Chapter X.3. Appendicitis
Ian K.H. Chun
October 2022

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The editors and current author would like to thank and acknowledge the significant contribution of the previous author of this chapter from the 2002 first edition Dr. Walton Shim. This current third edition chapter is a revision and update of the original author’s work.

A 7-year-old girl presents to the emergency department (ED) with a chief complaint of abdominal pain for one day. Mid-abdominal pain started after lunch yesterday. This was followed by non-bilious vomiting and an episode of loose stools without blood, which did not relieve the pain. The patient did not feel like eating dinner and went to bed but had a restless night due to abdominal pain. By morning the pain had worsened, and she vomited again. The pain migrated towards the right lower quadrant (RLQ) and is worse with movement. There is no history of fever, coughing, chest pain, dysuria, urinary frequency, sore throat, rash.

Exam: VS T 37.1, R 20, HR 140, BP 130/80. As the patient enters the exam room, she walks slowly and slightly hunched over. She is alert but subdued. HEENT Negative. Neck is supple. Chest is clear. Heart regular without murmur. Abdomen: bowel sounds hypoactive with focal right lower quadrant tenderness and guarding. No organs or masses are felt. Right lower quadrant rebound tenderness is present. No inguinal hernias.

Acute appendicitis is highly suspected on clinical grounds. Labs are drawn and an IV fluid infusion is initiated. A surgeon is called and he requests lab studies and an ultrasound.

CBC WBC 14.0, 60% Segs, 15% Bands. UA 10-15 WBC, 15-20 RBC, no bacteria. The ultrasound shows an enlarged appendix measuring 7 mm in diameter. No fecalith is seen. There is a small amount of pelvic fluid.

The surgeon evaluates the patient in the ED. IV piperacillin-tazobactam is ordered and the patient is scheduled for laparoscopic appendectomy. An inflamed non-perforated appendix is identified and an appendectomy is performed. The patient does well postoperatively.

The recorded history of appendicitis begins in 1886 when the pathologist Reginald Fitz of Boston first described the condition of "appendicitis", and in 1887, the Philadelphia surgeon T.G. Morton performed the first successful removal of a perforated appendix (1). Charles McBurney immortalized "McBurney's point" when he described it in 1889 as the point of greatest tenderness located 1.5 to 2 inches (4 to 5 cm) from the anterior spine of the ileum on a line drawn between that point and the umbilicus.

It is estimated that approximately 70,000 children are diagnosed with appendicitis annually in the United States, making it the most frequently performed emergency medical procedure in childhood (2). About one third of all patients with acute appendicitis are under the age of 18 with a peak incidence between 11 and 12 years old. Overall mortality rates of appendicitis range between 0.2% to 0.8% in adults and 0.1% to 1% in children.

Obstruction of the lumen by impacted fecal material is a common cause of appendicitis accounting for 30% of pediatric appendicitis cases while only representing about 14% of adult appendicitis (3). Lymphoid hyperplasia or mucosal inflammation from bacterial infections such as Yersinia, Shigella, Salmonella, or from viral or parasitic infection can also cause appendiceal obstruction. Regardless of etiology, the obstruction creates an increase in intraluminal pressure and edema which leads to venous outflow obstruction. As a consequence of this outflow obstruction, the appendix can become ischemic with the development of mucosal ulceration leading to infection and perforation which can then lead to generalized peritonitis or an appendiceal abscess (2).

The diagnosis of acute appendicitis is a good example of critical thinking in medicine. It involves both inductive and deductive reasoning. It starts with a chief complaint, or the reason the patient comes to see the physician, followed by a probing evaluation and expansion of the chief complaint into what amounts to a history of symptoms surrounding the chief complaint or the present illness.

The most common presenting symptom of acute appendicitis is mid-abdominal or epigastric abdominal pain associated with anorexia and vomiting. This is because early obstruction and edema of the appendiceal lumen as well as colicky pain of the entire intestinal tract is most often appreciated in the mid-abdomen or epigastrium. As the process of obstruction proceeds to edema and inflammation of the appendiceal wall and serosa, pain starts to localize in the dermatome overlying the infected appendix in the right lower quadrant (4). Anorexia, vomiting, and/or pain with walking can occur. There can be sudden pain relief with appendiceal rupture only to have more intense symptoms recur as peritonitis becomes established. There is great variability in the history and it is often difficult to obtain a reliable history in young children.

Although abdominal pain is the most common presenting symptom, respiratory, genitourinary, gynecological, lymphatic, neurologic, and other non-surgical etiologies can cause abdominal pain. Therefore, the diagnostician must ask whether the child has a respiratory infection with cough, sore throat or chest pain; whether or not there is radiation around the right flank or dysuria and groin pain indicating a urological cause; or in a girl, whether or not the pain radiates to the anterior right thigh indicating pain of ovarian origin. In post menarchal females, low abdominal pain occurring in mid-cycle may be caused by a ruptured ovarian follicle which is called mittelschmerz (literally, middle pain). Infected lesions of the right lower extremity may cause acute femoral and/or iliac lymphadenitis and tenderness. Neurological causes such as nerve root pain should also be considered. With the elimination of non-GI system diseases as a cause for abdominal pain, the diagnosis must be further refined to rule out small bowel pathology. Acute gastroenteritis, Henoch-Schonlein purpura, and subacute/chronic gastrointestinal (GI) problems, can be investigated by questioning the chronicity of the symptoms (regional ileitis), the involvement of family members with similar symptoms (acute gastroenteritis), and the presence of blood in the stools (intussusception and intestinal infection) (2,4).

Children with appendicitis often have aggravation of pain with movement and thus we see that children tend to lie motionless and often say that the pain is worsened by walking. Another common presentation of acute appendicitis is an infant with their right hip flexed since the relaxation and extension of the hip can reproduce pain. A rare exception to the pattern of immobility is the involvement of the right ureter in retrocecal appendicitis as this can produce a colicky pain that may be alleviated with movement.

As appendiceal inflammation progresses, the protective mechanism of the bowel causes it to become less active and bowel sounds are diminished until the abdomen becomes quiet with frank peritonitis. Normal or hyperactive bowel sounds should cast doubt on a diagnosis of appendicitis (4). While the examiner is evaluating bowel sounds, he or she should listen to the lower lobes of the chest since pneumonia of the lower lobes can cause inflammation of the lower thoracic dermatomes and be interpreted as abdominal pain.

Before palpating the abdomen, it is recommended to ask the patient to point with one finger to the location of abdominal pain as accurately as they can. The examiner should gently palpate in a counterclockwise fashion starting in the left lower quadrant (LLQ) towards the RLQ with the knees and hips in flexion to relax the abdominal muscles. If the examiner starts in the area of most reported pain, the child will likely start crying and make further evaluation difficult. The stiffening of the abdominal muscles to restrict deeper palpation is called voluntary guarding and is an important observation when limited to the RLQ. Further inflammation of the serosal surface leads to involuntary guarding or spasm indicating peritonitis. Examination of the psoas muscles (by right hip extension or raising the straight leg against resistance, known as the psoas sign) as well as the obturator muscle (demonstrated by passive internal rotation of the right thigh, known as the obturator sign) can elicit pain which would point towards a retrocecal appendicitis.

The physical examination portion should conclude with an evaluation of groin tenderness to check for inguinal hernias or iliac adenitis as the cause for abdominal pain. The male genitalia should be examined to confirm the absence of testicular pain or swelling, which young patients often do not reveal to their parents. The utility of rectal examination has been questioned but it may be indicated in appendiceal perforation or when a pelvic abscess is suspected.

In most cases, diagnosis of acute appendicitis can be highly suspected with an accurate history and comprehensive exam. Elevated WBC with a neutrophilia has often been used as evidence of appendicitis although sensitivity of these values has ranged between 52% to 96% with 5% of appendicitis displaying normal lab values (1). Microscopic blood and white cells in the urine can be evidence of an inflamed appendix overlying the right ureter causing transmural inflammation. Diagnosing this as a urinary tract infection, can delay the diagnosis and treatment of appendicitis. An abnormal UA with the absence of dysuria or renal colic could support a diagnosis of appendicitis.

Screening scores have been developed to assist in the diagnosis of acute appendicitis. The Alvarado Score, Pediatric Appendicitis Score (PAS), and Appendicitis Inflammatory Response Score (AIRS) are all validated measures in pediatric populations to assess the likelihood of appendicitis (5,6). These tools use a history and physical exam paired with a CBC to assess the probability of appendicitis. The AIRS includes a C-reactive protein and published likelihood ratios validate it as the most accurate screening tool in pediatric patients (2).

Ultrasound (US) examination of the appendix is widely available and it avoids radiation exposure associated with computed tomography (CT) scans. US as a diagnostic tool can be powerful when used by trained technicians as meta-analysis of ED physicians has identified sensitivity and specificity of US at 91% and 97% respectively (7). Other reviews have identified sensitivity and specificity rates as low as 74% and 88% with further decreases in accuracy that were highly correlated with the operator’s familiarity with US (8). Published studies on the diagnostic accuracy of ultrasound are frequently performed in specialized centers (e.g., a pediatric emergency department with pediatric ultrasonography technicians and pediatric radiologists). Thus, these accuracy numbers should not be expected in centers without the same specialized personnel that were available in the published studies. If the appendix can be reliably visualized on ultrasound, the demonstration of an appendix greater than 7mm in anteroposterior diameter, presence of an appendicolith, thickening of the mesentery or appendiceal wall, and hyperemia on doppler are findings consistent with acute appendicitis (9).

A recent meta-analysis examining the accuracy of CT scans to diagnose appendicitis in children determined sensitivity and specificity values of 96.2% and 94.6% (9). Since CT scans have significant radiation exposure and ultrasound has comparable diagnostic accuracy when performed in referral centers, the American College of Radiology recommends US as the first-line diagnostic study (10,11).

Magnetic resonance imaging (MRI) has emerged as a comparable if not superior imaging modality to CT in the identification of appendicitis (12,13). Because of its accuracy, lower reliance on operator expertise, and lack of radiation exposure, some practices have opted to use MRI as first-line imaging modality (14). Issues such as availability and the need to sedate young patients limit its current use; however, MRI is evolving as a technology and it is very likely that we can anticipate that in the future, MRI will be faster, which will eliminate the need for sedation, and it will become more available.

The use of plain film radiography is not a recommended diagnostic modality for diagnosing appendicitis unless trying to rule out other causes of acute abdominal pain (1). Bowel obstruction or perforation could be identified with an abdominal X-ray but has little success in identifying uncomplicated acute appendicitis.

The single most important observation which places acute appendicitis at the head of a list of differential diagnoses is right lower quadrant tenderness. Tenderness should be constant and often worsened by movement or palpation. Inconsistent or generalized tenderness casts doubt on the diagnosis of appendicitis.

Mesenteric adenitis is a common non-surgical entity that often mimics acute appendicitis. Unless another treatable entity is identified, it is generally noted but not treated. Ultrasound imaging will often note enlarged lymph nodes with a normal appendix in such cases (15).

Children with appendicitis often have not eaten for a day or so and have likely vomited thus making dehydration an important consideration (2). While in the emergency department, pending surgical evaluation, a rapid infusion of isonatremic fluid is often required to restore a euvolemic state (3). Those patients with peritonitis should be encouraged to take deep breaths to prevent atelectasis and pneumonia since abdominal pain and distention cause elevation and splinting of the diaphragm leading to inadequate lung expansion and retention of secretions.

Acute appendicitis is most often treated with appendectomy. The technicalities of surgical approach and post-operative management largely lack consensus. A meta-analysis of laparoscopic vs. open appendectomy surgeries performed on children and adults found reduced risk of wound infection, fewer postoperative complications, and shortened postoperative stays with faster returns to activities in laparoscopic procedures although these were associated with longer operative times (16). It was once thought open surgery was preferred to laparoscopic surgery in the setting of complicated perforation but newer data suggests there are no significant differences in perioperative complications and outcomes (4).

Antibiotic treatment is beneficial in the management of appendicitis, but the regimen and duration of antibiotic therapy is a subject of controversy. Some emerging evidence has shown that antibiotic monotherapy without surgical intervention in the setting of uncomplicated appendicitis can be successful; however, there is a risk of appendicitis recurrence requiring appendectomy within one year of antibiotic therapy. Appendicitis with an associated fecalith was found to be ineffectively treated with antibiotics alone (4,17). If perforation is suspected because of the severity of symptoms and the presence of peritonitis or evidence of perforation on CT scan, preoperative antibiotics should be administered and continued post-operatively.

Establishing the diagnosis of appendicitis can be difficult, especially in cases that present atypically. A delayed diagnosis is often associated with poorer outcomes, patient dissatisfaction, and medical legal liability concerns. Ideally patients/parents should be aware of signs and symptoms that increase the probability of appendicitis that should prompt a return for medical reevaluation. A standardized abdominal pain instruction sheet can be helpful, and actively teaching the patient and parents about right lower quadrant pain, difficulty walking, and other symptoms/signs of appendicitis can help patients and parents to better understand when they need to return to the ED for reevaluation.

1. If appendicitis is clinically suspected, which of the following is the best initial diagnostic imaging study?
   a. X-ray
   b. Ultrasound
   c. CT scan
   d. MRI

2. A child presents to the ED with a diagnosis of uncomplicated acute appendicitis. The parents are declining surgery and asking for alternative treatments. What is a correct response?
   a. This is a life threatening emergency and there is no alternative to surgery
   b. Your child will likely be fine on supportive measures and should be able to leave the ED in a few hours
   c. We will give your child IV fluids and then you can go home when their vitals are stable
   d. In the absence of surgery, it is recommended that your child start on antibiotics and be hospitalized until they improve

3. Which of the following is NOT TRUE regarding the management of appendicitis?
   a. Antibiotics should be started regardless if patient will be taken to surgery
   b. Appendicitis pain classically starts midline and then migrates to McBurneys point
   c. Elevated WBC in the setting of suspected appendicitis is a definitive diagnostic finding
   d. Developing secondary pneumonia is a risk associated with appendicitis

Related x-rays
Ruptured appendix case: Yamamoto LG. Abdominal Pain and the Peritoneal Fat Margins. In: Yamamoto LG, Inaba AS, DiMauro R (eds). Radiology Cases In Pediatric Emergency Medicine, 1995, volume 3, case 19. Available online at:

Appendicitis case: Yamamoto LG. Post-Surgical Febrile Seizure and Vomiting. In: Yamamoto LG, Inaba AS, DiMauro R (eds). Radiology Cases In Pediatric Emergency Medicine, 1996, volume 4, case 10. Available online at:

Appendicoliths. Yamamoto LG, Goto CS. Appendicoliths. In: Yamamoto LG, Inaba AS, DiMauro R (eds). Radiology Cases In Pediatric Emergency Medicine, 1999, volume 6, case 18. Available online at:

1. Dunn, J. Chapter 100. Appendicitis. In: Coran AG, Caldamone A, Adzick NS, Krummel TM, Laberge J-M, Shamberger R (eds). Pediatric Surgery, 7th edition, 2014. Saunders, Philadelphia. pp: 1255-1263.
2. Stringer MD. Acute Appendicitis. J Paediatr Child Health. 2017;53(11):1071–1076.
3.Singh JP, Mariadason JG. Role of the Faecolith in Modern-Day Appendicitis. Ann R Coll Surg Engl. 2013;95(1):48–51.
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5. Kollár D, McCartan DP, Bourke M, et al. Predicting Acute Appendicitis? A Comparison of the Alvarado Score, the Appendicitis Inflammatory Response Score and Clinical Assessment. World J Surg. 2014;39(1):104–109.
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Answers to questions
1. b. Ultrasound is the recommended first line diagnostic tool for evaluation of appendicitis. CT offers excellent sensitivity and specificity for appendicitis and can be used in the event of equivocal ultrasound results but it should not be the first line study. MRI is generally not recommended since the exam takes a long time, its availability is limited, and young children must often be sedated.. Plain film x-ray is not a recommended first line diagnostic since it has relatively poor sensitivity and specificity for diagnosing appendicitis but has some utility in ruling out perforation. The widespread availability and speed of ultrasound makes them the preferred modality.
2. d. Acute uncomplicated appendicitis is not necessarily a surgical emergency although appendicitis complicated by abscess or perforation certainly is. It would also not be recommended to discharge the child home since uncomplicated appendicitis is likely to evolve into a more serious peritonitis if the appendix is perforated. Evidence has shown that appendicitis can be managed with antibiotics however it is possible that this may not fully resolve the appendicitis and there is some risk of recurrence.
3. c. Elevated WBC alone is not specific or sensitive enough to diagnose appendicitis.

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