Acute appendicitis in adults: Diagnostic evaluation

INTRODUCTION — Appendicitis is common and is seen in up to 1 in 10 individuals over a lifetime. (See "Acute appendicitis in adults: Clinical manifestations and differential diagnosis", section on 'Epidemiology'.)

The evaluation of patients with suspected appendicitis is driven by the goal of identifying all patients presenting with acute appendicitis as early in their clinical course as possible while minimizing the nontherapeutic laparoscopy/laparotomy rate. Missed diagnosis of appendicitis, especially when perforated, can result in severely adverse patient outcomes, while nontherapeutic operations incur surgical morbidity without treating the underlying condition.

This topic reviews the diagnostic evaluation of suspected appendicitis in nonpregnant adults, incorporating the clinical evaluation, laboratory tests, and imaging examinations. Diagnosis of appendicitis in children and pregnant women is discussed separately, as are the pathogenesis, clinical manifestations, differential diagnosis, and management. (See "Acute appendicitis in children: Clinical manifestations and diagnosis" and "Acute appendicitis in pregnancy" and "Acute appendicitis in adults: Clinical manifestations and differential diagnosis" and "Management of acute appendicitis in adults".)

CLINICAL AND LABORATORY EVALUATION — Initial evaluation consists of clinical assessment (ie, history and physical examination) and laboratory evaluation, which is standardized in most emergency departments. Although clinical and laboratory parameters may be suggestive, none are sufficiently sensitive or specific to exclude or diagnose appendicitis [1].

Clinical evaluation — The diagnostic accuracy of the clinical evaluation for acute appendicitis depends on the experience of the examining clinician [2-7]. The patient presenting with acute abdominal pain should undergo a thorough physical examination, including a digital rectal examination. Women should undergo a pelvic examination. Women of reproductive age should be queried regarding the possibility of pregnancy.

●Clinical symptoms and signs suggestive of appendicitis include a history of central abdominal pain migrating to the right lower quadrant, anorexia, fever, and nausea/vomiting.

●On examination, right lower quadrant tenderness, along with classical signs of peritoneal irritation (eg, rebound tenderness, guarding, rigidity, referred pain), may be present. Other signs (eg, the psoas or obturator signs) may help the clinician localize the inflamed appendix [8,9]. This is discussed in more detail separately. (See "Acute appendicitis in adults: Clinical manifestations and differential diagnosis", section on 'Clinical manifestations'.)

Importantly, a high index of suspicion for the diagnosis of appendicitis should be maintained when evaluating older and frail patients, who can present with nonclassical symptoms (eg, generalized abdominal pain, lack of leukocytosis).

Laboratory tests — The laboratory evaluation of patients with suspected appendicitis should include:

●White blood cell (WBC) count with differential

●Serum C-reactive protein (CRP)

●Pregnancy test in women of childbearing age

The diagnostic performance of WBC and CRP is moderate individually, but sensitivity improves substantially in combination (table 1) [10]. Some limited evidence also suggests that repeated laboratory evaluation may boost the sensitivity in detecting appendicitis, especially in patients who present early [11]. However, no WBC count or CRP level can safely and sufficiently confirm or exclude the suspected diagnosis of acute appendicitis. As an example, one retrospective multicenter study of 1024 adults with suspected appendicitis reported that with a disease prevalence of 57 percent (580 diagnosed with appendicitis), an abnormal cutoff value of WBC >10 x 10⁹/L or CRP >10 mg/L yielded a positive predictive value (PPV) of 61.5 (95% CI 58.4-64.7) and a negative predictive value (NPV) of 88.1 (95% CI 81.8-94.4) [12].

Others have investigated the utility of neutrophil-to-lymphocyte ratio (NLR). A meta-analysis of 17 observational studies involving close to 9000 patients of all ages (some pregnant) found that NLR, at a cutoff value of 4.7, predicted appendicitis with a sensitivity of 89 percent and specificity of 91 percent (area under curve [AUC] 0.96). NLR at a cutoff value of 8.8, on the other hand, predicted complicated appendicitis with a sensitivity of 77 percent and specificity of 100 percent (AUC 0.91) [13].

Although mild elevations in serum bilirubin (total bilirubin >1.0 mg/dL) have been noted to be a marker for appendiceal perforation with a sensitivity of 70 percent and specificity of 86 percent [14], the test is not discriminatory and is generally not helpful in the evaluation of patients suspected of acute appendicitis.

DIAGNOSTIC EVALUATION WHEN CT IS AVAILABLE — When available, we suggest performing contrast-enhanced abdominopelvic computed tomography (CT) to diagnose appendicitis in nonpregnant adult patients. Abdominal ultrasound or magnet resonance imaging (MRI) may be performed in young women (<30) who are particularly concerned about radiation risks (algorithm 1).

Imaging for appendicitis in children and pregnant women is discussed elsewhere. (See "Acute appendicitis in children: Diagnostic imaging" and "Acute appendicitis in pregnancy", section on 'Imaging'.)

Standard versus selective imaging — The approach to imaging for suspected appendicitis varies greatly by geography [15]. In some cases, advanced imaging modalities (ie, CT or MRI) are simply not available [16]; in other cases, local tradition or practice precludes standard imaging [17].

When available, we suggest routine imaging for patients suspected of appendicitis for the following reasons:

●The most compelling one is that surgery after standard imaging reduces negative appendectomy rates compared with surgery without imaging [18-20]. Studies show that the addition of CT or ultrasound to the clinical evaluation of suspected appendicitis is associated with a reduction in negative appendectomy rate without an associated increase in perforation rate [21-26]. In a retrospective study of 19,327 patients at 55 hospitals in Washington state over six years, the odds of negative appendectomy for patients not imaged were 3.7 times higher than those who received imaging (95% CI 3-4.4) [26]. The benefit of imaging was independent of age, sex, and white blood cell count. Appendiceal perforation rate was the same between patients who were and were not imaged (18.8 versus 15.6 percent). In a comparative study of two healthcare systems, the negative appendectomy rate in Britain (selective imaging) was much higher (20.6 versus 3.2 percent) than that in the Netherlands (standard imaging) [18].

●For patients who present with abdominal pain but do not have appendicitis, imaging is still needed in most cases to reach an alternative diagnosis [27].

●For patients who have appendicitis, imaging is required to differentiate between complicated and uncomplicated appendicitis as only the latter is eligible for nonoperative/antibiotic-only therapy. (See "Management of acute appendicitis in adults", section on 'Nonoperative management'.)

●There is also evidence that routine imaging may be cost effective [28].

Our recommendation for routine imaging is consistent with the latest algorithms from the World Society of Emergency Surgery [29], European Association of Endoscopic Surgery [30], and Eastern Association for the Surgery of Trauma [31]. More importantly, the American College of Emergency Physicians clinical policy states, "In adult patients, because of insufficient data, do not use clinical prediction rules to identify patients for whom no advanced imaging is required" [1]. Thus, given that most cases of appendicitis are diagnosed in the emergency department, routine imaging for appendicitis is likely a fait accompli in the United States.

Adult women are more than twice as likely as men (20 versus 10 percent) to have a nontherapeutic appendectomy for suspected acute appendicitis [21,32-37]. Imaging with CT can decrease the negative appendectomy rate in this population (21 versus 8 percent) [21]. Additionally, women of reproductive age can have gynecologic pathologies (eg, pelvic inflammatory disease, adnexal torsion) that mimic appendicitis clinically, which can be diagnosed by imaging studies even if they do not have appendicitis.

CT versus other image modalities — Imaging is used mainly to increase the specificity of the diagnostic evaluation for appendicitis and to decrease the negative appendectomy rate. We prefer CT to other imaging modalities for the following reasons (table 2) [38]:

●CT demonstrates the highest diagnostic accuracy and lowest rates of nondiagnostic examinations (ie, nonvisualization of the appendix) of all three image modalities. (See 'Computed tomography' below.)

●In resource-rich countries such as the United States, CT imaging is readily available in almost all emergency rooms and can be performed more expeditiously than abdominal ultrasound or MRI, even during afterhours. Thus, routine CT scanning of patients suspected of appendicitis may reduce the wait time of those patients in the emergency room.

●CT is better tolerated by the patient than ultrasound or MRI because it is quick and does not require compression (ultrasound) or the patient being in an enclosed space for a long time (MRI).

●CT is the imaging modality most commonly used in randomized trials establishing the efficacy of antibiotics-only treatment of early appendicitis. To quality for such treatment, patients need to have no perforation, phlegmon, or appendicolith, which is best determined by CT. (See "Management of acute appendicitis in adults", section on 'Nonoperative management'.)

Computed tomography — Abdominopelvic CT is the preferred imaging test for suspected appendicitis in adults (image 1 and image 2) [38].

CT demonstrates higher diagnostic accuracy than ultrasound or MRI (table 1). Other advantages of CT include less variability in diagnostic performance than ultrasound or MRI. CT demonstrates the lowest rates of nondiagnostic tests as the normal appendix is visualized in almost all cases (table 2). When compared with MRI, CT scanners and radiologist expertise are more readily available, and the examination is better tolerated by most patients. As CT imaging usually includes the abdomen and pelvis, the examination evaluates for other pathologies should the patient prove to not have appendicitis. The disadvantages of CT are patient exposure to ionizing radiation and iodinated contrast.

If available, low radiation dose image acquisition protocols should be used as they do not compromise diagnostic accuracy [39-42]. The estimated effective radiation dose of abdominopelvic CT is 8 to 10 mSv with the standard dose and 2 to 4 mSv with low-dose techniques [39]. To put these numbers into context, the effective dose from annual background radiation is 3.1 mSv and from plain abdominal radiography is 0.7 mSv.

Intravenous contrast administration is recommended in CT examinations performed for the diagnosis of appendicitis. Relative contraindications to contrast administration are [43]:

●Renal insufficiency (estimated glomerular filtration rate [eGFR] <30 mL/minute per 1.73 m²)

●History of hypersensitivity reaction to iodinated contrast

Noncontrast CT is an acceptable alternative if intravenous contrast is contraindicated. While reasonably high diagnostic accuracy is seen with noncontrast CT [44,45], intravenous contrast improves the examination value in other ways. In patients with appendiceal perforation where CT is used not only for diagnosis but also for treatment planning, contrast improves the delineation of the phlegmon or abscess. In one study, an alternative diagnosis was made in 42 percent (893 out of 2122) of patients without appendicitis, and the pathologic diagnosis was better characterized with intravenous contrast administration [46].

The use of oral or rectal contrast varies greatly among individual practices. The advantage of enteral contrast is that it distends the bowel, improving appendix visualization. Oral contrast administration delays scanning by one to two hours. Rectal contrast avoids this delay but is not well tolerated.

The imaging features of acute appendicitis on abdominopelvic CT are [47-49]:

●Enlarged appendiceal double-wall thickness (>6 mm)

●Appendiceal wall thickening (>2 mm)

●Periappendiceal fat stranding

●Appendiceal wall enhancement

●Appendicolith (seen in a minority of patients)

Diagnosing appendicitis based on a single criterion is not advised. As an example, while appendiceal diameter is larger in patients with appendicitis, more than 20 percent of patients without appendicitis have an appendiceal diameter >7 mm [50].

A meta-analysis of 72 studies on the ability of CT to diagnose appendicitis in adults reported a sensitivity of 95 percent (95% CI 95 to 97 percent) and a specificity of 96 percent (95% CI 93 to 97 percent). On subgroup analysis, diagnostic performance in older adults and in women of reproductive age was similar to that seen in the entire cohort, although specificity demonstrated wider confidence intervals [10]. CT performed with low-radiation-dose techniques demonstrates comparable diagnostic performance to standard-dose CT [51].

A 2019 Cochrane review of 64 studies found that CT had a summary sensitivity of 95 percent (95% CI 93 to 96 percent) and a summary specificity of 94 percent (95% CI 92 to 95 percent) when diagnosing appendicitis in adults [41]. In subgroup analysis, summary sensitivity was higher for CT with intravenous contrast, rectal contrast, and intravenous and oral contrast, but not oral contrast alone, compared with CT without contrast. Summary specificity did not improve with contrast enhancement. Compared with standard-dose CT, low-dose CT did not differ in performance.

A positive CT result indicates that treatment for appendicitis should be initiated, whereas a negative result indicates that a normal appendix has been visualized and appendicitis is highly unlikely as the diagnosis. Nonvisualization of the appendix (nondiagnostic result) occurs in 10 to 20 percent of examinations [52-54]. In the absence of a distinctly visualized appendix and secondary inflammatory changes, the incidence of acute appendicitis is low, but not zero [53,55]. Thus, surgical evaluation is indicated. (See 'Surgical evaluation or exploration' below.)

Ultrasound — In settings where CT is available, an abdominal ultrasound focused on the right lower quadrant may be performed in young women (<30) who are particularly concerned about radiation risks. In other settings where CT is not readily available, ultrasound may be the only imaging modality available to diagnose appendicitis (image 3 and image 4). (See 'Diagnostic evaluation when CT is not available' below.)

Advantages of ultrasound include the lack of ionizing radiation and intravenous contrast. Unlike CT or MRI, ultrasound can be performed at the bedside (table 2). However, an important disadvantage is that ultrasound demonstrates lower diagnostic accuracy than CT or MRI (table 1). The test performance is highly variable and depends on patient-specific (eg, body habitus, discomfort and alertness, appendix location relative to overlying bowel) and operator-specific (eg, experience) variables. Rates of indeterminate examinations are high, with 50 to 85 percent of normal appendices not visualized [56,57]. Finally, graded compression of the appendix, integral to the ultrasound examination, can cause significant patient discomfort in patients with appendicitis.

Imaging features of acute appendicitis on ultrasound include [58-60]:

●Noncompressible appendix with double-wall thickness diameter of >6 mm

●Focal pain over appendix with compression

●Appendicolith

●Increased echogenicity of inflamed periappendiceal fat

●Fluid in the right lower quadrant

A meta-analysis of 38 studies on the ability of ultrasound to diagnose appendicitis reported a sensitivity of 85 percent (95% CI 79 to 90 percent) and a specificity of 90 percent (95% CI 93 to 95 percent) [61,62].

A positive ultrasound result indicates that treatment for appendicitis should be initiated, whereas a negative result indicates that a normal appendix has been visualized and appendicitis is highly unlikely as the diagnosis. Importantly, unlike CT or MRI, a nondiagnostic ultrasound result does not have a high negative predictive value for appendicitis, and continued imaging evaluation is warranted (algorithm 1).

Magnetic resonance imaging — Similar to ultrasound, MRI of the abdomen is only used in the imaging evaluation of suspected appendicitis in the young women (<30) who are particularly concerned about radiation risks (image 5 and image 6) [38]. In this population, MRI may also be a substitute for CT to evaluate gynecologic diagnoses that remain in the differential diagnosis after the initial clinical evaluation and examination. However, lesser overall experience with MRI evaluation for acute appendicitis contributes to greater variability in its test performance characteristics compared with CT [63].

An advantage of MRI over CT is that it does not expose the patient to ionizing radiation or intravenous iodinated contrast (table 2). Intravenous contrast can be administered to improve accuracy if images without contrast prove nondiagnostic. Diagnostic accuracy is comparable to CT and is better than ultrasound (table 1). A Cochrane review of 58 studies on the MRI diagnosis of appendicitis reported a summary sensitivity of 0.95 percent (95% CI 0.94-0.97) and a summary specificity of 0.96 (95% CI 0.95-0.97). Sensitivity and specificity remained high on subgroup analysis for pregnant women (sensitivity 0.96 [95% CI 0.88-0.99]; specificity 0.97 [95% CI 0.95-0.98]); children (sensitivity 0.96 [95% CI 0.95-0.97]; specificity 0.96 [95% CI 0.92-0.98]); and adults (sensitivity 0.96 [95% CI 0.93-0.97]; specificity 0.93 [95% CI 0.80-0.98]), regardless of different scanning techniques and protocols [63].

Similar to CT, MRI allows for detection of alternative diagnoses should the patient not have appendicitis. However, the examination itself is less well tolerated than ultrasound or CT. The patient is usually required to lie still in a magnet for >10 minutes; this can be very uncomfortable for those who are claustrophobic, very young, or older and those with significant pain. Common relative contraindications include cardiac pacemakers and implanted metallic surgical hardware. (See "Patient evaluation for metallic or electrical implants, devices, or foreign bodies before magnetic resonance imaging", section on 'Assessing implants, devices, or foreign bodies for MRI' and "Patient evaluation for metallic or electrical implants, devices, or foreign bodies before magnetic resonance imaging".)

The rate of nondiagnostic examinations is higher than that reported with CT but lower than that with ultrasound, with 20 to 40 percent of normal appendices not visualized [64]. Similar to CT, in those patients where the appendix could not be visualized on MRI, and in the absence of signs of right lower quadrant inflammation, appendicitis is very unlikely but not impossible [65]. Thus, a surgical evaluation is indicated. (See 'Surgical evaluation or exploration' below.)

DIAGNOSTIC EVALUATION WHEN CT IS NOT AVAILABLE — When CT is not available, the diagnostic evaluation of suspected appendicitis must primarily rely on clinical and laboratory data. The use of a validated clinical scoring system may help. If available, abdominal ultrasound may diagnose or exclude appendicitis in some cases (see 'Ultrasound' above). Ultimately, surgical evaluation or exploration may be required if clinical suspicion for appendicitis is high but diagnostic evaluation is inconclusive (algorithm 1).

Clinical scoring systems — Clinical and laboratory data can be entered into one of many clinical scoring systems to calculate a clinical score, which predicts the likelihood of appendicitis. The risk category indicated by the clinical score can then be used to inform further decisions regarding imaging and/or treatment.

Alvarado score — While many clinical scoring systems have been proposed and validated for acute appendicitis [66-68], the modified Alvarado score is the most widely used [69,70].

The modified Alvarado scale assigns a score to each of the following diagnostic criteria (table 3):

●Migratory right lower quadrant pain (1 point)

●Anorexia (1 point)

●Nausea or vomiting (1 point)

●Tenderness in the right lower quadrant (2 points)

●Rebound tenderness in the right lower quadrant (1 point)

●Fever >37.5°C (>99.5°F) (1 point)

●Leukocytosis of white blood cell count >10 x 10⁹/L (2 points)

The score is obtained by summing the components. Higher values indicate higher probability of appendicitis. The maximum total score is 9. The original Alvarado score included left shift as an additional factor, resulting in a total score of 10 [69].

Scores of <4 and <5 have both been assessed as a cutoff for low risk of acute appendicitis in the literature and have resulted in an overall similarly low likelihood of acute appendicitis with either cutoff score [71,72]. For the purposes of triage, the score of <4 is selected for its potential to rule out appendicitis with greater certainty, given reported variability in the prevalence of acute appendicitis in patients with a score of 4 [71-73].

A low Alvarado score (<4) has more diagnostic utility to "rule out" appendicitis than a high score (≥7) does to "rule in" the diagnosis [10]. In a systematic review of 42 retrospective and prospective studies that included over 8300 patients with suspected acute appendicitis and/or right lower quadrant pain, 99 percent of patients with acute appendicitis had a score of >4 [71]. By contrast, a high score (≥7) alone had poor diagnostic utility as the overall specificity was 81 percent. Thus, the Alvarado score should be used to triage patients with a very low likelihood of acute appendicitis to evaluation for other causes of abdominal pain. Patients with a high Alvarado score should be further evaluated with imaging prior to treatment for appendicitis.

Initial triage in the diagnostic workup of appendicitis using Alvarado score is as follows:

●Patients with a score of 0 to 3 are unlikely to have appendicitis and should be treated for their symptoms. If the symptoms resolve and the patient feels well enough to go home, they may be discharged home with a plan to follow up with their primary care clinician or return to the emergency department if new symptoms arise. If the symptoms persist after a reasonable period of observation, they should be evaluated for other possible diagnoses (eg, by imaging or surgical evaluation). (See "Acute appendicitis in adults: Clinical manifestations and differential diagnosis", section on 'Differential diagnosis' and "Causes of abdominal pain in adults", section on 'Lower abdominal pain syndromes'.)

●Patients with a score of ≥4 should be evaluated further for appendicitis. In resource-limited settings where advanced imaging is not readily available, ultrasound may be the only available option. (See 'Ultrasound' above.)

Alternatively, the patient may be further observed, admitted, or undergo surgical evaluation. (See 'Surgical evaluation or exploration' below.)

Other clinical scoring systems — Worldwide, there are over 80 diagnostic tools for appendicitis, most relying on a clinician with access to laboratory values. The accuracy is high across the diagnostic tools [74]. Examples aside from the Alvarado score include:

●Appendicitis inflammatory response (AIR) score [75] – A randomized trial found that using an algorithm based on the AIR score reduced imaging, admission, and negative explorations compared with routine imaging [76]. A 2017 systematic review of 12 clinical scoring systems named the AIR score to be the best overall performer with high sensitivity (92 percent), specificity (63 percent), and area under curve values (0.84 to 0.97) [77].

●Adult appendicitis score (AAS) [78] – In a 2020 study of 5345 patients with right iliac fossa pain, the AAS performed best for women (cutoff score 8 or less, specificity 63.1 percent, failure rate 3.7 percent), whereas the AIR score performed best for men (cutoff score 2 or less, specificity 24.7 percent, failure rate 2.4 percent) [79].

The clinician can choose to use any clinical scoring system as long as it has been validated for the local population and can reliably risk stratify the patient into low- versus intermediate/high-risk categories based on preimaging evaluation. The performance of clinical scoring systems has been shown to vary by patient population and geography [16]. As an example, the RIPASA (Raja Isteri Pengiran Anak Saleha Appendicitis) score has been shown to achieve better sensitivity and specificity than the Alvarado score in Asian and Middle Eastern populations [80].

SURGICAL EVALUATION OR EXPLORATION — Surgical evaluation may be warranted if clinical suspicion for appendicitis is high but imaging studies are negative, nondiagnostic, or unavailable. Depending on the surgeon's assessment, the patient may be observed (with serial examinations or repeat imaging) or surgically explored.

If available, laparoscopic exploration is preferred to open appendectomy as it permits inspection of the entire peritoneal cavity and can achieve alternative diagnosis (eg, gynecological pathology) if the appendix is normal [29].

As discussed above, the proportion of appendicitis diagnosed intraoperatively or pathologically depends on the availability and local policy of imaging before surgical exploration. (See 'Standard versus selective imaging' above.)

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 adults".)

SUMMARY AND RECOMMENDATIONS

●Clinical and laboratory evaluation – Although clinical and laboratory parameters may be suggestive, none are sufficiently sensitive or specific to exclude or diagnose appendicitis.

•History – Clinical symptoms and signs suggestive of appendicitis include a history of central abdominal pain migrating to the right lower quadrant, anorexia, fever, and nausea/vomiting. (See 'Clinical evaluation' above and "Acute appendicitis in adults: Clinical manifestations and differential diagnosis".)

•Physical examination – On examination, right lower quadrant tenderness, along with classical signs of peritoneal irritation (eg, rebound tenderness, guarding, rigidity, referred pain), may be present. (See 'Clinical evaluation' above and "Acute appendicitis in children: Clinical manifestations and diagnosis".)

•Laboratory tests – The laboratory evaluation of suspected appendicitis should include white blood cells (WBC) with differential and serum C-reactive protein (CRP). A pregnancy test should be performed for women of childbearing age. (See 'Laboratory tests' above.)

●Diagnostic evaluation when CT is available – When available, we suggest performing contrast-enhanced abdominopelvic CT to diagnose appendicitis in nonpregnant adult patients (algorithm 1). CT is the most accurate, expeditious, and best tolerated imaging modality to diagnose appendicitis and has the added benefit of differentiating complicated from uncomplicated appendicitis or elucidating alternative diagnosis (table 2). (See 'Standard versus selective imaging' above.)

Abdominal ultrasound or MRI may be performed in young women (<30) who are particularly concerned about radiation risks. (See 'CT versus other image modalities' above.)

Imaging for appendicitis in children and pregnant women is discussed elsewhere. (See "Acute appendicitis in children: Diagnostic imaging" and "Acute appendicitis in pregnancy", section on 'Imaging'.)

●Diagnostic evaluation when CT is not available – When CT is not available, a clinical scoring system (eg, Alvarado score) can be used to identify patients with a very low likelihood of acute appendicitis and triage them to observation or evaluation for other causes of abdominal pain (table 3). When available, abdominal ultrasound may be performed for those who have intermediate or high clinical scores. The alternative is surgical evaluation and/or exploration (algorithm 1). (See 'Diagnostic evaluation when CT is not available' above.)

●Surgical evaluation – Surgical evaluation may be warranted if clinical suspicion for appendicitis is high but imaging studies are negative, nondiagnostic, or unavailable. Depending on the surgeon's assessment, the patient may be observed (with serial examinations or repeat imaging) or surgically explored. If available, laparoscopic exploration is preferred to open appendectomy as it permits inspection of the entire peritoneal cavity and can achieve alternative diagnosis (eg, gynecological pathology) if the appendix is normal. (See 'Surgical evaluation or exploration' above.)