Low vs. standard dose computed tomography in suspected acute appendicitis: Is it time for a change?

Low-Dose Abdominal CT for Evaluating Suspected Appendicitis: Recommendations for CT Imaging Techniques and Practical Issues

A vast disparity exists between science and practice for CT radiation dose. Despite high-level evidence supporting the use of low-dose CT (LDCT) in diagnosing appendicitis, a recent survey showed that many care providers were still concerned that the low image quality of LDCT may lead to incorrect diagnoses. For successful implementation of LDCT practice, it is important to inform and educate the care providers not only of the scientific discoveries but also of concrete guidelines on how to overcome more practical matters. Here, we discuss CT imaging techniques and other practical issues for implementing LDCT practice.

Low-Dose Abdominal CT for Evaluating Suspected Appendicitis in Adolescents and Young Adults: Review of Evidence

Due to its excellent diagnostic performance, CT is the mainstay of diagnostic test in adults with suspected acute appendicitis in many countries. Although debatable, extensive epidemiological studies have suggested that CT radiation is carcinogenic, at least in children and adolescents. Setting aside the debate over the carcinogenic risk of CT radiation, the value of judicious use of CT radiation cannot be overstated for the diagnosis of appendicitis, considering that appendicitis is a very common disease, and that the vast majority of patients with suspected acute appendicitis are adolescents and young adults with average life expectancies. Given the accumulated evidence justifying the use of low-dose CT (LDCT) of only 2 mSv, there is no reasonable basis to insist on using radiation dose of multi-purpose abdominal CT for the diagnosis of appendicitis, particularly in adolescents and young adults. Published data strongly suggest that LDCT is comparable to conventional dose CT in terms of clinical outcomes and diagnostic performance. In this narrative review, we will discuss such evidence for reducing CT radiation in adolescents and young adults with suspected appendicitis.

Diagnostic accuracy using low-dose versus standard radiation dose CT in suspected acute appendicitis: prospective cohort study

BACKGROUND

Contrast-enhanced CT is the reference standard used in diagnostic imaging for acute appendicitis in adults. The radiation dose has been of concern. This study aimed to assess whether a lower radiation dose would affect the diagnostic accuracy of CT.

METHODS

This was a prospective single-centre cohort study of patients (aged over 16 years) with suspected appendicitis evaluated for enrolment in concurrent APPAC II-III trials. The diagnostic accuracy of contrast-enhanced low- and standard-dose CT was compared with study protocols guiding imaging based on BMI; this enabled direct CT imaging comparison only in patients with a BMI below 30 kg/m2. The on-call CT diagnosis was compared with the final clinical diagnosis.

RESULTS

Among all 856 patients investigated, the accuracy of low-dose (454 patients) and standard-dose (402 patients) CT in identifying patients with and without appendicitis was 98·0 and 98·5 per cent respectively. In patients with a BMI under 30 kg/m2, respective values were 98·2 per cent (434 patients) and 98·6 per cent (210 patients) (P = 1·000). The corresponding accuracy for differentiating between uncomplicated and complicated acute appendicitis was 90·3 and 87·6 per cent in all patients, and 89·8 and 88·4 per cent respectively among those with a BMI below 30 kg/m2 (P = 0·663). The median radiation dose in the whole low- and standard-dose CT groups was 3 and 7 mSv respectively. In the group with BMI below 30 kg/m2, corresponding median doses were 3 and 5 mSv (P < 0·001).

CONCLUSION

Low- and standard-dose CT were accurate both in identifying appendicitis and in differentiating between uncomplicated and complicated acute appendicitis. Low-dose CT was associated with a significant radiation dose reduction, suggesting that it should be standard clinical practice at least in patients with a BMI below 30 kg/m2.

Final diagnosis and patient disposition following equivocal results on 2-mSv CT vs. conventional-dose CT in adolescents and young adults with suspected appendicitis: a post hoc analysis of large pragmatic randomized trial data

OBJECTIVE

To compare 2-mSv CT and conventional-dose CT (CDCT, typically 7-8 mSv) regarding final diagnosis and patient disposition following equivocal CT results in adolescents and young adults with suspected appendicitis.

METHODS

In total, 3074 patients of 15-44 years (28 ± 9 years, 1672 women) from 20 hospitals were randomized to undergo contrast-enhanced 2-mSv CT (n = 1535) or CDCT (n = 1539) from December 2013 through August 2016. One hundred sixty-one radiologists prospectively rated the likelihood of appendicitis in a Likert scale (i.e., grades 1-5). The final diagnosis was based on CT image, surgical, pathologic, and clinical findings. Post hoc analysis was performed for final diagnosis, surgical procedure, and delay in patient management following equivocal results (i.e., grade 3).

RESULTS

The 2-mSv CT and CDCT groups were comparable for final diagnosis following equivocal results, including confirmed appendicitis (1.2% [18 patients] vs. 1.2% [19], p > 0.99), negative appendectomy (0.1% [2] vs. 0.3% [4], p = 0.53), and perforated appendicitis (0.1% [1] vs. 0.2% [3], p = 0.53). More patients were confirmed as not having appendicitis following equivocal results in the CDCT group than in the 2-mSv CT group (2.2% [34] vs. 1.0% [16], p = 0.016). The two groups were comparable for the need of appendectomy (1.4% [22] vs. 1.5% [23], p > 0.99), need of additional imaging tests (0.7% [11] vs. 1.1% [17], p = 0.35), and delay in patient management following equivocal results.

CONCLUSION

2-mSv CT is comparable to CDCT regarding final diagnosis and patient disposition following equivocal CT results.

KEY POINTS

• Our results strengthen evidence justifying the use of low-dose CT instead of conventional-dose CT (CDCT) in adolescents and young adults with suspected appendicitis. • The 2-mSv CT and CDCT groups were comparable for final diagnosis following equivocal CT results, including confirmed appendicitis (1.2% vs. 1.2%, p > 0.99), negative appendectomy (0.1% vs. 0.3%, p = 0.53), and perforated appendicitis (0.1% vs. 0.2%, p = 0.53). • The two groups were comparable for the need for appendectomy (1.4% vs. 1.5%, p > 0.99), need for additional imaging tests (0.7% vs. 1.1%, p = 0.35), and delay in patient management, following equivocal CT results.

Diagnosis of Uncomplicated and Complicated Appendicitis in Adults

Background:

Diagnostic work-up of acute appendicitis remains challenging. While some guidelines advise to use a risk stratification based on clinical parameters, others use standard imaging in all patients. As non-operative management of uncomplicated appendicitis has been identified as feasible and safe, differentiation between uncomplicated and complicated appendicitis is of paramount importance. We reviewed the literature to describe the optimal strategy for diagnosis of acute appendicitis.

Methods:

A narrative review about the diagnosis of acute appendicitis in adult patients was conducted. Both diagnostic strategies and goals were analyzed.

Results:

For diagnosing acute appendicitis, both ruling in and ruling out the disease are important. Clinical and laboratory findings individually do not suffice, but when combined in a diagnostic score, a better risk prediction can be made for having acute appendicitis. However, for accurate diagnosis imaging seems obligatory in patients suspected for acute appendicitis. Scoring systems combining clinical and imaging features may differentiate between uncomplicated and complicated appendicitis and may enable ruling out complicated appendicitis. Within conservatively treated patients with uncomplicated appendicitis, predictive factors for non-responsiveness to antibiotics and recurrence of appendicitis need to be defined in order to optimize treatment outcomes.

Conclusion:

Standard imaging increases the diagnostic power for both ruling in and ruling out acute appendicitis. Incorporating imaging features in clinical scoring models may provide better differentiation between uncomplicated and complicated appendicitis. Optimizing patient selection for antibiotic treatment of appendicitis may minimize recurrence rates, resulting in better treatment outcomes.

The Accuracy of Low-dose Computed Tomography Protocol in Patients With Suspected Acute Appendicitis: The OPTICAP Study

OBJECTIVE

To compare diagnostic accuracy of contrast enhanced low-dose computed tomography (CT) accomplished in the OPTICAP trial phantom phase to standard CT in patients with suspected acute appendicitis.

BACKGROUND

Increasing use of CT as the gold standard in diagnosing acute appendicitis has raised concerns regarding radiation exposure. Unenhanced low-dose CT protocols have shown similar diagnostic accuracy with standard CT for diagnosing appendicitis. To our knowledge, there are no other trials in which the same patient with suspected acute appendicitis underwent both standard and low-dose CT allowing interpatient comparison.

METHODS

OPTICAP is an interpatient protocol sequence randomized noninferiority single-center trial performed at Turku University Hospital between November, 2015 and August, 2016. Sixty patients with suspected acute appendicitis and body mass index <30 kg/m were enrolled to undergo both standard and low-dose contrast enhanced CT scans, which were categorized as normal, uncomplicated or complicated appendicitis by 2 radiologists in blinded manner. All patients with CT confirmed appendicitis underwent appendectomy to obtain histopathology.

RESULTS

The low-dose protocol was not inferior to standard protocol in terms of diagnostic accuracy; 79% [95% confidence interval (CI) 66%-89%) accurate diagnosis in low-dose and 80% (95% CI 67%-90%) in standard CT by primary radiologist. Accuracy to categorize appendicitis severity was 79% for both protocols. The mean radiation dose of low-dose CT was significantly lower compared with standard CT (3.33 and 4.44 mSv, respectively).

CONCLUSION

Diagnostic accuracy of contrast enhanced low-dose CT was not inferior to standard CT in diagnosing acute appendicitis or distinguishing between uncomplicated and complicated acute appendicitis in patients with a high likelihood of acute appendicitis. Low-dose CT enabled significant radiation dose reduction.

Randomized control trial comparing an Alvarado Score-based management algorithm and current best practice in the evaluation of suspected appendicitis

BACKGROUND

An objective algorithm for the management of suspected appendicitis guided by the Alvarado Score had previously been proposed. This algorithm was expected to reduce computed tomography (CT) utilization without compromising the negative appendectomy rate. This study attempts to validate the proposed algorithm in a randomized control trial.

METHODS

A randomized control trial comparing the management of suspected acute appendicitis using the proposed algorithm compared to current best practice, with the rate of CT utilization as the primary outcome of interest. Secondary outcomes included the percentage of missed diagnosis, negative appendectomies, length of stay in days, and overall cost of stay in dollars.

RESULTS

One hundred sixty patients were randomized. Characteristics such as age, ethnic group, American Society of Anesthesiologist score, white cell count, and symptom duration were similar between the two groups. The overall CT utilization rate of the intervention arm and the usual care arm were similar (93.7% vs 92.5%, p = 0.999). There were no differences in terms of negative appendectomy rate, length of stay, and cost of stay between the intervention arm as compared to the usual care arm (p = 0.926, p = 0.705, and p = 0.886, respectively). Among patients evaluated with CT, 75% (112 out of 149) revealed diagnoses for the presenting symptoms.

CONCLUSION

The proposed AS-based management algorithm did not reduce the CT utilization rate. Outcomes such as missed diagnoses, negative appendectomy rates, length of stay, and cost of stay were also largely similar. CT utilization was prevalent as 93% of the study cohort was evaluated by CT scan.

TRIAL REGISTRATION

The study has been registered at ClinicalTrials.gov (NCT03324165, Registered October 27 2017).

Diagnostic sensitivity and specificity of 2-mSv CT vs. conventional-dose CT in adolescents and young adults with suspected appendicitis: post hoc subgroup analysis of the LOCAT data

OBJECTIVES

To test whether the difference in sensitivity or specificity between 2-mSv CT and conventional-dose CT (CDCT) for the diagnosis of appendicitis differs across subgroups of adolescents and young adults with suspected appendicitis.

MATERIALS AND METHODS

We used the per-protocol analysis data of a trial conducted between Dec 2013 and Aug 2016, including 2773 patients (median age [interquartile range], 28 [21-35] years) and 160 radiologists from 20 hospitals. We defined subgroups by sex, body size, clinical risk scores for appendicitis, time of CT examination (i.e., working vs. after hours), CT machines, radiologists' experience, previous site experience in 2-mSv CT, and site practice volume. We drew forest plots and tested for additive or multiplicative interaction between radiation dose and subgroup attributes. If any subgroup had fewer than 200 patients, we considered the results from that subgroup not meaningful.

RESULTS

For most subgroups, the 95% CIs for the differences in sensitivity and specificity were 4.0 percentage points or narrower and contained the minute overall between-group differences. There was no significant interaction on sensitivity or specificity. A few subgroups, including those of extreme body sizes, high appendicitis inflammatory response scores, and hospitals with small appendectomy volume, were regarded to have insufficient numbers of patients.

CONCLUSIONS

There was no notable subgroup heterogeneity, which implies that 2-mSv CT can replace CDCT in diverse populations. Further studies are needed for the subgroups for which we had only small data.

KEY POINTS

• The minute difference in sensitivity or specificity between the 2-mSv CT and conventional-dose CT (typically 7 mSv) groups were consistent across various patient or hospital characteristics. • These results indicate that 2-mSv CT can replace conventional-dose CT in diverse populations. • Further studies are needed to confirm whether 2-mSv CT can replace conventional-dose CT in patients of extreme body sizes, high appendicitis inflammatory response scores, or hospitals with small appendectomy volume, as those subgroups in our data included limited numbers of patients.

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.

Laparoscopic appendectomy for acute appendicitis: How to discourage surgeons using inadequate therapy

Acute appendicitis (AA) develops in a progressive and irreversible manner, even if the clinical course of AA can be temporarily modified by intentional medications. Reliable and real-time diagnosis of AA can be made based on findings of the white blood cell count and enhanced computed tomography. Emergent laparoscopic appendectomy (LA) is considered as the first therapeutic choice for AA. Interval/delayed appendectomy at 6-12 wk after disease onset is considered as unsafe with a high recurrent rate during the waiting time. However, this technique may have some advantages for avoiding unnecessary extended resection in patients with an appendiceal mass. Non-operative management of AA may be tolerated only in children. Postoperative complications increase according to the patient’s factors, and temporal avoidance of emergent general anesthesia may be beneficial for high-risk patients. The surgeon’s skill and cooperation of the hospital are important for successful LA. Delaying appendectomy for less than 24 h from diagnosis is safe. Additionally, a semi-elective manner (i.e., LA within 24 h after onset of symptoms) may be paradoxically acceptable, according to the factors of the patient, physician, and institution. Prompt LA is mandatory for AA. Fortunately, the Japanese government uses a universal health insurance system, which covers LA.

Comparison of Low- and Standard-Dose CT for the Diagnosis of Acute Appendicitis: A Meta-Analysis

OBJECTIVE

A meta-analysis was performed to compare low-dose CT and standard-dose CT in the diagnosis of acute appendicitis with an emphasis on diagnostic value.

MATERIALS AND METHODS

A systematic literature search for articles published through June 2016 was performed to identify studies that compared low-dose CT with standard-dose CT for the evaluation of patients suspected of having acute appendicitis. Summary estimates of sensitivity and specificity with 95% CIs were calculated using a bivariate random-effects model. Meta-regression was used to perform statistical comparisons of low-dose CT and standard-dose CT.

RESULTS

Of 154 studies, nine studies investigating a total of 2957 patients were included in this meta-analysis. The pooled sensitivity and specificity of low-dose CT were 96.25% (95% CI, 91.88-98.31%) and 93.22% (95% CI, 88.75-96.00%), respectively. The pooled sensitivity and specificity of standard-dose CT were 96.40% (95% CI, 93.55-98.02%) and 92.17% (95% CI, 88.24-94.86%), respectively. In a joint model estimation of meta-regression, lowand standard-dose CT did not show a statistically significant difference (p = 0.71). Both lowand standard-dose CT seem to be characterized by high positive and negative predictive values across a broad spectrum of pretest probabilities for acute appendicitis.

CONCLUSION

Low-dose CT is highly effective for the diagnosis of suspected appendicitis and can be considered a valid alternative first-line imaging test that reduces the potential risk of exposure to ionizing radiation.