause clinicians to miss definitive signs of disease. However, the available clinician trial data do not support this notion and suggest that diagnosis of appendicitis is not significantly impacted when opioid medications are given for pain control. In two trials involving nearly 200 children with suspected appendicitis who were randomly assigned to receive analgesia with intravenous morphine or placebo (saline), morphine administration did not delay surgical decision-making or increase the risk of perforation or missed appendicitis [44,45]. While children <5 years old were excluded from these trials, it is reasonable to extrapolate these findings to younger children.

In addition, multiple trials in adults with acute abdominal pain have demonstrated that analgesia does not negatively impact diagnostic accuracy. (See "Evaluation of the adult with nontraumatic abdominal or flank pain in the emergency department", section on 'Analgesia'.)

Physical findings — Local tenderness with some rigidity of the abdominal wall at or near McBurney's point (located approximately one-third of the distance along a line from the anterior superior iliac spine to the umbilicus) is the most reliable clinical sign of acute appendicitis. This finding may be less obvious when the appendix is in the retrocecal, retroileal, or pelvic position.

However, abdominal examination findings of appendicitis in children vary significantly by age and frequently fall outside of the classic disease presentation. (See 'Common signs and symptoms' above and 'Clinical features by age' above.)

The following features may also be noted on abdominal examination [3]:

●Children with appendicitis prefer to lie still, often with one or both hips flexed. They are generally comfortable as long as they are not disturbed.

●Peritoneal inflammation causes splinting, which reduces movement of the anterior abdominal wall during normal breathing.

●Generalized abdominal tenderness with some rigidity of the abdominal wall occurs in most patients with diffuse peritonitis due to acute appendicitis and perforation.

●Abdominal pain can also be elicited by asking the child to cough or to hop on one foot. Patients whose appendix is in the retrocecal, retroileal, or pelvic position may have less obvious discomfort with these maneuvers.

●Gentle percussion tenderness (tapping on the abdomen) over the right lower quadrant also suggests peritonitis. Although rebound tenderness is also a reliable sign of peritoneal irritation, many pediatric surgeons feel that testing for it is often unnecessary, since it is painful in children who have appendicitis and may be falsely positive in those who do not.

Other findings — The following findings are sometimes present in children with appendicitis but, with the exception of low-grade fever, are less helpful for establishing the diagnosis:

●Low grade fever (38 to 38.5°C [100.2 to 101°F]), or in neonates, temperature instability

●Limp or right hip pain

●Difficulty ambulating, especially among children with advanced appendicitis

●Lethargy or irritability (neonates and young infants)

●Right sided pelvic pain or mass on abdominal palpation or digital rectal examination

Based upon a systematic review of five articles, the sensitivity and specificity for diagnosing acute appendicitis using digital rectal examination are low in both adults and children (44 to 55 percent and 44 to 75 percent, respectively) [46]. Furthermore, in one observational study, the diagnostic accuracy for appendicitis in 33 children undergoing digital rectal examination was not different from 64 children in whom it was omitted (75 versus 90 percent, respectively) [47]. Thus, digital rectal examination is not necessary in most children with suspected appendicitis and typically does not need to be performed to make the diagnosis of appendicitis. In our experience, it may be helpful in equivocal cases when performed by an experienced examiner.

Laboratory testing — Laboratory tests combined with the history and physical examination can help raise or lower the clinical likelihood of appendicitis in children and guide the diagnostic approach. However, the clinician should not use laboratory tests in isolation to establish the diagnosis. Although limited in their ability to differentiate appendicitis from other causes of abdominal pain, we typically obtain the following studies:

●White blood cell count (WBC) and absolute neutrophil count (ANC) – Up to 96 percent of children with appendicitis have elevation of either the WBC or the ANC [23]. This finding, however, is nonspecific because many other diseases that mimic appendicitis (eg, streptococcal pharyngitis, pneumonia, pelvic inflammatory disease, or gastroenteritis) also cause leukocytosis and neutrophilia [3,48-50]. In a meta-analysis of 67 studies (nearly 35,000 children, over 13,300 with appendicitis), the pooled sensitivity for a WBC ≥10,000/mm³ was 85 percent (95% CI 80 to 89 percent) and for an ANC ≥7,500/mm³ was 90 percent (95% CI 85 to 94 percent) [51]. However, specificity was lower (58 percent for WBC and 63 percent for ANC).

Similarly, normal values for WBC or ANC in children undergoing evaluation for appendicitis have been used to predict a low risk of appendicitis as a component of validated clinical scoring systems [52-55]. (See 'Clinical scoring systems' below.)

●C-reactive protein (CRP) – Because CRP has not shown better sensitivity or specificity by itself compared with either WBC or ANC, it is not recommended by some experts [51,56,57]. However, when both WBC and CRP are obtained, sensitivity for appendicitis increases (97 percent [95% CI 93 to 99 percent] for either WBC ≥10,000/mm³ or CRP >10 mg/L) [51]. Also, when elevated, the height of the CRP provides predictive value for complicated appendicitis [58-61]. Thus, for children with suspected appendicitis, some experts obtain WBC, ANC, and CRP.

●Urinalysis – A urinalysis is usually performed in children with suspected appendicitis to identify alternative conditions such as a urinary tract infection (UTI) or nephrolithiasis. However, patients with appendicitis may have pyuria, although bacteria are not typically present in a clean-catch specimen [24]. Less commonly, hematuria may also occur due to appendiceal irritation of the ureter or bladder [62,63]. in patients with other features of alternative diagnoses such as UTI or kidney stones, these findings can significantly lower the likelihood of appendicitis. However, the clinician should not use the presence of pyuria or hematuria on urinalysis alone to dismiss the diagnosis of appendicitis.

●Urine pregnancy test (postmenarcheal females) – The clinician should also obtain a pregnancy test (urine beta-human chorionic gonadotropin) in postmenarcheal females to aid in the diagnosis of ectopic pregnancy and to guide imaging decisions in patients who have a moderate to high risk of appendicitis.

Procalcitonin (PCT) has low sensitivity and high specificity for appendicitis in children. For example, in a meta-analysis of six studies (860 children, 54 percent with appendicitis) PCT had a pooled sensitivity of 30 percent and pooled specificity of 83 percent for thresholds ranging from 0.1 to 0.5 ng/mL [51]. Because combinations of WBC, ANC, or CRP outperform PCT in children with appendicitis, PCT does not add sufficient additional diagnostic certainty to justify its inclusion as a routine test in children with suspected appendicitis.

EVALUATION AND DIAGNOSIS

Clinical suspicion — Acute appendicitis remains a clinical diagnosis and should be considered in all children with a history of abdominal pain and abdominal tenderness on physical examination. The diagnosis may be straightforward when the classic findings associated with appendicitis are present. However, the variations in presentation by age and sex can pose a significant challenge. Imaging, which is obtained in most patients, can help with the diagnosis of appendicitis, especially in patients who do not have the classic findings of appendicitis. It is also helpful in identifying abscess formation that may benefit from initial nonoperative care. (See 'Clinical manifestations' above and 'Clinical features by age' above.)

In some children with abdominal pain a clear alternative diagnosis is present (eg, streptococcal pharyngitis, pneumonia, pelvic inflammatory disease). These patients should receive specific treatment for the underlying condition rather than undergoing a diagnostic evaluation for appendicitis. (See 'Differential diagnosis' below.)

For patients without a clear etiology for their abdominal pain in whom appendicitis is suspected, we suggest a diagnostic approach guided by the clinical impression of risk (low, moderate, or high) derived from history, physical examination, and selected laboratory studies as follows (algorithm 1):

●Low risk – These patients have few signs or symptoms of appendicitis (eg, afebrile, no history of vomiting or anorexia, minimal diffuse abdominal tenderness with a soft abdomen on palpation, or no right lower quadrant tenderness). If obtained, white blood cell (WBC) count, absolute neutrophil count (ANC), and C-reactive protein (CRP) are typically normal.

Alternatively, patients can be determined to be low risk by a Pediatric Appendicitis Score (PAS) ≤2 (table 1) or according to the refined Low-Risk Appendicitis Rule (ANC <6750/mm³ AND either maximal abdominal tenderness not in the right lower quadrant or right lower quadrant tenderness but no abdominal pain with walking, jumping, or coughing) [52-55]. (See 'Clinical scoring systems' below.)

•Further evaluation – Children with a clear alternative diagnosis should undergo specific treatment for the identified condition; no further evaluation for appendicitis is indicated.

Patients without an obvious alternative diagnosis may still have appendicitis, especially if signs or symptoms are of a short duration (<24 hours). For example, up to 2 percent of patients categorized as low risk by the PAS and up to 7 percent of patients identified as low risk by the refined Low-Risk Appendicitis Rule ultimately have appendicitis [52-55]. However, the risk of appendicitis in these patients is low enough to make close follow-up the most appropriate approach.

Children without right lower quadrant pain or tenderness may be discharged home with clear instructions to the caregivers to return if pain increases or becomes localized to the right lower quadrant. The clinician should ensure that the caregivers are reliable and understand that a specific diagnosis for their child's abdominal pain has not been made and appendicitis is still possible.

Patients with right lower quadrant pain or tenderness should undergo assured reevaluation within 12 to 24 hours. Some clinicians may choose to admit children with right lower quadrant tenderness to the hospital for serial examination.

●Moderate risk – Children with a moderate risk for appendicitis have some signs or symptoms of appendicitis (eg, low-grade fever, vomiting or anorexia, right lower quadrant tenderness, or abdominal pain with walking, jumping, or coughing). The WBC, ANC, or CRP can be normal or elevated.

Alternatively, a PAS of 3 to 6 (table 1) suggests an intermediate risk of appendicitis that ranges from 8 to 48 percent. Patients who are not low risk by the refined Low-Risk Appendicitis Rule (ANC >6750/mm³ OR right lower quadrant tenderness with pain on walking, jumping, or coughing) have an estimated risk of appendicitis between 12 and approximately 50 percent. (See 'Clinical scoring systems' below.)

•Further evaluation – The best approach for these patients is not clear and depends upon local resources. Our approach is to obtain an ultrasound by a clinician with pediatric expertise; imaging results determine further care. (See "Acute appendicitis in children: Diagnostic imaging", section on 'Approach (moderate risk of appendicitis)'.)

If pediatric ultrasound imaging is not readily available, options include surgical consultation, diagnostic imaging (magnetic resonance imaging preferred), hospital admission with serial abdominal examinations by a surgeon with pediatric expertise, or a combination of these approaches.

●High risk – Children at high risk for appendicitis have classic findings of appendicitis, especially recent onset (one to two days) of abdominal pain that over time has migrated from the periumbilical region to the right lower quadrant followed by low-grade fever, vomiting, and anorexia and associated with right lower quadrant tenderness on physical examination. WBC, ANC, and/or CRP are typically elevated.

A PAS score ≥7 (table 1) indicates a high risk of appendicitis (50 to 60 percent). (See 'Clinical scoring systems' below.)

•Further evaluation – These children warrant prompt evaluation by a surgeon with pediatric expertise prior to urgent imaging to determine the need for appendectomy. If the patient requires transfer to a different hospital for pediatric surgical evaluation, then the clinician should defer diagnostic imaging (eg, ultrasound, computed tomography [CT], or magnetic resonance imaging [MRI]) if it will delay transfer or is likely not to be definitive. Otherwise, high rates of CT scan utilization may lead to significant unnecessary radiation exposure in children. For example, in a retrospective cohort of over 22,300 children who had appendectomies, presentation at a referral, nonchildren's hospital was the strongest predictor of CT use in children with appendicitis [64].

●Prior treatment with antibiotics – Prior treatment with antibiotics before surgical evaluation may modify the clinical findings or change decision making regarding surgical care in children with appendicitis as indicated by the following observational studies:

•In a retrospective study of 311 children treated for appendicitis, the 45 children who received antibiotics prior to evaluation had decreased tenderness on abdominal examination and had a higher degree of fever and elevated CRP prior to surgery than those not treated with antibiotics [65].

•In another study of 151 children, history of receiving antibiotics (50 patients) was strongly associated with a delay of 48 hours or longer in the diagnosis of appendicitis (OR 5.8, 95% CI 2.3-15.5) despite comparable physical findings suggestive of appendicitis (eg, right lower quadrant tenderness or peritoneal findings) in children who did or did not receive antibiotics.

Thus, prior treatment with antibiotics tends to lower the confidence regarding the clinical examination and diagnosis of appendicitis by the surgeon and may cause a delay in definitive diagnosis. Diagnostic imaging is usually warranted to supplement other clinical findings in these patients.

Clinical scoring systems — Several clinical scoring systems have been devised for the diagnosis of appendicitis [3]. Among these, the PAS (table 1), the refined Low-Risk Appendicitis Score, the Alvarado (or MANTRELS) score, and the Pediatric Appendicitis Risk Calculator (pARC) have been prospectively studied in children [3,66-70]. The utility of these scores lies in their ability to categorize patients into groups that are at low, moderate, and high risk of appendicitis.

Evidence is lacking to evaluate the ability of these scoring systems to improve diagnostic outcomes (ie, reduction in perforation and/or negative appendectomy rate) when compared with assessment by experienced clinicians. Because they have limited ability to identify patients who warrant appendectomy, clinicians should use clinical scoring systems as screening tools to guide surgical consultation and/or diagnostic imaging rather than diagnostic tools.

Interobserver reliability of historical and physical examination findings commonly used in these scores shows significant variation. As an example, in a prospective multicenter study of 811 children (age 3 to 18 years) with possible appendicitis who underwent independent evaluations by clinicians with variable experience and training, agreement beyond chance for items commonly used in clinical scores was high only for the history of emesis and was moderate for the following clinical features [71]:

●Anorexia

●Duration of pain

●Presence of right lower quadrant pain

●Migration of pain to the right lower quadrant

●Maximal tenderness in the right lower quadrant

●Abdominal pain with walking, jumping, or coughing

These findings may, in part, explain why diagnostic accuracy for clinical scoring systems can be inconsistent.

Limited evidence is available to determine which score is best. In one systematic review of 11 prospective studies that evaluated the use of the PAS in 2170 children and the Alvarado score in 1589 children, the Alvarado score appeared to be better than the PAS for identifying children at low risk for appendicitis [72]. However, the analysis showed marked heterogeneity among the reviewed studies including significant variation in the percent of patients with appendicitis (15 to 71 percent) [73].

Pediatric appendicitis score — The PAS is a tool that utilizes history, physical examination, and laboratory results to categorize the risk of appendicitis in children with abdominal pain on a 10-point scale (table 1) [52,66]. An algorithm that incorporates the PAS for clinical decision-making in children with suspected appendicitis is provided (algorithm 1).

Management according to the PAS is suggested by several studies [52-54,72,74,75] (see 'Clinical suspicion' above):

●A PAS ≤3 suggests a low risk for appendicitis. Children with a PAS score in this range may be discharged home as long as their caretakers understand that persistent pain or additional symptoms warrant repeat evaluation.

●A PAS ≥7 or 8 indicates a high risk for appendicitis. Children with a PAS score in this range warrant surgical consultation or urgent imaging depending upon local guidelines. It is unclear if the PAS alone can be used to determine the need for appendectomy, because the number of patients with high scores who do not have appendicitis varies widely. This variation may be due, in part, to differences in inclusion and exclusion criteria in the studies discussed above.

●A PAS of 3 to 6 or 7 is indeterminate for appendicitis. Our approach is to obtain an ultrasound by a clinician with pediatric expertise; imaging results, taken with physical findings and laboratory data will then determine further care. (See "Acute appendicitis in children: Diagnostic imaging", section on 'Approach (moderate risk of appendicitis)'.)

If timely access to ultrasound by a provider with pediatric expertise is not available, options include surgical consultation, diagnostic imaging (magnetic resonance imaging preferred), serial abdominal examinations while being observed in the hospital, or a combination of these approaches depending upon local resources.

In several prospective observational studies, the mean PAS was significantly higher in children with appendicitis than in children without appendicitis (7 to 7.5 versus 2 to 5, respectively) [52-54,74]. The frequency of appendicitis in these studies varies by PAS as follows:

●PAS ≤2 to 3 – 0 to 2 percent

●PAS 3 to 6 – 8 to 48 percent

●PAS ≥7 – 78 to 96 percent

In one prospective observational study of 101 children with abdominal pain, a PAS of ≤3 excluded the diagnosis of appendicitis with a sensitivity of 100 percent (95% CI 98 to 100 percent) and a negative predictive value of 100 percent (95% CI 96 to 100 percent, prevalence of appendicitis: 28 percent) [74]. A PAS ≥8 had relatively high specificity (93 percent) but low sensitivity (57 percent). By contrast, a systematic review of six prospective studies with a total of 2170 patients found that a cutoff of <4 for low risk of disease was not sufficiently accurate for excluding appendicitis although the analysis showed significant heterogeneity among the pooled studies and, for most studies, a relatively high prevalence of appendicitis [72]. This review also found that a PAS ≥8 was not accurate enough to diagnose appendicitis.

Clinical pathways that utilize the PAS have the potential to achieve acceptable diagnostic accuracy and low utilization of CT [76,77]. As an example, in a prospective observational study of 196 children with abdominal pain who were evaluated using a clinical pathway based upon the PAS to determine discharge (PAS ≤3), emergency ultrasonography (PAS 4 to 7), or surgery consult (PAS 8 to 10) in a children's hospital emergency department, the sensitivity and specificity of the pathway for appendicitis was 92 and 95 percent, respectively [76]. Perforated appendicitis occurred in 15 percent of patients and the negative appendectomy rate among the 68 children undergoing operation was 4.4 percent. CT of the abdomen was performed in 7 percent of patients. No child with a PAS ≤3 had appendicitis.

Refined Low-Risk Appendicitis Score — The Refined Low-Risk Appendicitis Score consists of the following low-risk items [55]:

●Absence of maximal tenderness in the right lower quadrant OR right lower quadrant tenderness without pain on walking, jumping, or coughing

●ANC less than 6750/mm³

In a prospective cohort of 2625 children evaluated at multiple centers, these criteria had a sensitivity of 98 percent, specificity of 24 percent, and negative predictive value of 95 percent in identifying children without appendicitis [55].

Alvarado score — The Alvarado score (also called the MANTRELS score) is a 10-point score derived from eight components:

●Migratory right iliac fossa pain (1 point)

●Anorexia (1 point)

●Nausea/vomiting (1 point)

●Tenderness in the right iliac fossa (2 points)

●Rebound tenderness in the right iliac fossa (1 point)

●Elevated temperature >37.5°C (1 point)

●Leukocytosis (2 points)

●Shift of the WBC count (1 point)

The Alvarado score does not have adequate accuracy for the diagnosis of appendicitis in children. In a systematic review of the diagnostic accuracy of the Alvarado score, which included 1075 children, a score of ≥5 for admission and ≥7 for surgery had pooled sensitivities of 99 percent and 76 percent among pediatric patients, respectively [78]. However, the Alvarado score had a significant tendency to exaggerate the probability of appendicitis in intermediate (score 5 or 6) and high (score 7 to 10) risk children. Furthermore, analysis suggested that the diagnostic accuracy of the score was inconsistent in children. In a separate systematic review of six prospective studies (1589 patients), no Alvarado score had an acceptable performance for ruling in appendicitis [72]. For example, using a score of ≥9 for the performance of surgery in children with a 40 percent pretest probability of appendicitis would have resulted in a 19 percent frequency of negative appendectomy [73]. On the other hand, this review also found that an Alvarado score <5 in children with a pretest probability for appendicitis up to 40 percent reduced the likelihood of appendicitis to <3 percent and which for some clinicians would permit the safe discharge of such patients to home observation. However, this risk of appendicitis is still greater than what is found for a Pediatric Appendicitis Score of 2 to 3. (See 'Pediatric appendicitis score' above.)

The use of the Alvarado score for the diagnosis and management of appendicitis in adults is discussed separately. (See "Acute appendicitis in adults: Diagnostic evaluation", section on 'Clinical scoring systems'.)

Pediatric appendicitis risk calculator (pARC) — The pARC has been derived and validated using prospectively collected clinical findings from almost 4000 children evaluated for abdominal pain at a single children’s hospital emergency department during three different time periods [70]. Using a risk score based upon patient age, sex, duration of pain, migration of pain to the right lower quadrant, maximal tenderness in the right lower quadrant, abdominal guarding, and ANC, the pARC predicted the risk for appendicitis with high discrimination (AUC 0.85) and outperformed the PAS in a validation cohort of almost 1500 children. During validation in over 2000 children with abdominal pain evaluated in 11 community emergency departments, the pARC score had higher discrimination for appendicitis than the PAS (AUC 0.89 versus 0.80, respectively) [79]. The negative appendectomy rate was 6.5 percent, and the perforation rate was 16 percent in this cohort.

Use of the pARC requires sophisticated calculations that must be programmed and integrated into an electronic health record, which may be a barrier to implementation in some settings. Furthermore, it is not clear that the pARC score reduces resource utilization (eg, imaging or surgical consultation) or improves clinical outcomes. For example, in a multicenter trial of almost 6,000 children (age 5 to 20 years) that compared sites that used the pARC score integrated into their electronic health record with sites assigned to usual care, diagnostic imaging, appendicitis with perforation, negative appendectomies, and cases of missed appendicitis were similar between the study groups [80].

Imaging — For children who do not have a typical presentation for appendicitis or in whom appendicitis cannot be excluded clinically, imaging can be helpful to establish or exclude the diagnosis. Ultrasonography and CT, separately or in combination, are the modalities used most frequently; although evidence suggests that MRI instead of CT can provide similar diagnostic accuracy in a timely manner without radiation exposure. (See "Acute appendicitis in children: Diagnostic imaging", section on 'Approach (moderate risk of appendicitis)'.)

We suggest the following approach to the use of imaging studies for children with suspected appendicitis (see 'Clinical suspicion' above and "Acute appendicitis in children: Diagnostic imaging", section on 'Who to image'):

●Children with a typical clinical presentation for acute appendicitis are likely to have appendicitis. For these patients at high risk for appendicitis, we suggest clinicians consult a surgeon with pediatric experience prior to obtaining urgent imaging studies.

●Children who have a low risk for appendicitis based upon the clinical examination and, when indicated, laboratory studies may be managed without imaging at the initial evaluation. These patients warrant clear instructions regarding signs of appendicitis that should prompt reevaluation, or if right lower quadrant pain or tenderness is present, assured reevaluation within 12 to 24 hours.

●Children with atypical or equivocal clinical findings of appendicitis suggesting a moderate likelihood for appendicitis warrant diagnostic imaging. Ultrasound is the preferred initial study, especially in adolescent females. Results of the ultrasound guide further care including surgical consultation.

●Adolescent females warrant a pelvic ultrasound with Doppler to evaluate for ovarian pathology and ectopic pregnancy.

Clinical scoring systems may be useful in establishing the level of risk in children with appendicitis. (See 'Clinical scoring systems' above.)

Neonatal appendicitis — Appendicitis in neonates is rare [25,81]. The low frequency of appendicitis in these patients is attributed to anatomic differences in the appendix (more funnel-shaped than tubular), soft diet, infrequent diarrheal illnesses, and recumbent positioning [81,82]. Neonatal appendicitis has been associated with preterm birth (gestational age <37 weeks) [26]. Differentiation from necrotizing enterocolitis is challenging. Furthermore, necrotizing enterocolitis may coexist with neonatal appendicitis [40]. In some neonates, atypical features such as localization of imaging findings to the cecum on plain radiographs and signs of perforation may point to the diagnosis of appendicitis [83,84]. Abdominal ultrasound can help confirm diagnosis in some, but not all cases [40,81]. In addition, up to one-third of neonates with appendicitis may present with the appendix contained in an inguinal hernia (Amyand hernia) and giving the appearance of an incarcerated inguinal hernia [27].

Total colonic and long-segment Hirschsprung disease may present in the neonatal period with perforation of the appendix and is reported in up to 5 percent of patients with neonatal appendicitis [40,81,85]. Diagnostic evaluation for Hirschsprung disease is indicated in patients with suggestive clinical findings (eg, history of delayed passage of meconium or explosive expulsion of gas and liquid stool after digital rectal examination [squirt sign or blast sign]). (See "Congenital aganglionic megacolon (Hirschsprung disease)", section on 'Evaluation'.)

Mortality from neonatal appendicitis occurs in approximately 25 percent of patients with abdominal appendicitis and reflects the difficulty in establishing the diagnosis prior to appendiceal perforation, peritonitis, and sepsis [81,86]. By contrast, neonates with inguinoscrotal appendicitis present as an incarcerated inguinal hernia that requires emergency surgery, thus mortality is rare for these patients.

Chronic or recurrent appendicitis — Chronic appendicitis refers to the pathologic finding of chronic inflammation or fibrosis of the appendix found in a subset of patients undergoing appendectomy. Chronic appendicitis is a rare finding in children. These patients are clinically characterized by prolonged (>7 days) right lower quadrant pain that may be intermittent and a normal WBC count. Most patients have resolution of pain with appendectomy. Crohn disease is a consideration in patients who have persistent pain after surgery.

Recurrent appendicitis can occur but is also rare in children; such cases may be caused by a retained foreign body (eg, fecalith) in the lumen of the appendix. Stump appendicitis is a form of recurrent appendicitis that is related to incomplete appendectomy that leaves an excessively long stump after open or laparoscopic surgery. (See "Acute appendicitis in children: Management", section on 'Late'.)

CLASSIFICATION — 

Classically, there are four stages of appendicitis [3,4]:

●Acute – Appendiceal lumen obstruction causes colic followed by reflex vomiting and referred periumbilical pain.

●Suppurative – Excess appendiceal mucosa secretion in response to obstruction leads to dilation of the appendix. As dilation increases, it produces bacterial overgrowth, venous congestion, bacterial invasion of the wall, and transmural inflammation. These changes cause pain localized to the appendix, most commonly found in the right lower quadrant.

The bacteria present include the usual fecal flora consisting of aerobic and anaerobic Gram negative rods. The most common include Escherichia coli, Peptostreptococcus species, Bacteroides fragilis, and Pseudomonas species [87].

●Gangrenous – Increased appendiceal lumen pressure results in compromised arterial flow and ischemia of the appendix. Initially, this results in microperforation with bacterial contamination outside of the appendix.

●Perforated – As ischemia progresses, frank perforation occurs marked by:

•Visible hole in the appendix at operation

•Abscess

•Extraluminal fecalith

•Diffuse fibrinopurulent exudate extending outside the right lower quadrant and pelvis

•Generalized peritonitis if the infection is not contained by bowel loops and omentum

Perforation occurs rarely in the first 12 hours of symptoms but is more likely as time passes, becoming common after 72 hours.

More recently, experts typically describe appendicitis as (see "Acute appendicitis in children: Management", section on 'Terminology'):

●Early or uncomplicated, which includes acute and suppurative appendicitis

●Advanced or complicated, which includes transmural bacterial contamination of the peritoneal cavity in gangrenous or perforation appendicitis

Classification of the type of appendicitis (uncomplicated versus complicated) is not always possible prior to appendectomy.

DIFFERENTIAL DIAGNOSIS — 

Appendicitis often presents with characteristic clinical features that make the evaluation and diagnosis straightforward. However, many diseases can mimic acute appendicitis in children and adolescents (table 2). (See "Causes of acute abdominal pain in children and adolescents".)

Emergency surgical diagnoses — Although conditions other than appendicitis may also require operative management, the urgency and surgical approach may vary depending upon the diagnosis.

●Bowel obstruction – Bowel obstruction must always be considered in the child who has had abdominal surgery and presents with vomiting and abdominal pain. Vomiting may be bilious. In addition, plain films of the abdomen often show distended loops of bowel with air-fluid levels or pneumoperitoneum. However, appendicitis is the most common cause of bowel obstruction in children who have not had previous abdominal surgery.

●Intestinal malrotation – Although most children with malrotation present in infancy with abdominal distension and bilious vomiting, a small percentage are diagnosed outside of infancy with abdominal pain and a variety of nonspecific clinical findings. Patients with volvulus often have pain out of proportion to physical examination findings. In patients with signs of obstruction, plain abdominal radiographs should be performed to exclude signs of perforation. The diagnosis of malrotation is confirmed by a limited upper gastrointestinal series, abdominal ultrasound, or CT of the abdomen with intravenous contrast. Prompt surgical intervention is required in patients with volvulus. (See "Intestinal malrotation in children", section on 'Diagnosis'.)

●Intussusception – Intussusception describes invagination of a part of the intestine into itself. Patients typically have an abrupt onset of intermittent episodic abdominal pain with vomiting, blood in the stool, and less commonly, lethargy or a palpable sausage-shaped abdominal mass in the right upper quadrant. In the hands of an experienced ultrasonographer, the sensitivity and specificity of ultrasound for establishing the diagnosis of intussusception approach 100 percent. The diagnosis can also be made with a contrast enema (air or barium), which may reduce the intussusceptum, thereby avoiding an operation. (See "Intussusception in children", section on 'Evaluation'.)

●Ovarian torsion – Although ovarian torsion does not occur commonly in children, the presentation is nonspecific and easily confused with appendicitis. Features include an acute onset of moderate to severe abdominal pain, vomiting, and an adnexal mass. The character of the pain may be sharp, stabbing, colicky, or crampy, and may radiate to the flank, back, or groin. Infants with ovarian torsion present with feeding intolerance, vomiting, abdominal distension, and fussiness or irritability. Most infants have previously diagnosed ovarian cysts on prenatal ultrasounds. Salvage of the ovary is often not possible but is maximized by expeditious surgery. Ovarian torsion is typically diagnosed with Doppler flow ultrasound of the ovaries. Imaging for ovarian torsion is discussed in detail separately. (See "Ovarian and fallopian tube torsion", section on 'Clinical presentation' and "Ovarian and fallopian tube torsion", section on 'Imaging studies'.)

●Ectopic pregnancy – Ectopic pregnancy can be a life-threatening emergency typically occurring six to eight weeks after the last normal menstrual period. Classic symptoms include abdominal pain, vaginal bleeding, and amenorrhea. Normal signs of pregnancy such as breast tenderness, frequent urination, and nausea may also be present. Clinical findings, a positive urine pregnancy test, and visualization of a pregnancy outside of the uterus are the key diagnostic findings. (See "Ectopic pregnancy: Clinical manifestations and diagnosis", section on 'Clinical presentation' and "Ectopic pregnancy: Clinical manifestations and diagnosis", section on 'Diagnosis'.)

●Testicular torsion – Although testicular torsion can cause abdominal pain, symptoms and physical findings in the scrotum will also be present. (See "Causes of scrotal pain in children and adolescents", section on 'Testicular torsion'.)

●Torsion of the omentum – Omental torsion may cause localized right-sided abdominal pain and tenderness [88,89]. Fever and vomiting are less prominent than in acute appendicitis. Obesity appears to be a risk factor. Ultrasound or CT can aid in diagnosis by identifying an ovoid mass with adherence to the anterior abdominal wall [89]. The signs and symptoms will often resolve with intravenous fluids and analgesia. If this diagnosis is recognized by ultrasound or CT before surgery, operation is not necessary. When diagnosed intraoperatively, treatment consists of partial omentectomy. Omental torsion coexisting with appendicitis has been described [88,90].

Emergency nonsurgical diagnoses — Most nonsurgical diagnoses that may be confused with appendicitis can usually be detected early in the evaluation of children with acute abdominal pain. Failure to do so, however, could delay emergency disease-specific treatment.

●Hemolytic uremic syndrome – Children with hemolytic uremic syndrome often have vomiting and abdominal pain with a prodrome of diarrhea. The characteristic triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure is also typically present, leading to a prompt diagnosis. (See "Clinical manifestations and diagnosis of Shiga toxin-producing Escherichia coli (STEC) hemolytic uremic syndrome in children".)

●Diabetic ketoacidosis – Children with diabetic ketoacidosis usually have classic symptoms such as polyphagia, polydipsia, and polyuria. Once insulin deficiency and ketoacidosis become significant, anorexia, vomiting, and abdominal pain develop in association with hyperglycemia, metabolic acidosis, glycosuria, and ketonuria. (See "Diabetic ketoacidosis in children: Clinical features and diagnosis".)

●Primary peritonitis – Primary peritonitis usually occurs in children with ascites and chronic conditions such as nephrotic syndrome, systemic lupus erythematosus, or liver disease although cases caused by Streptococcus pyogenes have been described in healthy children [91]. In patients with ascites, the diagnosis is made by paracentesis with isolation of a single organism by culture in association with an ascitic fluid neutrophil count ≥250 cells/mm³. Differentiation of primary peritonitis from secondary peritonitis caused by a surgical condition is a critical aspect of care and is discussed in greater detail separately. (See "Spontaneous bacterial peritonitis in adults: Diagnosis", section on 'Distinguishing spontaneous from secondary bacterial peritonitis'.)

Other nonsurgical diagnoses — Nonsurgical diagnoses that present in a similar manner to appendicitis often have some distinguishing features. Others, such as pneumonia, streptococcal pharyngitis, and urinary tract infections (UTIs) may not be recognized unless specific ancillary studies are performed.

●Gastroenteritis – Gastroenteritis occurs commonly in children younger than two years. In resource-rich countries, a viral etiology is most common, and the presence and quantity of diarrhea can be variable. Diarrhea may also occur in children with appendicitis, especially patients younger than five years of age. In most instances, children with gastroenteritis have diffuse abdominal tenderness without guarding or rebound tenderness. The diagnosis of gastroenteritis should be made cautiously in children with abdominal pain and vomiting who do not have diarrhea. In one retrospective review of cases of missed appendicitis, 42 percent of children were initially diagnosed with gastroenteritis [24]. (See "Acute viral gastroenteritis in children in resource-abundant countries: Clinical features and diagnosis", section on 'Clinical presentation'.)

Yersinia enterocolitica gastroenteritis can cause focal abdominal pain that is clinically indistinguishable from appendicitis. (See "Yersiniosis: Infection due to Yersinia enterocolitica and Yersinia pseudotuberculosis", section on 'Pseudoappendicitis'.)

●Pneumonia – An infiltrate in the lower lobes of the lungs may irritate the diaphragm and cause abdominal pain that can mimic findings of appendicitis in children. Cough, fever, tachypnea, rales on auscultation, and/or decreased oxygen saturation help to distinguish pneumonia from appendicitis. In many children, pneumonia can be diagnosed based upon clinical findings alone. The presence of infiltrates on chest radiograph, which may be subtle on presentation, confirms the diagnosis of pneumonia in children with compatible clinical findings. However, pneumonia can be difficult to identify when respiratory signs and symptoms are subtle [92]. Because of the overlap in clinical presentation, some children with suspected appendicitis may warrant chest radiographs and abdominal imaging. (See "Community-acquired pneumonia in children: Clinical features and diagnosis", section on 'Clinical presentation' and "Fever without a source in children 3 to 36 months of age: Evaluation and management", section on 'Pneumonia' and "Community-acquired pneumonia in children: Clinical features and diagnosis", section on 'Diagnosis'.)

●Urinary tract infection – UTIs may cause abdominal pain and vomiting, particularly in young children. Although white blood cells (WBCs) may also be seen on urinalysis in patients with appendicitis, children with UTIs will generally have bacteria on microscopic examination and a dipstick positive for leukocyte esterase and/or nitrites. (See "Urinary tract infections in infants older than one month and children younger than two years: Clinical features and diagnosis", section on 'Rapidly available tests'.)

●Streptococcal pharyngitis – Young children with streptococcal pharyngitis may have vomiting and abdominal pain in addition to a sore throat. Suggestive clinical findings include sore throat, tender anterior cervical nodes, and exudative pharyngitis. Rapid antigen detection can quickly diagnose group A streptococcal disease in most cases. (See "Group A streptococcal tonsillopharyngitis in children and adolescents: Clinical features and diagnosis", section on 'Diagnosis'.)

●Mesenteric lymphadenitis – Children with abdominal pain who undergo ultrasound demonstrate mesenteric lymphadenitis in 9 to 32 percent of cases [93,94]. This radiologic finding is a nonspecific indicator of infection, inflammation, and rarely, malignancy. Etiologies of mesenteric lymphadenitis include viral and bacterial gastroenteritis, inflammatory bowel disease, and lymphoma. (See "Causes of acute abdominal pain in children and adolescents", section on 'Gastrointestinal'.)

Compared with patients with acute appendicitis, children with mesenteric adenitis tend to have longer duration of symptoms prior to presentation, fewer findings of appendicitis (ie, vomiting, migration of pain, percussion tenderness, rebound tenderness, or Rovsing sign), higher fever (when present), and normal WBC counts and C-reactive protein (CRP) levels [95]. However, patients with mesenteric adenitis can have clinical findings that are difficult to distinguish from acute appendicitis [96]. Ultrasound is typically warranted to make the diagnosis and to exclude appendicitis.

●Pelvic inflammatory disease (PID) – Although PID usually causes diffuse lower abdominal pain, focal right lower quadrant abdominal pain does occur. Patients may often be febrile. Findings on pelvic bimanual examination of a purulent endocervical discharge and/or acute cervical motion and adnexal tenderness distinguish PID from appendicitis. (See "Pelvic inflammatory disease: Clinical manifestations and diagnosis".)

●Ovarian cyst – Ovarian cysts commonly occur in postmenarcheal adolescent females and may cause right lower quadrant pain, which can be severe if the cyst has ruptured. Findings of anorexia and vomiting are less common unless ovarian torsion has occurred. Plain and Doppler ultrasounds of the pelvis and abdomen that demonstrate an ovarian cyst and a normal appendix are diagnostic. (See "Ovarian cysts in infants, children, and adolescents", section on 'Epidemiology and pathogenesis'.)

●Mittelschmerz – This ovulatory event causes recurrent midcycle pain in females with regular ovulatory cycles. This pain is caused by normal follicular enlargement just prior to ovulation or to normal follicular bleeding at ovulation. The pain is typically mild and unilateral; it occurs midway between menstrual periods and lasts for a few hours to a couple of days. The onset of pain midcycle and a history of recurrence help to differentiate mittelschmerz from appendicitis. (See "Evaluation of acute pelvic pain in female children and adolescents", section on 'Mittelschmerz'.)

●Nephrolithiasis – Kidney stones are less common than appendicitis in children. In children, intermittent colicky flank pain with radiation to the abdomen and groin is a common manifestation, which may be accompanied by gross or microscopic hematuria. Diagnosis can be confirmed by ultrasound or by helical CT of the abdomen and pelvis. (See "Nephrolithiasis (kidney stones) in children: Clinical features and diagnosis", section on 'Clinical presentation' and "Nephrolithiasis (kidney stones) in children: Clinical features and diagnosis".)

●Sickle cell disease – Abdominal pain as a result of infarction of abdominal and retroperitoneal organs can occur in children with sickle cell disease. Although vaso-occlusive crises occur more commonly than appendicitis, the symptoms may be indistinguishable [97,98]. A surgical diagnosis should be considered in patients with an unusual pattern of pain or who do not respond promptly to hydration and analgesia. (See "Overview of the clinical manifestations of sickle cell disease".)

●Immunoglobulin A vasculitis (IgAV; Henoch-Schönlein purpura [HSP]) – IgAV (HSP) is a systemic vasculitis that includes a characteristic purpuric rash, typically distributed symmetrically over the upper legs and buttocks (picture 1). Abdominal pain is usually colicky and may be associated with vomiting. Intussusception is a rare surgical complication. (See 'Emergency surgical diagnoses' above and "IgA vasculitis (Henoch-Schönlein purpura): Clinical manifestations and diagnosis".)

SOCIETY GUIDELINE LINKS — 

Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Appendicitis in children".)

INFORMATION FOR PATIENTS — 

UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Appendicitis in adults (The Basics)" and "Patient education: Appendicitis in children (The Basics)")

SUMMARY AND RECOMMENDATIONS

●Clinical manifestations – The classic presentation of appendicitis includes the following historical and physical examination findings (see 'Clinical manifestations' above):

•Anorexia

•Periumbilical pain (early)

•Migration of pain to the right lower quadrant (often within 24 hours of onset of symptoms)

•Pain with movement – walking or shifting position in bed or on the stretcher

•Vomiting (typically occurring after the onset of pain)

•Fever (commonly occurring 24 to 48 hours after onset of symptoms)

•Right lower quadrant tenderness

•Signs of localized or generalized peritoneal irritation (eg, rebound, guarding, tenderness with coughing or hopping)

Although this classic pattern of clinical findings does occur in school-age children and adolescents, it is less common overall in pediatric patients with appendicitis than in adults and may not occur at all in children younger than five years of age. (See 'Clinical features by age' above.)

●Abdominal examination – A reliable abdominal examination is key to demonstrating the physical findings of appendicitis and requires a quiet and cooperative patient. Children with acute appendicitis often require analgesia to tolerate examination. Analgesia should be tailored to the degree of pain; some patients may require opioid therapy. It is not necessary to withhold opioid therapy out of concern that it may mask clinical signs and cloud the diagnosis. (See 'Approach and analgesia' above.)

Local tenderness with some rigidity of the abdominal wall is the most reliable clinical sign of acute appendicitis. This finding may be less obvious when the appendix is in the retrocecal, retroileal, or pelvic position. However, examination findings of appendicitis in children vary significantly by age and frequently fall outside of the classic disease presentation. (See 'Physical findings' above and 'Clinical features by age' above.)

●Laboratory testing – Although limited in their ability to differentiate appendicitis from other causes of abdominal pain, results of the following laboratory tests can raise or lower the likelihood of appendicitis in children and aid in the diagnostic process (see 'Laboratory testing' above):

•White blood cell (WBC) count

•Differential with calculation of the absolute neutrophil count (ANC)

•C-reactive protein (CRP)

•Urinalysis

•Urine pregnancy test in postmenarcheal females

●Diagnosis – The diagnosis of appendicitis in children relies on an evaluation that provides an estimated risk for appendicitis (low, moderate, or high) derived from clinical findings. Several validated clinical scoring systems have been developed to assist in this process.

An algorithm that incorporates the Pediatric Appendicitis Score (PAS) to guide the use of imaging and identify children with suspected appendicitis who need surgical consultation is provided (algorithm 1). (See 'Clinical suspicion' above and "Acute appendicitis in children: Diagnostic imaging", section on 'Who to image'.)

●Differential diagnosis – Children whose evaluation indicates a clear alternative diagnosis should undergo specific treatment for the identified condition and no further evaluation for appendicitis is necessary. (See 'Differential diagnosis' above.)

ACKNOWLEDGMENT — 

The UpToDate editorial staff acknowledges David E Wesson, MD, who contributed to earlier versions of this topic review.