Introduction
Background
The appendix is a blind-ending tubular structure arising from the cecum. Appendicitis results from an acute inflammation of the appendix and creates the most common abdominal surgical emergency.1,2
A diagnosis of acute appendicitis is usually made on the basis of a patient's clinical history in conjunction with physical examination and laboratory studies. Because the surgical aim is to operate early—before appendiceal rupture and peritonitis develop—patients who present with typical findings undergo immediate surgery without radiologic evaluation. However, such imaging is advisable in patients with atypical symptoms, which can occur in infants and small children, the elderly, and young women.
Perforated appendicitis with abscess; computed tomography scan. Note the appendicolith (arrow) and air within the abscess. The terminal ileum lies anterior to the appendiceal abscess, and inflammatory change is noted in its wall, which appears thickened (open arrow).
Atypical presentation of appendicitis in a young woman; computed tomography scan. The patient presented with an elevated white blood cell count and right upper quadrant pain. Left, there is pericholecystic fluid and free fluid in the right paracolic gutter, which is caused by retrocecal appendicitis. Right, the appendix, observed in axial section, has an increased diameter and an enhancing thickened wall.
For excellent patient education resources, visit eMedicine's Esophagus, Stomach, and Intestine Center. Also, see eMedicine's patient education articles, Appendicitis, Abdominal Pain in Adults, and Abdominal Pain in Children.
Pathophysiology
Obstruction of the narrow appendiceal lumen is the primary cause of appendicitis and may often be secondary to impacted fecal material or hyperplasia of the submucosal lymphoid follicles, which is associated with respiratory disease, infectious mononucleosis, and gastroenteritis. Fecaliths result from the inspissation of fecal material and inorganic salts within the appendiceal lumen, are the most common causes of obstruction, and are present in 11-52% of patients with acute appendicitis. Appendiceal calculi are rarely observed, and their presence is usually associated with perforating appendicitis. Appendiceal lumenal obstruction may also be secondary to strictures, parasitic infection, the presence of foreign bodies, Crohn disease, primary or secondary metastatic cancer, carcinoid syndrome, kinks, and adhesions.3
The stages of appendicitis
- Early stage of appendicitis: Obstruction of the appendiceal lumen leads to mucosal edema, mucosal ulceration, bacterial diapedesis, appendiceal distention due to accumulated fluid, and increasing intraluminal pressure. The visceral afferent nerve fibers are stimulated, and the patient perceives mild visceral periumbilical or epigastric pain, which usually lasts 4-6 hours.
- Suppurative appendicitis: Increasing intraluminal pressures eventually exceed capillary perfusion pressure, which is associated with obstructed lymphatic and venous drainage and allows bacterial and inflammatory fluid invasion of the tense appendiceal wall. Transmural spread of bacteria causes acute suppurative appendicitis. When the inflamed serosa of the appendix comes in contact with the parietal peritoneum, patients typically experience the classic shift of pain from the periumbilicus to the right lower abdominal quadrant (RLQ), which is continuous and more severe than the early visceral pain.
- Gangrenous appendicitis: Intramural venous and arterial thromboses ensue, resulting in gangrenous appendicitis.
- Perforated appendicitis: Persisting tissue ischemia results in appendiceal infarction and perforation. Perforation can cause localized or generalized peritonitis.
- Phlegmonous appendicitis or abscess: An inflamed or perforated appendix can be walled off by the adjacent greater omentum or small-bowel loops, resulting in phlegmonous appendicitis or focal abscess.
Rare types of appendicitis include the following:
- Spontaneously resolving appendicitis: If the obstruction of the appendiceal lumen is relieved, acute appendicitis may resolve spontaneously.4,5 This occurs if the cause of the symptoms is lymphoid hyperplasia or when a fecalith is expelled from the lumen.
- Recurrent appendicitis: The incidence of recurrent appendicitis is 10%. The diagnosis is accepted as such if the patient underwent similar occurrences of RLQ pain at different times that, after appendectomy, were histopathologically proven to be the result of an inflamed appendix.
- Chronic appendicitis: Chronic appendicitis occurs with an incidence of 1% and is defined by the following: (1) the patient has a history of RLQ pain of at least 3 weeks’ duration without an alternative diagnosis; (2) after appendectomy, the patient experiences complete relief of symptoms; (3) histopathologically, the symptoms were proven to be the result of chronic active inflammation of the appendiceal wall or fibrosis of the appendix.
The incidence of appendicitis is higher in more affluent countries that have a prevalence of low-fiber diets. Low-fiber diets change the bacterial flora, increasing stool viscosity, bowel transit time, and intraluminal pressure, which encourage the formation of fecaliths. These diets contribute to low-residue stool, which can become impacted within the appendiceal lumen.
Frequency
United States
In the United States, 250,000 cases of appendicitis are reported annually, representing 1 million patient-days of admission. The incidence of acute appendicitis has been declining steadily since the late 1940s, and the current annual incidence is 10 cases per 100,000 population. The overall lifetime risk of developing appendicitis is approximately 7%. Some familial predisposition exists.
International
Appendicitis appears to be a disease of prosperous Western nations; the incidence of appendicitis is higher in more affluent countries that have prevalent low-fiber diets.
Mortality/Morbidity
Acute appendicitis is the most common reason for emergency abdominal surgery. Appendectomy carries a complication rate of 4-15%, as well as associated costs and the discomfort of hospitalization and surgery. Therefore, the goal of the surgeon is to make an accurate diagnosis as early as possible. Delayed diagnosis and treatment account for much of the mortality and morbidity associated with appendicitis.
The overall accuracy for diagnosing acute appendicitis is approximately 80%, which corresponds to a mean false-negative appendectomy rate of 20%. Diagnostic accuracy varies by sex, with a range of 78-92% in male patients and 58-85% in female patients.
- False-negative and -positive rates associated with appendectomy reflect the diagnostic difficulty encountered in differentiating appendicitis from other acute abdominal conditions. Appendicitis may be extremely difficult to diagnose in women of childbearing age, because symptoms of acute gynecologic conditions, such as pelvic inflammatory disease, may manifest similarly. This problem results in false-positive appendectomy rates as high as 47% in female patients aged 10-39 years. Spiral computed tomography (CT) scanning and ultrasonography (US) may lower the rate of false–negative appendectomy diagnosis and reduce the rate of perforation by shortening in-hospital delay in treatment.
- The mortality rate for acute appendicitis is less than 1 per 100,000 persons (0.2-0.8%). The mortality rate in children ranges from 0.1-1%; in patients older than 70 years, the rate rises above 20%.
- Appendiceal perforation is associated with increased morbidity and mortality compared with nonperforating appendicitis. The mortality risk of acute but not gangrenous appendicitis is less than 0.1%, but the risk rises to 0.6% in gangrenous appendicitis. The rate of perforation varies from 16-40%, with a higher frequency occurring in younger age groups (40-57%) and in patients older than 50 years (55-70%), in whom misdiagnosis and delayed diagnosis are common. Complications occur in 1-5% of patients with appendicitis, and postoperative wound infections account for almost one third of the associated morbidity.
Sex
The male-to-female sex ratio is 3:2 in teenagers and young adults. By the time patients reach their mid-30s, males and females have similar incidence rates.
Age
Appendicitis occurs in all age groups but is rare in infants; the incidence becomes increasingly common in childhood, reaching a peak incidence in the late teenage years and early 20s. The mean age when appendicitis occurs in the pediatric population is 6-10 years.
- Younger children have a higher rate of perforation, with reported rates of 50-85%.
- Lymphoid hyperplasia is observed more often among infants and adults and is responsible for the increased incidence of appendicitis in these age groups.
Anatomy
The appendix vermiformis is a thin, wormlike, tubular organ that is located at the inferior part of the cecum. In adults, a normal vermiform appendix varies in length from 5-35 cm (average 8 cm).
The appendix has no fixed position. It originates 1.7-2.5 cm below the terminal ileum, either in a dorsomedial location (most common) from the cecal fundus, directly beside the ileal orifice, or as a funnel-shaped opening (2-3% of patients). The appendix has a retroperitoneal location in 65% of patients and may descend into the iliac fossa in 31%. The difference in appendiceal position considerably changes clinical findings.
Appendiceal congenital disorders are extremely rare but occasionally reported (eg, agenesis, duplication, triplication).
The appendix has its own mesentery, which arises from a peritoneal extension that extends from the terminal ileum to the medial aspect of the cecum and appendix. This mesenteric fold contains the appendicular artery, which is a terminal branch of the ileocolic artery, and runs adjacent to the appendicular wall. Venous drainage is via the ileocolic veins and the right colic vein into the portal vein; lymphatic drainage occurs via the ileocolic nodes along the course of the superior mesenteric artery to the celiac nodes and cisterna chyli.
The appendix is contained within the visceral peritoneum that forms the serosa, and its exterior layer comprises longitudinal muscle with a deeper, interior circular muscle layer. Beneath these layers lies the submucosal layer, which contains lymphoepithelial tissue. The mucosa consists of columnar epithelium with few glandular elements and neuroendocrine argentaffin cells.
Presentation
A diagnosis of appendicitis can usually be made on the basis of the patient’s clinical history and physical examination. Understanding the typical clinical manifestations of appendicitis is important and helps clinicians to make an early and accurate diagnosis before appendiceal perforation occurs.6
Symptoms of appendicitis may take 4-48 hours to develop. The classic history of lack of appetite and periumbilical pain that is followed by nausea, RLQ pain, and vomiting occurs in only 50-60% of patients; indeed, any combination of these symptoms may occur.
- The patient's pain is typically colicky and is initially located periumbilically or epigastrically. The pain subsequently shifts to the RLQ (50%), where it becomes progressively more severe. The migration of pain is the most discriminating historical feature, with a sensitivity and specificity of approximately 80%.
- Nausea (61-92%), vomiting, anorexia (74-78%), and low-grade fever are common. When vomiting occurs, it almost always follows the onset of pain.
- Diarrhea or constipation is observed in 18% of patients.
- Abdominal rebound tenderness (96%), pain on percussion, rigidity, and guarding are specific physical findings of acute appendicitis.
- RLQ pain with palpation of the left lower quadrant (Rovsing sign), RLQ pain with hyperextension of the right hip (psoas sign), and RLQ pain with internal rotation of the flexed right hip (obturator sign) are rarely present with acute appendicitis.
- Leukocytosis (>10,000/mm3) is observed in 80% of patients with acute appendicitis. However, elevated levels can be noted with other conditions, and normal white blood cell (WBC) levels are often present with appendicitis. Neutrophilia is also observed (95%).
- It has been suggested that high levels of C-reactive protein (>0.8 mg/dL) in association with leukocytosis and neutrophilia are the most sensitive laboratory findings for appendicitis, with a sensitivity of approximately 97-100%.7,8 Therefore, the probability of acute appendicitis is low in the absence of these 3 laboratory findings.
- A urine test may be performed to exclude urinary tract infection as the cause of the patient’s symptoms.
Suppurative appendicitis; transverse view, color Doppler ultrasound image. Circumferential colors are observed in the wall of the inflamed appendix (arrows), a strong indicator of acute appendicitis.
Atypical presentation of appendicitis in a young woman; computed tomography scan. The patient presented with an elevated white blood cell count and right upper quadrant pain. Left, there is pericholecystic fluid and free fluid in the right paracolic gutter, which is caused by retrocecal appendicitis. Right, the appendix, observed in axial section, has an increased diameter and an enhancing thickened wall.
Radiologic examination can reduce the number of misdiagnoses and unnecessary laparotomies, as well as help in the treatment of patients with appendiceal abscesses and those with postoperative complications.
Preferred Examination
Controversy exists as to whether imaging is required in patients with the classic history and physical findings of acute appendicitis. Opinion varies as to whether these modalities should be performed in all patients with suggested appendicitis or if radiology should be reserved for select patients with atypical or confusing clinical presentations.
Helical and multidetector CT scanning and graded-compression Doppler US are powerful imaging methods that substantially improve diagnostic accuracy in patients with clinically equivocal appendicitis (see Images 1 and 3).9
Suppurative appendicitis; transverse view, color Doppler ultrasound image. Circumferential colors are observed in the wall of the inflamed appendix (arrows), a strong indicator of acute appendicitis.
Appendicitis in a young physician with appendicitis; computed tomography (CT) study. Intravenous (IV) contrast was administered to the patient, who had gram-negative sepsis but no abdominal pain on examination. Left, an inconclusive CT scan after administration of oral contrast but no IV contrast. Right, a repeat CT scan study following administration of IV contrast demonstrates the thickened, enhanced appendiceal wall and periappendiceal changes. The retrocecal location of the appendix may have attenuated abdominal symptoms.
Before the 1980s, abdominal radiographs and barium enema were the primary radiologic methods used in the diagnosis of acute appendicitis. On plain radiographic films, the presence of an appendicolith is the most specific sign, but it is rarely observed. On barium enema examination, nonfilling or incomplete filling of the appendix indicates appendiceal inflammation.
Continuous improvements in imaging technology, technique, and interpretation that have been achieved over the past 15 years have substantially increased the accuracy of imaging methods. Since 1986, US and, after the 1990s, CT scanning have gained acceptance as the primary imaging techniques for acute appendicitis by virtue of their ability to directly image the appendix, adjacent fat, and gut.
Graded-compression US of the RLQ has been shown to be a useful examination because of this technique's safety and high accuracy (approximately 90%) in the diagnosis of acute appendicitis. Advantages of US include lack of radiation exposure, noninvasiveness, short acquisition time, and the potential for diagnosis of other causes of abdominal pain, particularly in the subset of patients who are women of childbearing age. Several authorssuggest that US should be the first imaging method used in pregnant women and pediatric patients because x-ray exposure is especially undesirable in these groups.
Contrast-enhanced, thin-section (0.5 mm) CT scanning has become the preferred imaging technique in the diagnosis of acute appendicitis and its complications, with a high diagnostic accuracy of 95-98% (see Image 3). The literature suggests that limited helical CT scanning with rectal contrast is a highly accurate, time-efficient, cost-effective way to evaluate adult patients with equivocal presentations for appendicitis. CT scanning is particularly preferred in patients in whom appendiceal perforation is suspected, because the diagnostic accuracy remains high and because CT scanning is useful for characterizing periappendiceal inflammatory masses.
Other advanced radiologic examinations, such as magnetic resonance imaging (MRI), scintigraphy, and color Doppler US, have been used in the diagnosis of acute appendicitis (see Images 1 and 3-5), with a diagnostic accuracy of approximately 91-95%. Currently, no practical role exists for MRI and scintigraphy in acute appendicitis. Advantages of MRI include better visualization of abnormal appendices and adjacent inflammatory processes, visualization of the appendix in an atypical location, delineation of pathology, operator independence, and ease of examination of patients who are obese. MRI, similar to enhanced CT scanning, can demonstrate the extent of inflammatory infiltration (see Image 6).10
Acute suppurative appendicitis in a 15-year-old boy; contrast-enhanced, fat-suppressed, T1-weighted, spin-echo coronal magnetic resonance image. A markedly enhanced and thickened inflamed appendix (arrows) with pericecal enhancement due to the extent of inflammation is shown.
Acute suppurative appendicitis in a 27-year-old woman; scintigraphy study. Pathologic accumulation of technetium-99m human immunoglobulin on the right iliac fossa is observed at 4 hours.
Periappendiceal abscess; contrast-enhanced, fat-suppressed, T1-weighted, spin-echo coronal magnetic resonance image. Fluid collections (long arrows) and a markedly enhanced pericecal area (short arrows) are shown. b = bladder; c = cecum.
The decision to obtain US or CT scan studies depends on institutional preference and the available user expertise, although patient age, sex, and body habitus are important influencing factors. US and CT scanning have similar diagnostic value for detecting an alternative diagnosis in a patient in whom acute appendicitis is suspected. Balthazar et al showed that CT scanning is superior to US in the diagnosis of acute appendicitis11 ; however, US is rapid, safe, inexpensive, and noninvasive, and it requires no contrast material or patient preparation.
At the author's institution, graded-compression US and color and power Doppler US techniques are routinely used in the diagnosis of acute appendicitis, with a diagnostic accuracy of approximately 95-100% in all patients with suspected acute appendicitis. CT scans or MRIs are complementary to US and are used for patients in whom the US findings are equivocal or suboptimal.
Limitations of Techniques
Abdominal radiographs are normal in many patients with acute appendicitis and should not be obtained routinely. An appendicolith is the most specific sign on plain radiographic films, but it is observed in only 10% of patients with appendicitis. Disadvantages of barium enema include a high incidence of nondiagnostic examinations, radiation exposure, insufficient sensitivity, and invasiveness.A significant disadvantage of US is that it is operator dependent. Intestinal peristalsis, pulsations of the iliac artery (when it is close to the appendix), deep respiration in noncooperative patients, and difficulty maintaining the probe at the same location for a long time are disadvantages of color Doppler US in detecting increased vascularity of the appendix.
Disadvantages of CT scanning include radiation exposure, the potential for anaphylactoid reaction if intravenous (IV) contrast is used, lengthy preparation time if oral contrast is used, and patient discomfort if rectal contrast is used.
Disadvantages of MRI include high cost, use of IV contrast, the requirement that patients fully cooperate, difficulty with patients who are claustrophobic, the inability to observe an appendicolith in the lumen (an important finding in acute appendicitis), and the inability to differentiate between gas and an appendicolith in the perforation site.
Disadvantages of radionuclide scanning include long acquisition times (approximately 5 h) and the lack of availability of this modality.
Differential Diagnoses
| Cholecystitis, Acute | Mesenteric Adenitis |
| Cholelithiasis | Nephrolithiasis/Urolithiasis |
| Colon, Diverticulitis | Ovarian Torsion |
| Endometrioma/Endometriosis | Pelvic Inflammatory Disease/Tubo-ovarian
Abscess |
Other Problems to Be Considered
Crohn disease
Appendagitis
Diverticulitis
Segmental omental infarction
Meckel diverticulitis
Perforated peptic ulcer
Ileal or cecal perforation
Tuberculous ileitis
Yersinial ileitis
Omental torsion
Familial Mediterranean fever
More on Appendicitis |
 Overview: Appendicitis |
| Imaging: Appendicitis |
| Follow-up: Appendicitis |
| Multimedia: Appendicitis |
| References |
| Further Reading |
| Next Page » |
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Further Reading
Related eMedicine topics
Appendicitis (from General Surgery)
Appendicitis (from Emergency Medicine)
Appendicitis, Acute
Pediatrics, Appendicitis
Appendicitis: Surgical Perspective
Clinical guidelines
ACR Appropriateness Criteria Right Lower Quadrant Pain
Clinical trials
CT Scan Using IV Contrast Alone for Pediatric Appendicitis
Hyperbilirubinemia in Acute Appendicitis as a Predictor of Perforation
Keywords
appendicitis, acute appendicitis, inflammation of the appendix, appendicolith, arrowhead sign, acute abdomen
