Diagnostic value of unenhanced helical CT in adult patients with suspected acute appendicitis

Imaging of Gastrointestinal Tract Ailments

Gastrointestinal (GI) disorders comprise a diverse range of conditions that can significantly reduce the quality of life and can even be life-threatening in serious cases. The development of accurate and rapid detection approaches is of essential importance for early diagnosis and timely management of GI diseases. This review mainly focuses on the imaging of several representative gastrointestinal ailments, such as inflammatory bowel disease, tumors, appendicitis, Meckel's diverticulum, and others. Various imaging modalities commonly used for the gastrointestinal tract, including magnetic resonance imaging (MRI), positron emission tomography (PET) and single photon emission computed tomography (SPECT), and photoacoustic tomography (PAT) and multimodal imaging with mode overlap are summarized. These achievements in single and multimodal imaging provide useful guidance for improved diagnosis, staging, and treatment of the corresponding gastrointestinal diseases. The review evaluates the strengths and weaknesses of different imaging techniques and summarizes the development of imaging techniques used for diagnosing gastrointestinal ailments.

Near miss abdominal pain

An 18-year-old adolescent with intermittent colicky abdominal pain for 4 months was admitted to a Medical Emergency Assessment Unit for further investigation of possible colitis, after being reviewed by a surgeon in Accident and Emergency. Initially he was treated for a urinary tract infection, however a CT of the abdomen revealed appendicular perforation with pelvic abscess formation. The patient required an urgent laparoscopy and was discharged without complications. Typically, appendicitis is an acute surgical problem whereas chronic abdominal pain is routinely considered a medical problem. This case demonstrates the importance of maintaining acute causes as part of the differentials list in young patients with unexplained recurrent abdominal pain as well as justifying the early use of CT when there is ambiguity surrounding a diagnosis.

Discovery of Urinary Proteomic Signature for Differential Diagnosis of Acute Appendicitis

Acute appendicitis is one of the most common acute abdomens, but the confident preoperative diagnosis is still a challenge. In order to profile noninvasive urinary biomarkers that could discriminate acute appendicitis from other acute abdomens, we carried out mass spectrometric experiments on urine samples from patients with different acute abdomens and evaluated diagnostic potential of urinary proteins with various machine-learning models. Firstly, outlier protein pools of acute appendicitis and controls were constructed using the discovery dataset (32 acute appendicitis and 41 control acute abdomens) against a reference set of 495 normal urine samples. Ten outlier proteins were then selected by feature selection algorithm and were applied in construction of machine-learning models using naïve Bayes, support vector machine, and random forest algorithms. The models were assessed in the discovery dataset by leave-one-out cross validation and were verified in the validation dataset (16 acute appendicitis and 45 control acute abdomens). Among the three models, random forest model achieved the best performance: the accuracy was 84.9% in the leave-one-out cross validation of discovery dataset and 83.6% (sensitivity: 81.2%, specificity: 84.4%) in the validation dataset. In conclusion, we developed a 10-protein diagnostic panel by the random forest model that was able to distinguish acute appendicitis from confusable acute abdomens with high specificity, which indicated the clinical application potential of noninvasive urinary markers in disease diagnosis.

Systematic Review: The Role of Intravenous and Oral Contrast in the Computed Tomography Evaluation of Acute Appendicitis

BACKGROUND

This systematic review provides practicing emergency physicians updated information regarding the role of oral and intravenous contrast in the computed tomography (CT) evaluation of acute appendicitis.

METHODS

A PubMed literature search was conducted from January 1, 1996 to December 31, 2018 and limited to human clinical trials written in English with relevant keywords. High-quality studies were identified and then underwent a structured review. Recommendations are made based on the literature review.

RESULTS

Fifty-seven articles met criteria for rigorous review, of which 14 were appropriate for citation in this review. Excellent evidence shows that oral contrast does not improve the test characteristics of CT with intravenous contrast (IVCT) in the evaluation of adults suspected of having acute appendicitis. Good evidence shows that noncontrast abdominal CTs have excellent test characteristics for this same group of patients.

CONCLUSIONS

Considering its downsides and lack of utility, the medical literature does not support using oral contrast in the evaluation of acute appendicitis. There is no direct evidence showing that IVCT is better than a noncontrast CT in the evaluation of acute appendicitis; however, the available literature is consistent with slightly better test characteristics for IVCTs. Still, if IVCT cannot be obtained in a timely manner, noncontrast CTs are extremely accurate in detecting this disease.

Computed tomography for diagnosis of acute appendicitis in adults

BACKGROUND

Diagnosing acute appendicitis (appendicitis) based on clinical evaluation, blood testing, and urinalysis can be difficult. Therefore, in persons with suspected appendicitis, abdominopelvic computed tomography (CT) is often used as an add-on test following the initial evaluation to reduce remaining diagnostic uncertainty. The aim of using CT is to assist the clinician in discriminating between persons who need surgery with appendicectomy and persons who do not.

OBJECTIVES

Primary objective Our primary objective was to evaluate the accuracy of CT for diagnosing appendicitis in adults with suspected appendicitis. Secondary objectives Our secondary objectives were to compare the accuracy of contrast-enhanced versus non-contrast-enhanced CT, to compare the accuracy of low-dose versus standard-dose CT, and to explore the influence of CT-scanner generation, radiologist experience, degree of clinical suspicion of appendicitis, and aspects of methodological quality on diagnostic accuracy.

SEARCH METHODS

We searched MEDLINE, Embase, and Science Citation Index until 16 June 2017. We also searched references lists. We did not exclude studies on the basis of language or publication status.

SELECTION CRITERIA

We included prospective studies that compared results of CT versus outcomes of a reference standard in adults (> 14 years of age) with suspected appendicitis. We excluded studies recruiting only pregnant women; studies in persons with abdominal pain at any location and with no particular suspicion of appendicitis; studies in which all participants had undergone ultrasonography (US) before CT and the decision to perform CT depended on the US outcome; studies using a case-control design; studies with fewer than 10 participants; and studies that did not report the numbers of true-positives, false-positives, false-negatives, and true-negatives. Two review authors independently screened and selected studies for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently collected the data from each study and evaluated methodological quality according to the Quality Assessment of Studies of Diagnostic Accuracy - Revised (QUADAS-2) tool. We used the bivariate random-effects model to obtain summary estimates of sensitivity and specificity.

MAIN RESULTS

We identified 64 studies including 71 separate study populations with a total of 10,280 participants (4583 with and 5697 without acute appendicitis). Estimates of sensitivity ranged from 0.72 to 1.0 and estimates of specificity ranged from 0.5 to 1.0 across the 71 study populations. Summary sensitivity was 0.95 (95% confidence interval (CI) 0.93 to 0.96), and summary specificity was 0.94 (95% CI 0.92 to 0.95). At the median prevalence of appendicitis (0.43), the probability of having appendicitis following a positive CT result was 0.92 (95% CI 0.90 to 0.94), and the probability of having appendicitis following a negative CT result was 0.04 (95% CI 0.03 to 0.05). In subgroup analyses according to contrast enhancement, summary sensitivity was higher for CT with intravenous contrast (0.96, 95% CI 0.92 to 0.98), CT with rectal contrast (0.97, 95% CI 0.93 to 0.99), and CT with intravenous and oral contrast enhancement (0.96, 95% CI 0.93 to 0.98) than for unenhanced CT (0.91, 95% CI 0.87 to 0.93). Summary sensitivity of CT with oral contrast enhancement (0.89, 95% CI 0.81 to 0.94) and unenhanced CT was similar. Results show practically no differences in summary specificity, which varied from 0.93 (95% CI 0.90 to 0.95) to 0.95 (95% CI 0.90 to 0.98) between subgroups. Summary sensitivity for low-dose CT (0.94, 95% 0.90 to 0.97) was similar to summary sensitivity for standard-dose or unspecified-dose CT (0.95, 95% 0.93 to 0.96); summary specificity did not differ between low-dose and standard-dose or unspecified-dose CT. No studies had high methodological quality as evaluated by the QUADAS-2 tool. Major methodological problems were poor reference standards and partial verification primarily due to inadequate and incomplete follow-up in persons who did not have surgery.

AUTHORS' CONCLUSIONS

The sensitivity and specificity of CT for diagnosing appendicitis in adults are high. Unenhanced standard-dose CT appears to have lower sensitivity than standard-dose CT with intravenous, rectal, or oral and intravenous contrast enhancement. Use of different types of contrast enhancement or no enhancement does not appear to affect specificity. Differences in sensitivity and specificity between low-dose and standard-dose CT appear to be negligible. The results of this review should be interpreted with caution for two reasons. First, these results are based on studies of low methodological quality. Second, the comparisons between types of contrast enhancement and radiation dose may be unreliable because they are based on indirect comparisons that may be confounded by other factors.

Size matters: Computed tomographic measurements of the appendix in emergency department scans

BACKGROUND

Radiologists use a size cutoff in appendiceal diameter to assist surgeons in diagnosing appendicitis, however, no consensus exists as to the size of a normal adult appendix. We aim to evaluate radial appendiceal diameter on CT in adult patients both with and without appendicitis.

METHODS

Retrospective review of adults who underwent abdominal CT was performed. Variables collected include: demographics, BMI, WBC count at presentation, radial diameter of appendix (mm), presence of fat stranding, fecalith, and free fluid.

RESULTS

During the study period, 3099 patients underwent CT. The appendix was visualized on 74% of scans. Mean appendiceal diameter was 6.6 mm (±1.7). The appendix was larger in patients with appendicitis (6.6 vs. 11.4; p < 0.0001). Overall appendectomy incidence was 3.2%. Sensitivity and specificity of CT in diagnosing appendicitis in this cohort of patients were 90% and 94%. NPV was 99.5%.

CONCLUSION

While appendiceal diameter was larger in patients with appendicitis, >20% of patients without appendicitis had an appendiceal diameter >7 mm. Diameter alone should not be relied upon to diagnose appendicitis.

Accuracy and reliability of tablet computer as an imaging console for detection of radiological signs of acute appendicitis using PACS workstation as reference standard

PURPOSE

To ascertain the accuracy and reliability of tablet as an imaging console for detection of radiological signs of acute appendicitis [on focused appendiceal computed tomography (FACT)] using Picture Archiving and Communication System (PACS) workstation as reference standard.

METHODS

From January, 2014 to June, 2015, 225 patients underwent FACT at our institution. These scans were blindly re-interpreted by an independent consultant radiologist, first on PACS workstation and, two weeks later, on tablet. Scans were interpreted for the presence of radiological signs of acute appendicitis. Accuracy of tablet was calculated using PACS as reference standard. Kappa (κ) statistics were calculated as a measure of reliability.

RESULTS

Of 225 patients, 99 had radiological evidence of acute appendicitis on PACS workstation. Tablet was 100% accurate in detecting radiological signs of acute appendicitis. Appendicoliths, free fluid, lymphadenopathy, phlegmon/abscess, and perforation were identified on PACS in 90, 43, 39, 10, and 12 scans, respectively. There was excellent agreement between tablet and PACS for detection of appendicolith (к = 0.924), phlegmon/abscess (к = 0.904), free fluid (к = 0.863), lymphadenopathy (к = 0.879), and perforation (к = 0.904).

CONCLUSIONS

Tablet computer, as an imaging console, was highly reliable and was as accurate as PACS workstation for the radiological diagnosis of acute appendicitis.

Minimally Invasive Treatment for Appendiceal Mass Formed After Acute Perforated Appendicitis

The optimal treatment for appendiceal mass formed after appendiceal rupture due to acute appendicitis is surrounded with controversy. The treatment strategy ranges from open surgery (emergency or interval appendectomy), laparoscopic appendectomy, and image-guided drainage, to conservative treatment with or without antibiotics. Nonsurgical treatment (including conservative and drainage treatment), followed by interval appendectomy to prevent recurrence, is the traditional management of these patients. The need for interval appendectomy after a successful conservative or/and image-guided drainage treatment, has recently been questioned as the risk of recurrence is relatively small. Several authors consider that even in cases involving only ambulatory follow-up observation, without interval surgery after conservative management, the recurrence rate and risks of missing underlying pathologies were not high. This article evaluates the minimally invasive treatment modalities in the management of appendiceal mass, risk of undetected serious disease, and the need for interval appendectomy to prevent recurrence.

Acute Bowel Computed Tomography

Acute abdominal pain is a common presenting complaint in the emergency department. Increasingly, computed tomography is utilized for evaluating these patients. Radiologists are therefore expected to be familiar with the pertinent clinical and radiologic information related to acute bowel pathology. This primer will review the need-to-know and latest updates related to computed tomography evaluation of acute bowel pathology.

Diagnostic Accuracy of Noncontrast CT in Detecting Acute Appendicitis: A Meta-analysis of Prospective Studies

The aim of the study is to evaluate the diagnostic accuracy of noncontrast CT in detecting acute appendicitis. Prospective studies in which noncontrast CT was performed to evaluate acute appendicitis were found on PubMed, EMBASE, and Cochrane Library. Pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio were assessed. The summary receiver-operating characteristic curve was conducted and the area under the curve was calculated. Seven original studies investigating a total of 845 patients were included in this meta-analysis. The pooled sensitivity and specificity were 0.90 (95% CI: 0.86–0.92) and 0.94 (95% CI: 0.92–0.97), respectively. The pooled positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio was 12.90 (95% CI: 4.80–34.67), 0.09 (95% CI: 0.04–0.20), and 162.76 (95% CI: 31.05–853.26), respectively. The summary receiver-operating characteristic curve was symmetrical and the area under the curve was 0.97 (95% CI: 0.95–0.99). In conclusion, noncontrast CT has high diagnostic accuracy in detecting acute appendicitis, which is adequate for clinical decision making.

Comparison of multislice computed tomography and clinical scores for diagnosing acute appendicitis

Objective

To compare Raja Isteri Pengiran Anak Saleha Appendicitis (RIPASA) and Alvarado scores with multislice computed tomography (MSCT) for diagnosing acute appendicitis (AA).

Methods

This retrospective study included patients with abdominal pain who had undergone MSCT, and whose medical notes included RIPASA and Alvarado score parameters. MSCT was compared with RIPASA and Alvarado scores for diagnosing AA.

Results

Of 297 patients included, sensitivity, specificity and accuracy for diagnosing AA were 95.2%, 73.6% and 87.2% for RIPASA score (cutoff value 7.5) and 63.1%, 80.9% and 69.7% for Alvarado score (cutoff value 7). Sensitivity, specificity and accuracy of MSCT for diagnosing AA were 98.9%, 96.4% and 98.0%, respectively. In terms of accuracy, statistically significant differences were observed between RIPASA and Alvarado scores, and between MSCT and RIPASA scores. The mean RIPASA score was significantly different in the simple AA group (9.7 ± 2.2) compared with other AA groups (10.5 ± 1.7). No statistically significant difference was observed in RIPASA score between nonperforated and perforated AA. MSCT sensitivity, specificity and accuracy for diagnosing simple AA were 94.1%, 96.4% and 95.8%, respectively; for differentiating perforated and nonperforated AA, scores were 90.2%, 95.2% and 94.1%, respectively.

Conclusion

MSCT is the optimum diagnostic tool for AA, followed by RIPASA score and Alvarado score, particularly in diagnosing simple and perforated AA.

Mandatory imaging cuts costs and reduces the rate of unnecessary surgeries in the diagnostic work-up of patients suspected of having appendicitis

OBJECTIVE

To evaluate whether mandatory imaging is an effective strategy in suspected appendicitis for reducing unnecessary surgery and costs.

METHODS

In 2010, guidelines were implemented in The Netherlands recommending the mandatory use of preoperative imaging to confirm/refute clinically suspected appendicitis. This retrospective study included 1,556 consecutive patients with clinically suspected appendicitis in 2008-2009 (756 patients/group I) and 2011-2012 (800 patients/group II). Imaging use (none/US/CT and/or MRI) was recorded. Additional parameters were: complications, medical costs, surgical and histopathological findings. The primary study endpoint was the number of unnecessary surgeries before and after guideline implementation.

RESULTS

After clinical examination by a surgeon, 509/756 patients in group I and 540/800 patients in group II were still suspected of having appendicitis. In group I, 58.5% received preoperative imaging (42% US/12.8% CT/3.7% both), compared with 98.7% after the guidelines (61.6% US/4.4% CT/ 32.6% both). The percentage of unnecessary surgeries before the guidelines was 22.9%. After implementation, it dropped significantly to 6.2% (p<0.001). The surgical complication rate dropped from 19.9% to 14.2%. The average cost-per-patient decreased by 594 <euro> from 2,482 to 1,888 <euro> (CL:-1081; -143).

CONCLUSION

Increased use of imaging in the diagnostic work-up of patients with clinically suspected appendicitis reduced the rate of negative appendectomies, surgical complications and costs.

KEY POINTS

• The 2010 Dutch guidelines recommend mandatory imaging in the work-up of appendicitis. • This led to a considerable increase in the use of preoperative imaging. • Mandatory imaging led to reduction in unnecessary surgeries and surgical complications. • Use of mandatory imaging seems to reduce health care costs.

Can outer-to-outer diameter be used alone in diagnosing appendicitis on 128-slice MDCT?

AIM: To assess the frequency of visualization, position and diameter of normal appendix on 128-slice multidetector computed tomography (MDCT) in adult population.

METHODS: Retrospective cross sectional study conducted at Radiology Department, Dallah Hospital, Riyadh, Saudi Arabia from March 2013 to October 2013. Non-enhanced computed tomography scans of abdomen and pelvis of 98 patients presenting with hematuria (not associated with abdominal pain, fever or colonic disease) were reviewed by two radiologists, blinded to patient history. The study group included 55 females and 43 males with overall mean age of 54.7 years (range 21 to 94 years). The coronal reformatted images were reviewed in addition to the axial images. The frequency of visualization of appendix was recorded with assessment of position, diameter and luminal contents.

RESULTS: The appendix was recorded as definitely visualized in 99% of patients and mean outer-to-outer diameter of the appendix was 5.6 ± 1.3 mm (range 3.0-11.0 mm).

CONCLUSION: MDCT with its multiplanar reformation display is extremely useful for visualization of normal appendix. The normal appendix is very variable in its position and diameter. In the absence of other signs, the diagnosis of acute appendix should not be made solely on outer-to-outer appendiceal diameter.

The normal appendix on CT: does size matter?

PURPOSE

(1) To evaluate the frequency of visualisation and measurements of the normal appendix. (2) To correlate Body Mass Index (BMI) and gender with visualisation of the normal appendix. (3) To correlate age, gender and body length with appendiceal length.

MATERIALS AND METHODS

A retrospective review of 186 patients undergoing abdominal CT without suspicion of acute appendicitis was done. Frequency of visualisation and measurements (including maximal outer diameter, wall thickness, length, content, location of base and tip) of normal appendices were recorded.

RESULTS

Prevalence of appendectomy was 34.4%. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of visualisation of the normal appendix were 76%, 94%, 96%, 67%, and 82% respectively. The mean maximal diameter of the appendix was 8.19 mm±1.6 (SD) (range, 4.2-12.8 mm). The mean length of the appendix was 81.11 mm±28.44 (SD) (range, 7.2-158.8 mm). The mean wall thickness of the appendix was 2.22 mm±0.56 (SD) (range, 1.15-3.85 mm). The most common location of the appendiceal tip was pelvic in 66% appendices. The most common location of the appendiceal base was inferior, medial, and posterior in 37%. The normal appendix contained high-density material in 2.2%. There was a significant correlation between gender and appendiceal length, with men having longer appendices than women.

CONCLUSION

Most normal appendices are seen at multislice CT using i.v. contrast. The maximal outer diameter of the normal appendix overlaps with values currently used to diagnose appendicitis on CT.

Improvement in the diagnosis of appendicitis

Our attempts to systematically improve accuracy in the evaluation of patients with suspected appendicitis are, in some ways, hindered by the fact that the condition is so frequently straightforward to diagnose. Careful history-taking and physical examination are reliable in most patients. However, establishing the diagnosis with these skills alone remains vulnerable to conditions that masquerade as acute appendicitis. A substantial body of clinical research over the last quarter-century has shown that improved accuracy is possible. Strategies for improvement include the use of diagnostic scoring systems, laboratory makers such as CRP, diagnostic laparoscopy, and advanced imaging modalities such as CT, MRI, and US. How clinicians use these strategies depends on many factors related to practice setting, the population served, and clinical goals. In children, for instance, the desire to limit exposure to ionizing radiation competes with the greater anatomic detail that a CT scan can provide; at the same time, many hospitals that treat children do not have the resources to maintain the sort of full-time, highly sophisticated abdominal US programs that achieve the highest rates of diagnostic accuracy in clinical studies. Trade-offs have to be made, but improvement is possible in almost all groups of patients: the clinical community should no longer settle for a 15% NA rate when 5% is clearly possible without adverse consequences. Many clinicians will be faced with the task of evaluating patients suspected of having acute appendicitis. A deliberate, proactive, and, ideally, benchmarked strategy for improving diagnosis should be the standard to which we hold ourselves and the promise we deliver to our patients.

Does limiting oral contrast decrease emergency department length of stay?

Introduction:

The purpose of this study was to examine the impact on emergency department (ED) length of stay (LOS) of a new protocol for intravenous (IV)-contrast only abdominal/pelvic computed tomography (ABCT) compared to historical controls.

Methods:

This was a retrospective case-controlled study performed at a single academic medical center. Patients ≥ 18 undergoing ABCT imaging for non-traumatic abdominal pain were included in the study. We compared ED LOS between historical controls undergoing ABCT imaging with PO/IV contrast and study patients undergoing an IV-contrast-only protocol. Imaging indications were the same for both groups and included patients with clinical suspicion for appendicitis, diverticulitis, small bowel obstruction, or perforation. We identified all patients from the hospital’s electronic storehouse (imaging code, ordering department, imaging times), and we abstracted ED LOS and disposition from electronic medical records.

Results:

Two hundred and eleven patients who underwent PO/IV ABCT prep were compared to 184 patients undergoing IV-contrast only ABCT prep. ED LOS was shorter for patients imaged with the IV-contrast only protocol (4:35 hrs vs. 6:39 hrs, p < 0.0001).

Conclusion:

Implementation of an IV-contrast only ABCT prep for select ED patients presenting for evaluation of acute abdominal pain significantly decreased ED LOS.

Evaluation of normal appendix vermiformis in adults with multidetector computed tomography

To determine the utility of different contrast enhancement phases (unenhanced, arterial, and venous), slice thicknesses (0.5, 3, and 5 mm), and planes (axial and coronal) in the evaluation of appendix vermiformis (AV) on multidetector computed tomography (MDCT), CT examinations of 600 patients were obtained. No significant difference was found between the different imaging planes, slice thicknesses, and contrast enhancement phases in terms of detection rates of AV. The mean diameter of AV in the axial plane (5.93±0.06 mm) was significantly lower than that in the coronal plane (6.18±0.06 mm). Evaluation of AV on MDCT is enhanced by combined interpretation on axial and coronal planes.

Clinical policy: Critical issues in the evaluation and management of emergency department patients with suspected appendicitis

This clinical policy from the American College of Emergency Physicians is an update of a 2000 clinical policy on the evaluation and management of patients presenting with nontraumatic acute abdominal pain.1 A writing subcommittee reviewed the literature to derive evidence-based recommendations to help clinicians answer the following critical questions: (1)Can clinical findings be used to guide decision making in the risk stratification of patients with possible appendicitis? (2) In adult patients with suspected acute appendicitis who are undergoing a computed tomography scan, what is the role of contrast? (3) In children with suspected acute appendicitis who undergo diagnostic imaging, what are the roles of computed tomography and ultrasound in diagnosing acute appendicitis?Evidence was graded and recommendations were given based on the strength of the available data in the medical literature.

Diagnostic accuracy of noncontrast computed tomography for appendicitis in adults: a systematic review

STUDY OBJECTIVE

We seek to determine the diagnostic test characteristics of noncontrast computed tomography (CT) for appendicitis in the adult emergency department (ED) population.

METHODS

We conducted a search of MEDLINE, EMBASE, the Cochrane Library, and the bibliographies of previous systematic reviews. Included studies assessed the diagnostic accuracy of noncontrast CT for acute appendicitis in adults by using the final diagnosis at surgery or follow-up at a minimum of 2 weeks as the reference standard. Studies were included only if the CT was completed using a multislice helical scanner. Two authors independently conducted the relevance screen of titles and abstracts, selected studies for the final inclusion, extracted data, and assessed study quality. Consensus was reached by conference, and any disagreements were adjudicated by a third reviewer. Unenhanced CT test performance was assessed with summary receiver operating characteristic curve analysis, with independently pooled sensitivity and specificity values across studies.

RESULTS

The search yielded 1,258 publications; 7 studies met the inclusion criteria and provided a sample of 1,060 patients. The included studies were of high methodological quality with respect to appropriate patient spectrum and reference standard. Our pooled estimates for sensitivity and specificity were 92.7% (95% confidence interval 89.5% to 95.0%) and 96.1% (95% confidence interval 94.2% to 97.5%), respectively; the positive likelihood ratio=24 and the negative likelihood ratio=0.08.

CONCLUSION

We found the diagnostic accuracy of noncontrast CT for the diagnosis of acute appendicitis in the adult population to be adequate for clinical decisionmaking in the ED setting.

Noncontrast and contrast enhanced computed tomography for diagnosing acute appendicitis: A retrospective study for the usefulness

Abdominal computed tomography (CT) provides great benefits for the differential diagnosis in patients complaining of acute abdominal pain. However, the use of diagnostic X-rays is associated with the cumulative risk of cancer development. In order to determine the relative usefulness of noncontrast and enhanced CT with intravenous contrast material for diagnosing acute appendicitis, the retrospective analysis was performed using 247 patients (46 children and 201 adults) with clinically suspected appendicitis, who were admitted to our hospital from 2002 to 2006 and underwent noncontrast or combined noncontrast and enhanced CT examination. Of 185 patients who were diagnosed to have acute appendicitis with appendiceal thickening (167 cases) or normal-sized appendix (18 cases), 73 cases underwent noncontrast CT alone and these 73 cases could be retrospectively diagnosed to have appendicitis on noncontrast CT. On the other hand, 112 cases of these 185 patients underwent noncontrast CT followed by enhanced CT, and vermiform appendix was detected in 86 cases of them (86/112, 76.8%) on noncontrast CT. These 86 cases could be retrospectively diagnosed to have acute appendicitis on noncontrast CT, whereas enhanced CT was required to detect vermiform appendix and to obtain the final diagnosis of appendicitis in the remaining 26 cases (26/112, 23.2%). Enhanced CT was superior to noncontrast CT in diagnosing appendicitis in all age and any gender groups. We suggest that enhanced, but not noncontrast, CT should be primarily performed for diagnosing acute appendicitis in all patients to minimize the radiation exposure unless intravenous administration of contrast material is contraindicated.

Computed tomography evaluation of the normal appendix: comparison of low-dose and standard-dose unenhanced helical computed tomography

OBJECTIVE

To determine the visualization rate of the normal appendix on low- and standard-dose unenhanced computed tomography (CT) and to evaluate the variables that may influence the identification of the appendix.

METHODS

The study population was derived from the previous study, approved by the internal review board, investigating the effectiveness of low-dose CT (LDCT) in diagnosis of urolithiasis. Sixty-eight patients presenting with acute flank pain underwent 2 unenhanced dual-slice CT examinations. Standard-dose CT (SDCT) scans were obtained using 2 x 5-mm collimation, 120 kVp, and 170 effective mAs and followed by LDCT using 30 or 50 effective mAs. Two independent board-certified radiologists retrospectively recorded the visualization, outer diameter, and the wall thickness of normal appendices. The diameters, circumference, and cross-sectional area of the abdomen were measured.

RESULTS

The prevalence of appendectomy was 8.8% (6 of 68 patients). The means of the 2 reviewers' sensitivity, specificity, positive and negative predictive values, and accuracy for visualization of normal appendix at SDCT versus LDCT respectively were 78% versus 73%, 100% versus 92%, 100% versus 99%, 31% versus 24%, and 80% versus 74% (P = 0.39-0.75). The interobserver agreement was good at both SDCT (kappa = 0.61) and LDCT (kappa = 0.74). Overall 40% to 58% of appendices at LDCT and 33% to 47% at SDCT was larger than 6 mm. There was no significant correlation in the appendix visualization neither with abdominal dimensions nor with visceral or pericecal fat at both dose sets. The calculated mean effective radiation dose at LDCT was 70% to 82% less than SDCT.

CONCLUSIONS

Low- and standard-dose nonenhanced helical CT can visualize a normal appendix with high accuracy and good interobserver agreement. The diameter of normal appendix overlaps with that of appendicitis at CT. A diameter of 10.0 mm should be considered as the upper limit of normal in the absence of any other CT signs of appendicitis.

Current Concepts in Imaging of Appendicitis

Appendicitis is the most common cause of acute abdominal pain requiring surgery. Early diagnosis is crucial to the success of therapy. CT and ultrasound are widely recognized as very useful in the timely diagnosis of appendicitis. MR imaging is emerging as an alternative to CT in pregnant patients and in patients who have an allergy to iodinated contrast material. This article reviews the current imaging methods and diagnostic features of appendicitis.

Acute appendicitis: diagnostic value of nonenhanced CT with selective use of contrast in routine clinical settings

The purposes of this study were to determine the (1) frequency with which nonenhanced computed tomography (CT) (NECT) permits conclusive diagnosis of acute appendicitis, (2) accuracy of NECT when findings are conclusive, and (3) overall accuracy of a CT protocol consisting of NECT with selective use of contrast. Five hundred and thirty-six patients underwent a NECT protocol with selective use of contrast. Diagnostic accuracy was then determined separately for (1) patients with conclusive initial NECT, (2) patients with inconclusive initial NECT, and (3) all patients. NECT was conclusive on initial interpretation in 404/536 patients and inconclusive in 132/536. Of 132 inconclusive studies, 126 were repeated with contrast (intravenous, oral or rectal). Sensitivity, specificity, and positive and negative predictive value for diagnosis of acute appendicitis were (1) 90%, 96.0%, 84.8%, and 97.4% in patients with conclusive NECT (n = 404); (2) 95.6%, 92.3%, 73%, and 99% in patients with inconclusive NECT followed by repeat CT with contrast; and (3) 91.3%, 95%, 82%, and 98% in all patients. The initial diagnosis of appendicitis may be made by NECT in 75% of patients, with contrast administration reserved for inconclusive NECT studies.

US or CT for Diagnosis of Appendicitis in Children and Adults? A Meta-Analysis

PURPOSE

To perform a meta-analysis to evaluate the diagnostic performance of ultrasonography (US) and computed tomography (CT) for the diagnosis of appendicitis in pediatric and adult populations.

MATERIALS AND METHODS

Medical literature (from 1986 to 2004) was searched for articles on studies that used US, CT, or both as diagnostic tests for appendicitis in children (26 studies, 9356 patients) or adults (31 studies, 4341 patients). Prospective and retrospective studies were included if they separately reported the rate of true-positive, true-negative, false-positive, and false-negative diagnoses of appendicitis from US and CT findings compared with the positive and negative rates of appendicitis at surgery or follow-up. Clinical variables, technical factors, and test performance were extracted. Three readers assessed the quality of studies.

RESULTS

Pooled sensitivity and specificity for diagnosis of appendicitis in children were 88% (95% confidence interval [CI]: 86%, 90%) and 94% (95% CI: 92%, 95%), respectively, for US studies and 94% (95% CI: 92%, 97%) and 95% (95% CI: 94%, 97%), respectively, for CT studies. Pooled sensitivity and specificity for diagnosis in adults were 83% (95% CI: 78%, 87%) and 93% (95% CI: 90%, 96%), respectively, for US studies and 94% (95% CI: 92%, 95%) and 94% (95% CI: 94%, 96%), respectively, for CT studies.

CONCLUSION

From the diagnostic performance perspective, CT had a significantly higher sensitivity than did US in studies of children and adults; from the safety perspective, however, one should consider the radiation associated with CT, especially in children.

Tomografia computadorizada sem contraste intravenoso no abdome agudo: quando e por que usar

A tomografia computadorizada sem contraste intravenoso tem sido freqüentemente proposta na avaliação inicial de pacientes com suspeita de abdome agudo, ocupando o espaço de outros métodos diagnósticos. Os autores apresentam uma revisão bibliográfica dos principais aspectos e eficácia da tomografia computadorizada sem contraste intravenoso no diagnóstico de apendicite aguda, cólica nefrética, diverticulite, pancreatite aguda, apendicite epiplóica, pneumoperitônio e obstrução intestinal. Discutem quais as vantagens e limitações desta técnica de exame, bem como seus aspectos práticos.

Diagnosis of appendicitis in adults by ultrasonography or computed tomography: a systematic review and meta-analysis

OBJECTIVES

The use of ultrasonography and computed tomography (CT) in the diagnosis of appendicitis in adult patients was compared.

METHODS

Systematic review and meta-analysis of current evidence in two clinical situations: unselected nonpregnant, adult patients with symptoms of appendicitis, and more selective use in only those patients who still have an equivocal diagnosis subsequent to routine clinical investigations.

RESULTS

Meta-analysis of eligible studies shows CT to have better sensitivity and specificity than ultrasound in both clinical situations.

CONCLUSIONS

Application of these findings in clinical practice and/or policy would need to evaluate the better diagnostic performance of CT against its cost and availability. In addition, it is imperative that future studies be conducted in patient populations that are well-defined with respect to prior investigations. Sequelae of false-negative and false-positive diagnoses should also be evaluated.

A systematic review of whether oral contrast is necessary for the computed tomography diagnosis of appendicitis in adults

BACKGROUND

There are several methods of contrast administration when performing computed tomography (CT) scanning for suspected appendicitis. In this systematic review we evaluated the diagnostic performance of CT with and without contrast material.

METHODS

Twenty-three reports were identified using a Medline search.

RESULTS

The aggregated diagnostic performance characteristics of all modes of CT scanning were excellent with a range of sensitivity (83--97%), specificity (93--98%), positive predictive value (86--98%), negative predictive value (94--99%), and accuracy (92--97%). The diagnostic performance of CT without oral contrast was similar (sensitivity, 95% vs. 92% [not statistically significant]; negative predictive value, 96% for both protocols) or surprisingly better (specificity, 97% vs. 94%; positive predictive value, 97% vs. 89%; accuracy, 96% vs. 92%; P<.0001) than with oral contrast.

CONCLUSIONS

Noncontrast CT techniques to diagnose appendicitis showed equivalent or better diagnostic performance compared with CT scanning with oral contrast. A prospective comparative trial of CT with and without oral contrast for appendicitis should be performed to assess the adequacy of this modality.

Comparison of US and unenhanced multi-detector row CT in patients suspected of having acute appendicitis

PURPOSE

To prospectively compare the diagnostic performance of ultrasonography (US) and unenhanced multi-detector row computed tomography (CT) in patients suspected of having acute appendicitis by using surgery or clinical follow-up as the reference standard.

MATERIALS AND METHODS

The institutional review board approved the research protocol. Written informed consent was obtained from all patients or, for those who were adolescents, from their parents. Ninety-four patients (59 female and 35 male patients) aged 16-81 years (mean, 38 years) who were suspected of having acute appendicitis underwent both US and unenhanced multi-detector row CT of the entire abdomen. The examinations were performed within 1-2 hours of each other. US and CT images were obtained and prospectively interpreted by a different radiologist from a group of abdominal radiologists or a group of residents and general radiologists. Radiologists proposed an overall diagnosis and an alternative diagnosis. Data from US and CT were compared, and the definite diagnosis was established with surgical findings (n = 40) or results of clinical follow-up (n = 54) as the reference standard. Comparisons were made for each group of radiologists and the patient's age, body mass index (BMI), and sex. Proportion comparisons were made by using the Pearson chi2 test or the Fisher exact test. Continuous variables were compared between groups with the Mann-Whitney U test.

RESULTS

Thirty patients had definite appendicitis. The sensitivity, specificity, positive and negative predictive values, and accuracy were not significantly different between US and CT or between groups of radiologists (P values ranged from .389 to >.99), regardless of the patient's BMI (P values ranged from .073 to >.99). Misclassifications were compared with the definite alternative diagnosis and were not significantly different between US and CT or between groups of radiologists (P = .061-.592), regardless of patient age (P = .875) or sex (P = .151 and >.99 for male and female patients, respectively). The frequency of inconclusive examinations, however, was significantly higher with US than with CT, regardless of radiologist experience (P = .020 and <.001, respectively).

CONCLUSION

Although the diagnostic performances of US and multi-detector row CT are comparable, more inconclusive images were obtained with US.

CT Evaluation of Appendicitis and Its Complications: Imaging Techniques and Key Diagnostic Findings

OBJECTIVE

This article reviews various CT protocols for appendicitis, identifies key CT findings for diagnosing appendicitis, discusses unusual manifestations such as chronic and recurrent appendicitis, and profiles imaging features that differentiate appendicitis from other inflammatory and neoplastic ileocecal conditions. Patients were studied with helical CT.

CONCLUSION

CT is a highly accurate, noninvasive test for appendicitis, but the optimal CT technique is controversial. Major complications of appendicitis (perforation, abscess formation, peritonitis, bowel obstruction, septic seeding of mesenteric vessels, gangrenous appendicitis) and their management are discussed. Abdominal CT is a well-established technique in the study of acute abdominal pain and has shown high sensitivity and specificity for diagnosing and differentiating appendicitis, providing an accurate diagnosis in the early stages of disease.

CT appearance of the normal appendix in adults

The aims of this study were to identify (1) the normal range of the appendix on computed tomography (CT), (2) the correlation of patient age and sex with the visibility and appearance of the appendix on CT, and (3) the normal variations in wall thickness, intraluminal content, and location of the appendix. Three hundred seventy-two outpatients underwent abdominopelvic CT. The scans were reviewed on the picture archiving and communication system and appendiceal outer-to-outer wall diameter, wall thickness, location, content and its correlation with appendix diameter were analyzed. The appendix was visualized in 305/372 patients. Its location relative to the cecum was highly variable. The diameter range was 3-10 mm; in 42% of cases the diameter was greater than 6 mm. When the intraluminal content (185/305) was visualized, the diameter was slightly superior to the mean (p=0.0156). In 329 CT scans in which oral contrast material was given, the appendix was filled by contrast material in 74/329 patients. The appendix wall thickness was measurable in 22/305 patients (average 0.15 cm). There is significant overlap between the normal and abnormal CT appearance of the appendix. Consequently the diagnosis of acute appendicitis should be based not only on the appearance of the appendix but also on the presence of secondary signs.

Current surgical opinion of computed tomography for acute appendicitis

BACKGROUND

Appendiceal computed tomography (CTA) for the diagnosis of acute appendicitis (AA) has become popular, with a growing body of literature reporting excellent rates of sensitivity, specificity, and accuracy (S/S/A). However, several studies indicate that the true S/S/A of CTA is lower than the best results reported, especially if the white blood count is normal, the reader is inexperienced, or the study is obtained in the absence of surgical consultation. Thus, it is possible that skepticism of the value of CTA to diagnose AA may exist. Our objective was to determine the current knowledge of and attitudes regarding CTA among practicing surgeons.

METHODS

Two thousand questionnaires were sent randomly to general surgeon Fellows of the American College of Surgeons. Questions detailed the surgeon's practice, experience, hospital characteristics, and opinion regarding the utility and use of CTA. The existence of a formal CTA protocol, its characteristics, and radiologist availability for CT interpretation were determined. Data were analyzed by x(2) with Fisher exact test, multiple-group x(2), and univariate ANOVA as appropriate. Results are reported as mean +/- SEM with significance accepted at p < 0.05.

RESULTS

The response rate was 27%. Mean age was 51 +/- 1 years, 60% of respondents were general surgeons, and 9% were laparoscopic surgeons. Seventy-four percent of respondents believe the accuracy rate of CTA is less than the originally reported 98%; those who disbelieve are less likely to utilize CTA (p < 0.0001). Sixty-two percent of respondents believe CTA is over-utilized; 43% obtain CTA in </=25% of patients, and 62% obtain CTA in fewer than 50% of patients. Only 36% of respondents had access to CTA by protocol; those surgeons were more likely to know protocol details (p < 0.0001). Emergency medicine physicians order CTA most often (63%), and studies are most often interpreted by an attending radiologist (69%).

CONCLUSIONS

Practicing surgeons are skeptical of the role of CTA for diagnosis of AA. Incorporation of CTA into practice is not widespread, perhaps because CTA by protocol is unavailable to most surgeons and because it is often obtained in the absence of surgical consultation.

Acute Appendicitis: Comparison of Low-Dose and Standard-Dose Unenhanced Multi–Detector Row CT

PURPOSE

To prospectively compare low- and standard-dose unenhanced multi-detector row computed tomography (CT) in patients suspected of having acute appendicitis.

MATERIALS AND METHODS

Ninety-five consecutive patients underwent two unenhanced multi-detector row CT examinations with 4 x 2.5-mm collimation, 120 kVp, and 30 and 100 effective mAs. Two radiologists independently read the images obtained at each dose during two sessions. Readers recorded visualization of the appendix and presence of gas in its lumen, appendicolith, periappendiceal fat stranding, cecal wall thickening, and abscess or phlegmon to measure the diameter of the appendix and to propose diagnosis (appendicitis or alternative). Data were compared according to dose and reader, with definite diagnosis established on basis of surgical findings (n = 37) or clinical follow-up. chi(2) tests and logistic regression were used. Measurement agreements were assessed with Cohen kappa statistics.

RESULTS

Twenty-nine patients had a definite diagnosis of appendicitis. No difference was observed between the frequency of visualization of the appendix (P =.874) neither in its mean diameter (P =.101-.696, according to readers and sessions) nor in the readers' overall diagnosis (P =.788) at each dose. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of each sign were not different between doses. Fat stranding, appendicolith, and diameter were the most predictive signs, regardless of dose, yielding approximately 90% of correct diagnoses. The ability to propose a correct alternative diagnosis was not influenced by the dose.

CONCLUSION

Low-dose unenhanced multi-detector row CT has similar diagnostic performance as standard-dose unenhanced multi-detector row CT for the diagnosis of acute appendicitis.

The acute right lower quadrant

Acute right lower quadrant pain is a nonspecific but common clinical complaint. Appendicitis is the most common cause of acute right lower quadrant pain and CT has become the most reliable imaging method in the evaluation of these patients. Although there is controversy regarding the best way to perform CT in this setting, oral and i.v. contrast-enhanced CT remains the most commonly used technique. CT with oral and i.v. contrast material facilitates diagnosis of appendicitis and the numerous other entities that may cause right lower quadrant pain.