Acute Appendicitis in Adults Diagnostic Evaluation

9/30/14, 22:17Acute appendicitis in adults: Diagnostic evaluation

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Official reprint from UpToDate www.uptodate.com 2014 UpToDate

AuthorRonald F Martin, MD

Section EditorMartin Weiser, MD

Deputy EditorKathryn A Collins, MD, PhD, FACS

Acute appendicitis in adults: Diagnostic evaluation

All topics are updated as new evidence becomes available and our peer review process is complete.Literature review current through: Aug 2014. | This topic last updated: Jul 24, 2014.

INTRODUCTION The diagnosis of acute appendicitis is typically based upon the findings from the medical historyand clinical examination and is supported by the laboratory and/or imaging findings.

This topic will review the diagnostic studies, including radiographic studies and laboratory tests that can assist inestablishing the diagnosis of acute appendicitis in the adult. The clinical manifestations of acute appendicitis and theoperative and nonoperative management are reviewed as separate topics. (See "Acute appendicitis in adults:Clinical manifestations and differential diagnosis" and "Acute appendicitis in adults: Management".)

DIAGNOSIS The diagnosis of acute appendicitis is generally made from the history and clinical examination; thediagnosis is supported by the laboratory and/or imaging findings. The patient presenting with acute abdominal painshould undergo a thorough physical examination, including a digital rectal examination. Women should undergo apelvic examination. (See "History and physical examination in adults with abdominal pain".)

An experienced examiner can make the correct diagnosis of appendicitis without imaging [1]. Several studies havefound the diagnostic accuracy of clinical evaluation alone to be 75 to 90 percent [2-5]. The diagnostic accuracy of theclinical examination may depend on the experience of the examining clinician [6-11]. Patients in whom appendicitis isconsidered to be extremely likely after assessment by an experienced clinician should proceed directly toappendectomy without further radiologic testing. (See "Acute appendicitis in adults: Management".)

The diagnosis of acute appendicitis can be difficult and a delay can result in perforation rates as high as 80 percent[12,13]. However, a retrospective review of 9048 adults with acute appendicitis found that the mean time frompresentation to operation (8.6 hours) was not associated with risk of perforation [14]. Factors associated withincreased risk of perforation included male gender (RR 1.24, 95% CI 1.08-1.43), increasing age (RR 1.04, 95% CI1.08-1.43), three or more comorbid illnesses (RR 2.8, 95% CI 1.36-3.49), and lack of medical insurance coverage(RR 1.43, 95% CI 1.24-1.66).

The challenging clinical settings include [15]:

No single feature or combination of features is a highly accurate predictor of acute appendicitis, although predictionrules based upon combinations of features may have some clinical utility [2,16-21].

Diagnostic scoring systems Several scoring systems have been proposed to standardize the correlation ofclinical and laboratory variables.

The Alvarado score is the most widely used diagnostic aid for the diagnosis of appendicitis and has been modifiedslightly since it was introduced [22,23]. However, clinical judgment remains paramount. For example, a low modifiedAlvarado score (



clinically suspicious appendicitis, in whom 53 patients (20 percent) had a final diagnosis of appendicitis, the lowmodified Alvarado score was less sensitive compared with unstructured clinical judgement (72 versus 93 percentsensitivity) [24]. A retrospective review of 74 patients with acute appendicitis found that the Alvarado score was lesssensitive and specific than CT imaging [25].

The modified Alvarado scale assigns a score to each of the following diagnostic criteria:

A low Alvarado score (37.5C (1 point)Leukocytosis (2 points)

A patient with a score of 0 to 3 could be considered to have a low risk of appendicitis and would be dischargedwith advice to return if there was no improvement in symptoms, subject to social circumstances.

A patient with a score of 4 to 6 would be admitted for observation and re-examination. If the score remains thesame after 12 hours, operative intervention is recommended.

A male patient with a score of 7 to 9 would proceed to appendectomy.

A female patient who is not pregnant with a score of 7 to 9 would undergo diagnostic laparoscopy, thenappendectomy if indicated by the intraoperative findings. The surgical management of appendicitis duringpregnancy is discussed separately. (See "Acute appendicitis in pregnancy".)



Based upon prospective trials and retrospective data, imaging studies do not improve the overall diagnostic accuracyfor acute appendicitis (image 1 and image 2); the diagnostic accuracy of an experienced surgeon is comparable toCT scan imaging in the assessment of patients with an equivocal presentation of acute appendicitis [2,4,5,7].However, in a retrospective review, the CT scan changed the treatment plan in 58 percent of patients [34].Differences in studies may, in part, be due to the experience of the surgeons and the populations being evaluated. Aprospective study of 2763 patients found that the sensitivity, specificity, positive predictive value, and negativepredictive value of preoperative evaluations included [5]:

Diagnostic imaging is unnecessary when the clinical diagnosis of acute appendicitis is nearly certain for eitherpresence or absence of appendicitis. Diagnostic imaging should be performed and is most likely to alter treatmentwhen the diagnosis of appendicitis is clinically suspected but unclear. Diagnostic imaging may be useful in children,elder adults, or women of childbearing age with an unclear presentation. Similarly, patients with comorbidities suchas diabetes, obesity, and immunocompromise may have a higher occurrence of atypical presentation of acuteappendicitis. These populations are more likely to present with unclear symptoms such as vague abdominal pain.(See "Acute appendicitis in children: Diagnostic imaging" and "Acute appendicitis in adults: Management", section on'Special considerations' and "Acute appendicitis in pregnancy", section on 'Diagnosis'.)

Computed tomography Based upon retrospective reviews, adult women are more than twice as likely asmen to have a nontherapeutic appendectomy for acute appendicitis [33,35-38], and, therefore, women may benefitfrom a preoperative CT scan if the diagnosis is uncertain (image 3 and image 4). A retrospective review of 1425consecutive patients undergoing an appendectomy found that adult women evaluated with a preoperative CT scanhad a significantly lower nontherapeutic appendectomy rate (NAR) compared with adult women without apreoperative diagnostic CT scan (21 versus 8 percent) [33]. There was no reduction in NAR for men or children.

Preoperative CT protocols for imaging include:

In most clinical settings, if there is sufficient diagnostic concern and uncertainty to warrant a CT scan to diagnoseappendicitis, a full abdominal-pelvic CT with IV and oral contrast should be performed or a decision should be madeto proceed to the operating room for abdominal exploration by laparotomy or laparoscopy.

Standard CT scan with contrast A commonly used protocol involves a standard abdominal and pelvic CTscan (16-MDCT or higher) with intravenous and oral contrast. (See "Principles of computed tomography of thechest".)

A number of findings suggest acute appendicitis on standard abdominal CT scanning [21,39,40]:

Ultrasonography 99.1, 91.7, 96.5, and 97.7 percent, respectively

Computed tomography96.4, 95.4, 95.6, and 96.3 percent, respectively

Clinical examination 99.0, 76.1, 88.1, and 97.6 percent, respectively

Standard abdominal-pelvic CT with IV and oral contrastFocused appendiceal CT with rectal contrastNoncontrast CT

Enlarged appendiceal diameter >6 mm with an occluded lumenAppendiceal wall thickening (>2 mm)Periappendiceal fat strandingAppendiceal wall enhancementAppendicolith (seen in approximately 25 percent of patients)



The sensitivity and specificity of CT with IV and oral contrast for acute appendicitis is in the range of 91 to 98 and 75to 93 percent, respectively [2,4,19,34,41-43]. Air in the appendix or a contrast-filled lumen in a normal appearingappendix virtually excludes the diagnosis. However, a nonvisualized appendix does not rule out appendicitis. This isparticularly important to remember in patients who have had symptoms for a short duration, since only minimalinflammatory changes may be present in the right lower quadrant.

An advantage of a complete abdominal CT scan is that it permits visualization of the entire abdomen. An alternativediagnosis is found in up to 15 percent of patients [34]. Furthermore, a CT scan can assist in the treatment plan forpatients with a palpable abdominal mass, such as those in whom an appendiceal phlegmon or abscess may havedeveloped. These features are more likely in patients who present after having prolonged symptoms (four to fivedays). (See "Acute appendicitis in adults: Management".)

A drawback of the standard CT protocol is that it takes up to two hours to administer oral contrast. In addition, a CTscan involves radiation exposure and intravenous contrast, with the potential for contrast-induced renal nephropathy.Cost and availability are also considerations, particularly in resource-poor settings.

Appendiceal CT A focused appendiceal CT scan can be performed with rectal contrast alone and thin cutsthrough the right iliac fossa. Because full oral contrast is not given, the scan can be performed within 15 minutes.Rectal contrast provides good visualization of the pericecal region without the need to wait for oral contrast to reachthe right lower quadrant, which may be an unpleasant procedure for the patient.

In a report using a limited appendiceal CT scan with rectal contrast, the sensitivity of the most common findings foracute appendicitis were as follows [21]:

One study reported that a focal appendiceal CT had 98 percent accuracy and sensitivity with rectal contrast along alimited area (15 cm) of the pelvis centered 3 cm superior to the cecal tip [17,44].

The relevance of focal appendiceal imaging is questionable outside of large medical centers, as this techniquerequires personnel to administer rectal contrast and a radiologist on site for the verification of positioning. In addition,an appendiceal CT scan only evaluates the appendix, and the images may be unrevealing in the presence of otherabdominal pathology.

Unenhanced CT The administration of contrast for imaging adds time, expense, and risk of an allergicreaction. A number of studies have suggested that adequate imaging can be obtained without contrast. In variousreports, unenhanced CT had a sensitivity of 88 to 96 percent, specificity of 91 to 98 percent, and diagnostic accuracyof 94 to 97 percent for appendicitis, with the added advantage of total exam time of 5 to 15 minutes [7,45,46].

Test characteristics may depend, at least in part, upon the patient's body habitus [2]. Some radiologists maintain thatif the BMI exceeds 25 that the CT is less accurate and therefore oral contrast is necessary.

An important limitation of unenhanced CT is the diminished ability to diagnose other abdominal pathology, potentiallydiminishing the role of the examination in patients in whom there is diagnostic uncertainty (eg, elder patients,women, atypical presentation).

Unenhanced CT may be of some value in patients who have renal failure or clinical instability. However, for mostpatients where there is sufficient diagnostic uncertainty to warrant a CT scan for appendicitis, a full abdominal-pelvicCT with IV and oral contrast should be performed or a decision should be made to proceed to the operating room forabdominal exploration.

Ultrasonography Ultrasound (US) is reliable to confirm the clinical diagnosis of acute appendicitis, but is notreliable to exclude the diagnosis (image 5 and image 6) [47]. Accuracy is diminished in obese patients.

Right lower abdominal quadrant fat stranding (100 percent sensitivity)Focal cecal thickening (69 percent specificity)Adenopathy (63 percent sensitivity)



At least eight sonographic findings suggestive of internal inflammatory changes of the appendix have been described[48-50]. The most accurate ultrasound finding for acute appendicitis is an appendiceal diameter of >6 mm with asensitivity, specificity, negative predictive value, and positive predictive value of 98 percent [49,50]. In variousreports, the sensitivity and specificity by US in the diagnosis of appendicitis ranged from 35 to 98 percent and 71 to98 percent, respectively [2,7,33,36].

Advantages of US compared with CT imaging include:

Disadvantages of US compared with CT imaging include:

Imaging costs The use of preoperative imaging studies in the diagnosis of acute appendicitis has increasedwith time, from 32 percent (1995 through 1999) to 95 percent (2001 through 2008), at one representative academicinstitution [33]. The increase in the use of CT scanning for the diagnosis of appendicitis has been largely justified bythe assumption that it decreases the rates of perforated appendicitis as well as nontherapeutic appendectomies[51,52]. In two studies that performed cost analysis, one showed that the cost of a nontherapeutic appendectomywas 16 times more expensive than a focused appendiceal CT scan, while another reported that an appendectomywas 22 times more expensive than nonenhanced CT scanning, implying cost savings if a reduction in nontherapeuticappendectomy rates could be achieved [46,53]. However, in one retrospective review, most patients undergoing anontherapeutic appendectomy had a preoperative CT scan, and more than 50 percent of those patients had CTinterpretations that were positive for, or could not exclude, acute appendicitis [33].

Several studies have failed to demonstrate a significant reduction in the overall institutional rates for nontherapeuticappendectomies despite the increased use of CT scan over time [19,34,35,37,41,54-56]. Results of studies thatincluded analysis of perforated appendicitis are mixed. One study showed an observed rate of appendicealperforation of 9 percent in patients who underwent routine CT imaging compared with 25 percent in patients in whomCT scanning was not used [37]. Other studies have demonstrated a fairly constant rate of perforated appendix overtime despite the increased use of CT scan [33,35,56].

Cost analysis for studies such as these is complicated by the value of CT scanning in patients in whom therapeuticappendectomy was performed; as a result, the cost savings depend upon an absolute rate reduction fornontherapeutic appendectomies [34,57]. Additionally, cost calculations depend upon local institutional variables andsurgeon variables; selected institutional observations may not be applicable to all practices.

Laboratory tests Laboratory tests serve a supportive role in the diagnosis of appendicitis. No single laboratorytest or combination of tests is an absolute marker for appendicitis [49,54].

A complete blood count (CBC) with a differential should be obtained, but cannot be used to confirm or exclude thediagnosis of appendicitis. A mild leukocytosis and a left shift (increase in total white blood cell count, bands[immature neutrophils], and neutrophils) can be present in acute appendicitis as well as other acute etiologies ofabdominal pain.

A pregnancy test should be performed for all women of childbearing age.

Although mild elevations in serum bilirubin (total bilirubin >1.0 mg/dL) have been noted to be a marker forappendiceal perforation with a sensitivity of 70 percent and a specificity of 86 percent [58], the test is notdiscriminatory and generally not helpful in the evaluation of patients suspected of acute appendicitis.

Results may be obtained more efficiently (institution and practitioner dependent)No radiation exposureNo use of intravenous or intestinal contrast agents

Less diagnostic accuracyLess likely to reveal an accurate alternative diagnosisAccuracy is operator dependentTechnical challenges: Patients with a large body habitus and/or a large amount of overlying bowel gas



Exploratory laparotomy/laparoscopy The acceptable nontherapeutic appendectomy rate (NAR) variesdepending upon the age and sex of the patient. For example, in young healthy males with right lower quadrant pain,the negative appendectomy rate (NAR) should be less than 10 percent, while a rate that approaches 20 percent isreasonable in young women in whom other pelvic processes can make accurate diagnosis more difficult (eg, pelvicinflammatory diseases, tubo-ovarian abscess) [45,59].

No significant difference in NAR was noted in comparing laparoscopic and open appendectomy [33]. A low NAR hasbeen achieved in some centers that use close in-hospital observation [60].

SUMMARY

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REFERENCES

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The constellation of findings from history, physical examination, and laboratory studies will usually lead anexperienced examiner to the correct diagnosis of appendicitis without diagnostic imaging (see 'Diagnosis'above). A clinical diagnosis can be more challenging in women, who may benefit from the addition of radiologicimaging when the diagnosis is unclear.

The patient presenting with acute abdominal pain should undergo a thorough physical examination, including adigital rectal examination. Women should undergo a pelvic examination. (See 'Diagnosis' above and "Historyand physical examination in adults with abdominal pain".)

Based upon prospective trials and retrospective data, imaging studies do not improve the overall diagnosticaccuracy for acute appendicitis (image 1 and image 2); the diagnostic accuracy of an experienced surgeon iscomparable to CT scan imaging in the assessment of patients with an equivocal presentation of acuteappendicitis. (See 'Imaging' above.)

Diagnostic imaging is advised when the diagnosis of appendicitis is suspected but unclear (eg, elderly patients,patients with comorbid illnesses, women of childbearing age). In this clinical setting, we perform a standardabdominal CT scan with intravenous and oral contrast. (See 'Standard CT scan with contrast' above.)

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GRAPHICS

CT scan equivocal appendicitis

The patient is a 56-year-old male who presents with right lower quadrant pain. The CT scanof the lower abdomen in the axial plane (A) and the magnified view of the appendix (B) showa normal sized appendix with surrounding induration (red arrow). The periappendicealinduration raises the possibility of appendicitis. The associated thickening of the posteriorperitoneum (orange arrow) suggests an acute process in the right lower quadrant. However,the epicenter of induration (yellow arrow in A and B) in the region of the tip of the liver (L)and ascending colon (C) suggests that the process likely originates in that region. Thus theprocess around the appendix is secondary and not primary to the appendix.

Graphic 83554 Version 1.0



Ultrasound equivocal appendicitis

The gray scale ultrasound of the appendix is projected in the longitudinal (A) and transverseplanes (B). The appearance of the appendix is near normal except for a diameter thatmeasures 7.6 mm in the long axis, and a diameter that measures between 7 and 9 mm in thetransverse plane. Since this diameter should be 6 mm or less, the diagnosis of appendicitis isentertained. There is no loculated fluid around the appendix and no free fluid present in theperitoneal cavity. The echogenic line of the mucosa and submucosa is intact and the lumen isdistended with complex material (arrow). The findings of the enlarged diameter with no otherspecific pathognomonic features make the diagnosis of acute appendicitis equivocal.




CT scan normal appendix

CT scan depicts a normal appendix. The figure on the left shows an appendiceal lumencontaining air and wall thickness of 3 mm (yellow arrow). The figure on the right shows thetip of the normal appendix (green arrow) that measures 6 mm and no associated induration.




CT scan acute appendicitis

The CT scan was obtained using oral and intravenous contrast from a patient who presentedwith right lower quadrant abdominal pain. These figures show an inflammed appendix thatmeasures 21 mm in diameter and contains an appendicolith and fluid that is likely purulent.(A) Shows an appendicolith in the appendix using a white arrow.(B) Shows the appendicolith, an overlay of orange to show fluid inside the appendix, and ayellow arrow indicates free fluid.(C) Shows the enlarged appendix and fluid without an overlay.(D) Shows a colored overlay: red circle depicts the enhancing appendiceal wall; orangedepicts the intra-appendiceal fluid; yellow depicts the free fluid.




Normal appendix on ultrasound

Ultrasound image of a normal appendix (red arrow and markers). Theappendix is located at the confluence of the taenia coli (white arrows)and is seen in relationship to the cecum (COE). Fluid filled small bowel(DD) and iliac vessels (VI) are also indicated.

Courtesy of Christoph F Dietrich, MD.




Doppler ultrasound of appendicitis

In this doppler ultrasound image of appendicitis, the appendix appearsedematous (9 x 8 mm) and hypervascular. The layers of the wall arestill detectable. Continued inflammation may be followed by localizedischemia (which may be visualized by color Doppler imaging) andnecrosis. Sonographic findings were confirmed at surgery.

Courtesy of Christoph F Dietrich, MD.




Disclosures: Ronald F Martin, MD Nothing to disclose. Martin Weiser, MD Nothing to disclose. Kathryn A Collins, MD, PhD, FACSEmployee of UpToDate, Inc.Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through amulti-level review process, and through requirements for references to be provided to support the content. Appropriately referencedcontent is required of all authors and must conform to UpToDate standards of evidence.Conflict of interest policy

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Acute Appendicitis in Adults Diagnostic Evaluation

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